Table of Contents Advanced Diesel Technology Subject Page Advanced Diesel Technology Introduction.9 U.S. Market Diesel Introduction .9 A Diesel Engine for North America.10 Technical Data Comparison .11 Power Output Comparison .12 Diesel vs. N52.12 Diesel vs. N54.12 Comparison to the V8 Engine.13 Engine Mechanical.16 Engine Mechanical Changes .16 Bearings.16 Pistons.16 Crankcase .16 Crankcase Vent.17 Summary of Changes for the M57D30T2 (US).18 Vehicle Specific Diesel Changes.20 Diesel Vehicles for the US Market.20 Transmission.20 Twin Damper Torque Converter .20 Rear Differential .21 Cooling System .22 Initial Print Date: 08/08 Revision Date: 09/08 Table of Contents Subject Page Cooling Method .23 Climate Control for Diesel Vehicles .24 Front PTC Pin Assignments .25 PTC Heater E90.25 Acoustic Package.26 Diesel Engine Management.28 Engine Control Module .28 Sensors and Actuators.29 OBD Monitored Functions .30 Diesel Oxidation Catalyst .30 SCR Catalytic Converter.30 Supplying Urea-water Solution .31 Level Measurement in Active Reservoir .31 Suitable Urea-water Solution.31 NO x Sensors.32 Exhaust Gas Recirculation (EGR) .32 Diesel Particulate Filter (DPF) .33 Air Intake and Exhaust Systems.34 Air Intake Systems .36 Swirl Flaps.37 Exhaust System.38 EGR System .38 Fuel System .44 Fuel Supply Overview .44 Table of Contents Subject Page Fuel Tank.45 E70 Fuel Tank.45 E90 Fuel Tank.46 Fuel Tank Functions .46 Fuel Delivery from Fuel Tank .47 Air Supply and Extraction .48 Fuel Filler Cap.48 Misfueling Protection .49 Fuel Pump .50 Fuel Pump - E90 .51 Screw-spindle Pump - E70 .51 Low Pressure Fuel System - E90.52 Fuel Temperature Sensor.52 Fuel Filter Heating - E90 .53 Low Pressure Fuel System - E70.54 Fuel Pressure-temperature Sensor .54 Fuel Filter Heating - E70 .55 High Pressure Fuel System .56 Fuel Injectors.57 Piezo Injector Operation.58 Injector Opening.58 Injector Closing.58 Coupler Module.59 Leakage Oil.59 Restrictor.60 Fuel Injector Volume Adjustment .61 Table of Contents Subject Page Volume Adjustment.61 Zero Volume Adaptation.61 Mean Volume Adaptation.62 Diesel Emission Control Systems.74 Legislation .74 Exhaust Gas Recirculation.76 Low Pressure EGR.76 Exhaust Turbocharger.78 High Pressure EGR .79 Selective Catalytic Reduction.80 SCR Overview - Simplified.81 SCR System Components.82 Component Location - E70.82 Component Location - E90.83 Passive Reservoir.84 Level Sensors.85 Venting.85 Transfer Unit .85 Active Reservoir.86 Function Unit .87 Level Sensor.88 Delivery Unit .89 Pump .89 Pressure Sensor.89 Reversing Valve .89 Metering Module and Mixer.90 Table of Contents Subject Page Mixer.90 NO x Sensors.91 Functions of the SCR System.92 Chemical Reaction.93 Conversion of the Urea-water Solution .93 NO x Reduction.95 SCR Control .96 Metering Strategy .97 Metering System Control.98 Metering of the Urea-water Solution .98 Supplying Urea-water Solution .99 Heater.99 Transfer Pumping .101 Delivery .102 Evacuating .103 Level Measurement.104 Level Calculation .105 SCR System Modes.106 INIT (SCR initialization) .106 STANDBY (SCR not active) .106 NOPRESSURECONTROL (waiting for enable for pressure control).106 PRESSURECONTROL (SCR system running) .107 PRESSUREREDUCTION.108 AFTERRUN.108 Table of Contents Subject Page Warning and Shut-down Scenario.110 Warning Scenario .110 Shut-down Scenario.Ill Exhaust Fluid Incorrect.Ill Refilling .112 Refilling in Service Workshop .112 Topping Up.112 Diesel Exhaust Fluid .112 Health and Safety .112 Materials Compatibility.113 Storage and Durability .113 Service Concerns .113 Temperature Conversion Table .114 Diesel Auxiliary Systems.116 Glow-plug System .116 Preheating.117 Start Standby Heating.117 Start Heating.117 Emergency Heating .118 Concealed Heating .118 Partial Load Heating .118 Actuation and Fault Detection.118 Table of Contents Subject Page 8 Advanced Diesel Technology Advanced Diesel Technology Model: E90 (335d) and E70 (XDrive35d) Production: From September 2008 After completion of this module you will be able to: • Locate diesel related components • Understand diesel emission control systems • Understand Digital Diesel Electronics (DDE) Perform diesel engine and engine management diagnosis Advanced Diesel Technology Introduction U.S. Market Diesel Introduction Beginning with model year 2009, BMW will introduce 2 diesel models for the first time since 1987. The E90 and E70 will be available with the new M57D30T2 (US) engine. The two new models will meet the EPA Tier 2, Bin 5 reguirements and will be considered “50 State” legal. In order to comply with these new stringent regulations, both vehicles have the latest in emission control and engine management technology. Both vehicles will be eguipped with the latest Selective Catalytic Reduction system to reduce unwanted NO x emissions. Also, the X5 will have an additional Low Pressure EGR system to further assist in the reduction of NO x . The E90 will be known as the 335d, while the E70 will reflect the new naming strategy as the X5 “Xdrive35d”. In addition to having a new engine, the new diesel powered 3-series will also be considered a “face-lifted” version (or LCI) with other changes to be detailed in future training. The newX5 Xdrive35d and 335d will be available in the late fall of 2008 with the same impressive six-cylinder diesel engine. The provisional fuel economy data is as follows: • 23/36 mpg (city/hwy) for the 335d • 19/26 mpg (city/hwy) for the X5 (X Drive 35d) Note: The above fuel economy data is provisional. The official EPA data is not currently available Advanced Diesel Technology 9 10 Advanced Diesel Technology A Diesel Engine for North America Impressive power and performance as well as exemplary efficiency have contributed to making BMW diesel engines an attractive as well as future-oriented drive technology. This technology is now being made available to drivers in North America. BMW is introducing this diesel technology to the USA and Canada under the name "BMW Advanced Diesel with Blue Performance". The introduction is an integral part of the Efficient Dynamics development strategy, which has become a synonym for extremely low CO 2 emissions - not surprising when considering its extremely low fuel consumption. Efficient Dynamics is not solely an instrument for reducing fuel consumption, but rather it is designed as an intelligent entity with increased dynamics. Not without good reason, the M57D30T2 engine is referred to as the world's most agile diesel engine. In the 2008 International Engine of the Year Awards, the BMW diesel came in second in the 2.5 to 3.0 liter category. Surprisingly, the M57D30T2 engine finished second only to the gasoline powered N54 engine. But, both the N54 and M57 diesel engines finished well ahead of the competition which included diesel engines from other manu¬ facturers. The following pages contain a comparison of the new BMW diesel engine technology to the current BMW gasoline engine technology. Technical Data Comparison Description Units of Measurement N52B3O01 N54B3000 N62B4801 M57D30T2 (US) Engine type R6 R6 V-8 R6 Displacement (cm3) 2996 2979 4799 2993 Firing order 1-5-3-6-2-4 1-5-3-6-2-4 1-5-4-8-6-3-7-2 1-5-3-6-2-4 Stroke mm 88 88.9 88.3 90 Bore mm 85 84 93 84 Power output @ rpm hp @ rpm 260@6600 300 @ 5800 360 @ 6300 265 @ 4200 Torque @ rpm Nm @ rpm 305@2500 400 @ 1300-5000 475 @ 3500 580@1750 Maximum engine speed rpm 7000 7000 6500 4800 Power output per liter hp/liter 86.7 100 75 89.3 Compression ratio ratio 10.7 : 1 10.2 : 1 10.5 : 1 16.5 : 1 Cylinder spacing mm 91 91 98 91 Valves/cylinder 4 4 4 4 Intake valve mm 34.2 31.4 35 27.4 Exhaust valve mm 29 28 29 25.9 Main bearing journal diameter mm 56 56 70 60 Connecting rod journal diameter mm 50 50 54 45 Fuel specification (Octane) (RON) 91-98 91-98 91-98 Diesel (Cetane 51) Engine management MSV80 MSD80 ME 9.2.2 DDE 7.3 Emission standard ULEV II ULEV II ULEV II ULEV II Advanced Diesel Technology 11 Power Output Comparison 12 Advanced Diesel Technology Diesel vs. N52 M57D30T2 (335d, X5 XDrive35d) N52B30O1 (X5 3. Osi) Diesel vs. N54 The following full load diagrams provide a comparison of the new diesel engine to the current production gasoline engines, both 6 and 8 cylinder. Most notably, the diesel has the advantage in the torgue output. The above comparison shows a comparison between the N52 engine, which is a naturally aspirated 3-liter gasoline engine. The power developed by the gasoline engine is carried over a broader RPM range, but the diesel has more output torgue which is available at a much lower engine speed. In the above graph, the N54 has a slight advantage in peak output with regard to horsepower. Since the N54 is a turbocharged engine, the output torgue figures show the torgue output at a lower engine speed, but it is guite “flat” up to almost 5000 RPM. In contrast, the diesel has a much higher torgue output, but is only available for a short time. After about 2400 RPM, the torgue drops off considerably. Comparison to the V8 Engine M57D30T2 (335d, X5 XDrive35d) N62B4801 (X5 4.8i) The familiar N62B4801 has impressive horsepower output but, even with 8-cylinders, it does not have the torque output of the M57 diesel engine. Overall, these engine output graphs illustrate that the diesel has very specific characteristics especially with regard to torque output. Vehicles with diesel engines are adapted to suit these torque characteristics with an upgraded torque converter and a rear axle gear ratio which allows the full utilization of the output curve. In short, the new BMW diesel engine exceeds all of the currently available gasoline engines up to an engine speed of about 4000 rpm. Advanced Diesel Technology 13 14 Advanced Diesel Technology Workshop Exercise - Vehicle Walkaround 1. Locate the following components on both vehicles (E70 and E90), look over both vehicles and fill in requested information: □ Locate the dipstick on the E70 and E90. Why is one red and one black? □ □ Look at the method of oil checking between both vehicles □ What is the difference between the two? □ _ □ - □ □ □ Locate the SCR fill points on both vehicles □ Where are they located? E70: _ E90: _ -- □ □ Locate the additional underbody paneling on the E90 Locate SCR reservoirs (tanks) on both vehicle and note locations: E70: Passive Tank_ Active Tank E90: Passive Tank _ Active Tank Locate the fuel filter Locate the oil filter and drain plug locations Locate the air filters and housings Open the fuel filler door and remove cap, note differences Examine the DPF on both vehicles and note the differences Note the EGR system and the differences between E70 and E90 Note the external appearance of the E70 and compare with gasoline version: How can you ID a diesel vehicle (without looking at the badges)? Note the external appearance of the E90 and compare with gasoline version: How can you ID a diesel vehicle (without looking at the badges)? Advanced Diesel Technology 15 16 Advanced Diesel Technology Engine Mechanical Engine Mechanical Changes For the US market, several changes were incorporated into the M57 engine. Some of the components affected include: • Bearings (crankshaft and connecting rod) • Pistons • Crankcase • Crankcase ventilation Bearings The connecting rod bearings are now lead-free. The familiar sputter bearing arrangement is still used. The upper (con rod side) bearing is a 3-layer sputter bearing. The cap side is a 2-layer non-sputter bear¬ ing. The crankshaft main bearings are still the conventional 3-layer (lead- based) bearings. Future engine designs will use completely “lead-free” bearings. Pistons The piston pin has a greater offset than in the European version. The offset of the piston pin means that the piston pin is slightly off center. This provides acoustic advantages during changes in piston contact. The acoustic advantages of increasing the offset are further developed particularly at idle speed. Crankcase In contrast to the European version, the M57D30T2 US engine has a larger reinforcement panel on the underside of the crankcase. The reinforcement panel now covers four of the main bearing blocks for the crankshaft. In principle, the reinforcement panel serves to enhance the stability of the crankcase. Note: Never drive the vehicle without the reinforcement panel. However, the enlargement was realized solely for acoustic reasons. Crankcase Vent The crankcase vent in the US version is heated. In addition, the operation of the crankcase breather is OBD monitored. This is because a leaking system would increase unwanted emissions. © © ® © © The only probable reason for a leak in the system would be that the blow-by pipe is not connected to the cylinder head cover. In order to facilitate protection of this situation by the OBD, the heating line is routed via a connector to the cylinder head cover (2). Essentially, this connector serves only as a bridge so that actuation of the heating system is looped through. The plug connection is designed in such a way that correct contact is made only when the blow-by pipe has been connected correctly to the cylinder head cover, i.e. the contact for the heating system is not closed if the blow-by pipe is not connected to the cylinder head cover. The OBD system recognizes this situation as a fault. Note: If the blow-by pipe is not connected to the cylinder head correctly, the OBD will activate the MIL (Malfunction Indicator Lamp). Note: When making repairs which concern malfunctions of the crankcase ventilation system. Or, if any repairs are made to a turbocharger which has leaked oil into the engine, be sure to remove any residual oil in the intake air system. Failure to do so may result in an engine over-rev situation causing irreparable engine damage. In this case, the warranty may be affected. Index Explanation Index Explanation 1 Cylinder head cover 5 Filtered intake air 2 Blow-by heater connection (OBD) 6 Blow-by heater connection at blow- by pipe 3 Blow-by heater connection at wiring harness 7 Intake air to exhaust turbocharger 4 Filtered air pipe 8 Blow-by pipe Advanced Diesel Technology 17 18 Advanced Diesel Technology Summary of Changes for the M57D30T2 (US) The following table provides an overview of the special features of the M57D30T2 US engine. They are divided into various categories. • New development signifies a technology that has not previously been used on BMW engines. • Modification signifies a component that was specifically designed for the M57D30T2 US engine but does not represent a technical innovation. • Adopted describes a component that has already been used in other BMW engines. This information describes only the main modifications to the M57D30T2 engine compared to the European version as well as funda¬ mental vehicle systems specific to diesel engines. Component/System New Development Modification Adopted Remarks Engine mechanical systems X Very few modifications have been made to the basic engine. The modifications that have been made focus mainly on ensuring smooth engine operation. A significant feature, however, is the OBD monitoring of the crankcase breather. Air intake and exhaust systems X The most extensive changes were made to the air intake and exhaust system. For instance, low pressure exhaust gas recirculation (low pressure EGR) is used for the first time at BMW on the E70. In addition to other minor adaptations, there are substantial differences in the sensor and actuator systems. Cooling system X In principle, the cooling system corresponds to that of the European versions, however, it has been adapted to hot climate requirements. Component/System New Development Modification Adopted Remarks High pressure fuel system X The functional principle of the fuel preparation system does not differ from that of the European version, however, individual components have been adapted to the different fuel specification. Fuel supply system X The fuel supply system is vehicle-specific and corresponds to the European version. There are, however, significant differences to petrol engine vehicles. Selective Catalytic Reduction System (SCR) X The SCR system is used for the first time at BMW. Nitrogen oxide emissions are drastically reduced by the use of a reducing agent that is injected into the exhaust system upstream of a special SCR catalytic converter. Since the reducing agent is carried in the vehicle, a supply facility, made up of two reservoirs, is part of this system Engine electrical system X The engine is equipped with the new DDE7 (digital diesel electronics) control unit that will be used in the next generation diesel engines (N57). The preheater (glow plug) system also corresponds to the N57 engines. Automatic transmission X The automatic transmission corresponds to that in the ECE variant of the X5 xDrive35d. The gearbox itself has already been used in the US version of theX5 4.8i, however, a different torque converter is used for the diesel model. Advanced Diesel Technology 19 20 Advanced Diesel Technology Vehicle Specific Diesel Changes Diesel Vehicles for the US Market Aside from the engine itself, there are several changes which have been made to the diesel versions of the 335d and X5. These changes are reguired to successfully adapt the diesel engine. These changes are as follows: • Transmission • Rear differential • Cooling system • Climate control system (auxiliary PTC heater) • Acoustic package Transmission In view of the high torgue developed by the M57D30T2 engine, the GA6HP26TU gearbox is used, which is normally fitted behind 8-cylinder gasoline engines. The transmission gear ratios have not been changed. Twin Damper Torque Converter The gearbox is identical to that used in the X5 4.8i; only the torgue converter is different. A so-called turbine torsional damper (TTD) is used while a twin damper torgue converter is used for diesel engines. In principle, the twin damper torgue converter is a turbine torsional damper with a further damper connected upstream. The primary side of the first damper is connected to the converter lockup clutch while the secondary side is connected to the primary side of the second damper. As in the turbine torsional damper, the secondary side is fixed to the turbine wheel of the torgue converter. When the converter lockup clutch is open, the power flow is egual to that of the turbine torsional damper. The power is transferred from the turbine wheel via the second damper (but without damp¬ ing) to the transmission input shaft. When the converter lockup clutch is closed, the power is transmit¬ ted via the first damper that consists of an annular spring. From here the power is transmitted to the second damper which operationally corresponds to the turbine torsional damper and also consists of two annular springs. These further improved damping properties effectively adapt the transmission to the operational irregularities of the diesel engine. Index Explanation Index Explanation 1 Annular spring 5 Stator 2 Converter housing 6 Transmission input shaft 3 Turbine wheel 7 Annular spring assembly 4 Impeller Rear Differential In order to optimize the torque curve of the diesel engine, the differential ratio has been changed in the final drive. The ratio is now numerically lower which keep the RPM to an optimum level. The following charts show the comparisons of the transmission and final drive ratios between the gasoline and diesel versions. Advanced Diesel Technology 21 22 Advanced Diesel Technology Cooling System The cooling system, is in part, vehicle-specific. In principle, there are scarcely any differences between the cooling systems on petrol and diesel engines. The two basic differences compared to a gasoline engine are: • No characteristic map thermostat • Addition of EGR cooler (LP and HP EGR). The E70 and E90 differ with regard to the EGR cooler. Since the E70 is eguipped with a low pressure EGR system, it has a second EGR cooler, the low pressure EGR cooler. Cooling System Overview - E90 Diesel Index Explanation Index Explanation 1 Transmission cooler (coolant to air) 9 Heater core (heat exchanger) 2 Radiator (coolant to air) 10 Water valve (dual) 3 Auxiliary radiator 11 Auxiliary coolant pump 4 Thermostat, transmission cooler 12 Engine oil cooler and engine oil to coolant heat exchanger 5 High pressure EGR cooler 13 Expansion tank 6 Thermostat 14 Transmission oil cooler and transmission oil to coolant heat exchanger 7 Coolant pump 15 Ventilation line 8 Coolant temperature sensor 16 Electric fan Cooling System Overview - E70 Diesel Index Explanation Index Explanation 1 Radiator (coolant to air) 10 Heater core (heat exchanger) 2 Transmission cooler (coolant to air) 11 Water valve (dual) 3 Electric fan 12 Auxiliary coolant pump 4 Thermostat, transmission cooler 13 Engine oil cooler and engine oil to coolant heat exchanger 5 High pressure EGR cooler 14 Expansion tank 6 Thermostat 15 Transmission oil cooler and transmission oil to coolant heat exchanger 7 Coolant pump 16 Ventilation line 8 Low pressure EGR cooler 17 Auxiliary radiator 9 Coolant temperature sensor Cooling Method The cylinder head varies according to the engineering used to implement the cooling concept. There are 3 types of cooling concepts: • Crossflow cooling • Longitudinal flow cooling • Combination of the two. In BMW diesel engines only crossflow cooling is used. With cross- flow cooling, the coolant flows from the hot exhaust side of the cylinder head to the cooler inlet side. This offers the advantage of even heat distribution throughout the cylinder head. By contrast, with longitudinal flow cooling, the coolant flows lengthways along the cylinder head, in other words from one end to the other. As the coolant flows past each cylinder in succession, it becomes progressively hotter, resulting in very uneven heat distribution. This also causes pressure losses in the coolant circulation system. A combination of both systems cannot outweigh the disadvantages of longitudinal flow cooling. Conseguently, BMW diesel engines exclusively use crossflow cylinder head cooling. Advanced Diesel Technology 23 24 Advanced Diesel Technology Climate Control for Diesel Vehicles The climate control system on the diesel vehicles is mostly identi¬ cal to those on vehicles with gasoline engines. The major addition to the system is an electric auxiliary PTC heater. Both the E70 and E90 use an auxiliary PTC heater. Since diesel engines are more thermally efficient than gasoline engines, the warmup time is increased. This can potentially cause a “comfort” related issue for the customer. So, this heater is need¬ ed to “boost” the output of the heater core until the coolant temperature is sufficient to provide the necessary heating. The PTC heater does not heat the coolant, but rather the air pass¬ ing through the heater core. The electric auxiliary heater is installed in the IHKA housing next to the heater core. This is connected to the IHKA via the LIN bus and is controlled between 0 - 100% when heating is required (infinitely variable). The electric PTC auxiliary heater may only be operated using excess alternator power. The power consumption can be limited via the DDE using power management. Notification of power availability is provided by the DDE via a CAN signal on the vehicle circuit and relayed to the electric PTC auxiliary heater by the IHKA via the LIN bus. The output of the electric PTC auxiliary heater is 1250 W at a voltage of 13 V. The electric auxiliary heater consists of a heating grid and integrated actuation electronics. The PTC heater has the following characteristics: • Ceramic heating elements (PTC ceramic resistors) • Access to air via metal grilles • Actuation electronics. Auxiliary PTC heater in A/C housing - E70 Index Explanation Index Explanation 1 IHKA housing 6 Evaporator temperature sensor 2 Fresh air intake 7 Heat exchanger 3 Connection to expansion valve 8 PTC heater 4 Coolant connection to heat exchanger (heater core) 9 Temperature sensor for heat exchanger 5 Evaporator Front PTC Pin Assignments The power connection and the signal connection are separate. Power connection: • Terminal 30 • Terminal 31. Front PTC signal connection: • Plug (3-pin) • Terminal 15 • Generator load signal (PWM) • LIN bus. The electric PTC auxiliary heater has diagnostic capability for detecting faults such as: • Missing contact • Short circuit to ground and B+ The electronic system performs continuous self-diagnosis. This makes it possible to activate internal safety functions and make the diagnostic data available to the IHKA control unit via the LIN bus. The following items have diagnostic capability: • Presence of power supply, terminal 15 and power supply voltage measurement • Power output stage fault The following safety functions are provided with the aid of self-diagnosis: • PTC shut-off if the permitted operating voltage range is exceeded. PTC Heater E90 Index Explanation Index Explanation 1 DDE 5 IHKA control module 2 Alternator 6 Instrument cluster 3 PTC heater (with integrated electronics) 7 Junction box 4 Ambient temperature Advanced Diesel Technology 25 26 Advanced Diesel Technology Acoustic Package On the E90, there is additional paneling in the underbody below the engine. This paneling is used to further reduce any engine related noise which may emanate from the diesel engine. Advanced Diesel Technology 27 28 Advanced Diesel Technology Diesel Engine Management In contrast to the ECE version of the M57D30T2 engine, the US version of the engine electrical system features following differences: • Engine control unit DDE7.3 • Preheating system with LIN-bus link and ceramic heater plugs • Additional OBD sensors • Electrically operated swirl flap and EGR valve • Additional actuators and sensors for the low pressure EGR system. Engine Control Module The new DDE7.3 engine control module is used on the US version M57D30T2 engine. The DDE 7 version is used due to the fact that the DDE 6 engine control module was not sufficient to accommodate the addition of the SCR system as well as addi¬ tional OBD functions. DDE 7 will be used on future generations of diesel engines including the N57 which will be available sometime later. Sensors and Actuators In the M57D30T2 US engine, the modifications to the sensors and actuators are restricted to the air intake and exhaust system. Several new components have been added to this system. The table below provides an overview. It shows a comparison between the E70 US and E90 US and the ECE variant (EUR04). EL Electrically actuated EUV Vacuum controlled via electric changeover valve (on/off) EPDW Vacuum controlled via electro-pneumatic pressure converter (PWM controlled) Sensors EURO 4 E70 US E90 US Outside temperature sensor X X X Ambient pressure sensor X X X HFM X X X Intake air temp sensor (in HFM) X X X Charge air temperature sensor X X X Boost pressure sensor X X X Exhaust pressure sensor at exhaust manifold (before DPF) X X X Oxygen sensor X X X Exhaust gas temperature sensor before diesel oxidation catalyst (DOC) X X X Exhaust gas temperature sensor before diesel particulate filter (DPF) X X X Exhaust backpressure sensor before diesel particulate filter (DPF) X - - Exhaust differential pressure sensor - X X Temperature sensor after LP-EGR cooler - X - Temperature sensor after HP-EGR cooler - X X Exhaust gas temperature sensor before SCR catalyst - X X Sensors EURO 4 E70 US E90 US NO x sensor before SCR catalyst - X X NO x sensor after SCR catalyst - X X Positional feedback swirl flaps - X X Positional feedback HP-EGR valve - X X Positional feedback LP-EGR valve - X - Blow-by connection - X X Actuators EURO 4 E70 US E90 US Compressor bypass valve EUV EUV EUV Turbine control valve EPDW EPDW EPDW Wastegate EPDW EPDW EPDW Throttle valve EL EL EL Swirl flaps EUV EL EL High pressure EGR valve EPDW EL EL Low pressure EGR valve - EPDW - Bypass valve for HP-EGR cooler - EUV EUV SCR metering valve EL EL Advanced Diesel Technology 29 30 Advanced Diesel Technology OBD Monitored Functions The engine management has the additional task of monitoring all exhaust-relevant systems to ensure they are functioning correctly. This task is known as On Board Diagnosis (OBD). The malfunction indicator lamp (MIL) is activated if the onboard diagnosis registers a fault. The events specific to US diesel engines that cause the MIL to light up are described in the following. Diesel Oxidation Catalyst The oxidation catalytic converter is monitored with regard to its conversion ability which diminishes with aging. The conversion of hydrocarbons (HC) during cold start is used as the indicator as heat is produced as part of the chemical reaction and it follows a defined temperature progression after the oxidation catalytic converter. The exhaust gas temperature sensor after the oxidation catalytic converter measures the temperature. The DDE maps the tempera¬ ture progression during cold start and compares it to calculated models. The result determines how effective the oxidation catalytic converter is operating. A reversible fault is stored if the temperature progression drops below a predetermined value. If this fault is still determined after two successive diesel particulate filter regeneration cycles, an irreversible fault is stored and the MIL is activated. SCR Catalytic Converter The effectiveness of the SCR catalytic converter is monitored by the two NO x sensors. The nitrogen mass is measured before and after the SCR catalytic converter and a sum is formed over a defined period of time. The actual reduction is compared with a calculated value that is stored in the DDE. The following conditions must be met for this purpose: • NO x sensors plausible • Metering active • Ambient temperature in defined range • Ambient pressure in defined range • Regeneration of diesel particulate filter not active • SCR catalytic converter temperature in defined range (is calculated by means of exhaust temperature sensor before SCR catalytic converter) • Flow of exhaust gas in defined range. Monitoring involves four measuring cycles. A reversible fault is stored if the actual value is lower than the calculated value. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activated. Long-term adaptation is implemented, where the metered quantity of urea-water solution is adapted, to ensure the effectiveness of the SCR catalytic converter over a long period of time. To execute this adaptation procedure, the signal of the NO x sensor after the SCR catalytic converter is compared with a calculated value. If variations occur, the metered quantity is correspondingly adapted in the short term. The adaptations are evaluated and a correction factor is applied to the metered quantity. The operating range for the long-term adaptation is the same as that for effectiveness monitoring. A reversible fault is stored if the correction factor exceeds a defined threshold. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activated. Supplying Urea-water Solution A supply of a urea-water solution is required to ensure efficient operation of the SCR catalytic converter. Once the SCR catalytic converter has reached a certain tempera¬ ture (calculated by the exhaust gas temperature sensor before the SCR catalytic converter), the metering control system attempts to build up pressure in the metering line. For this purpose, the metering module must be closed and the delivery pump actuated at a certain speed for a defined period of time. If the defined pressure threshold cannot be reached within a certain time, the metering module is opened in order to vent the metering line. This is followed by a new attempt to build up pressure. A reversible fault is stored if a defined number of pressure build-up attempts remain unsuccessful. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activated. This monitoring takes place only once per driving cycle before metering begins. Continuous pressure monitoring begins after this monitoring run was successful. A constant pressure of the urea-water solution (5 bar) is required for the selective catalytic reduction process. The actual pressure is measured by the pressure sensor in the delivery module and compared with a minimum and a maximum pressure threshold. A reversible fault is stored if the limits are exceeded for a certain time. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activated. This monitoring run takes place while metering is active. Level Measurement in Active Reservoir A level sensor with three contacts at different heights is used for the active reservoir. The plausibility of the sensor is checked in the evaluator in that it checks whether the signals are logical. For example, it is improbable that the "Full" contact is covered by the solution while the "Empty" contact is not. In this case, the evaluator sends a plausibility error to the DDE. This takes place at a pulse duty factor of 30% of the PWM signal. A reversible fault is set. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activated. This monitoring procedure only takes place if the temperature in the active reservoir is above a defined value. If the line between the evaluator and at least one contact of the level sensor is interrupted, the fault is signalled to the DDE by a PWM signal with 40% pulse duty factor. A reversible fault is set. If the fault is determined in two successive driving cycles, an irre¬ versible fault is stored and the MIL is activated. Suitable Urea-water Solution The SCR system is monitored with regard to refilling with an incor¬ rect medium. This monitoring function starts when refilling is detected. Refilling detection is described in the section on the SCR system. Effectiveness monitoring of the SCR catalytic converter is used for the purpose of determining whether an incorrect medium has been used. An incorrect medium is detected if the effectiveness drops below a certain value within a defined period of time after refilling. A reversible fault is set in this case. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activated. In addition, the warning scenario with a remaining range of 200 mis is started. Advanced Diesel Technology 31 32 Advanced Diesel Technology NO x Sensors A dew point must be reached for effective operation and therefore also the monitoring of the NO x sensor. This ensures that there is no longer any water in the exhaust system that could damage the NO x sensors. A reversible fault is set if the following monitoring functions detect a fault at the NO x sensor. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activat¬ ed. • Detection signal or correction factor incorrect • Line break or short-circuit between measuring probe and con¬ trol unit of NO x sensor • Measured value outside the defined range for a certain period of time • Operating temperature is not reached after a defined heating time • The distance from the measured value to zero is too great in overrun mode (no nitrogen oxides expected) • During the transition from load to overrun mode, the signal of the NO x sensor does not drop fast enough from 80% to 50% (only NO x sensor before SCR catalytic converter) Exhaust Gas Recirculation (EGR) During normal operation, the exhaust gas recirculation is controlled based on the EGR ratio. During regeneration of the diesel particu¬ late filter, it is conventionally controlled based on the air mass. The monitoring function also differs in this way: During normal operation a fault is detected when the EGR ratio is above or below defined limits fora certain period of time. This applies to the air mass during regeneration of the diesel par¬ ticulate filter. In order to monitor the high pressure EGR cooler, the temperature after the high pressure EGR cooler is measured with the bypass valve open and close with the engine running at idle speed. A fault is detected if the temperature difference is below a certain value. For the low pressure EGR cooler (only E70), the measured temper¬ ature after the low pressure EGR cooler is compared with a calcu¬ late temperature for this position. A fault is detected if the differ¬ ence exceeds a certain value. Each of these faults is stored reversible. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activated. • If, despite a peak in the signal of the NO x sensor before the SCR catalytic converter, at least a defined change in the signal of the NO x sensor after the SCR catalytic converter is not determined this is interpreted as implausible. Diesel Particulate Filter (DPF) The diesel particulate filter is monitored by means of the differential pressure sensor. If the filter is defective, the differential pressure before and after the filter will be lower than for a new filter. Monitoring starts when the flow of exhaust gas and the diesel particulate filter temperature exceed certain values. A fault is detected when the differential pressure drops below a defined threshold fora certain period of time. Conversely, an overloaded/clogged diesel particulate filter is detect¬ ed when the differential pressure exceeds a defined value for a certain period of time. When regeneration of the diesel particulate filter is started, the time required until the exhaust temperature before the DPF reaches 250°C is measured. This time is set to zero if the engine runs for a longer period of time at idle speed or in overrun mode. A fault is detected if a defined time is exceeded before the temperature of 250°C is reached. In this way, the response characteristics of the increase in exhaust temperature for DPF regeneration are monitored. The system also monitors whether the exhaust gas temperature before the diesel particulate filter corresponds to the expected value after a defined period of time. If this is not the case although the control system has reached its limits, a fault is detected. Also in this case, each of these faults is stored reversible. If the fault is determined in two successive driving cycles, an irreversible fault is stored and the MIL is activated. Advanced Diesel Technology 33 34 Advanced Diesel Technology Air Intake and Exhaust Systems The M57D30T2 US engine exhibits the following special features in the air intake and exhaust system: • Electric swirl flaps • Electric exhaust gas recirculation valve (High pressure EGR valve) • Low pressure EGR (E70 only) • Turbo assembly adapted for low pressure EGR. (E70 only) Index Explanation Index Explanation 1 Diesel engine - M57D30T2 18 Oxidation catalyst and Diesel particle filter (DOC/DPF) 2 Intake silencer (air filter) 19 Exhaust gas temperature sensor - pre catalyst (DOC) 3 HFM 20 Oxygen sensor 4 Compressor bypass valve 21 Wastegate valve 5 Turbocharger - low pressure stage 22 Turbine control valve 6 Turbocharger - high pressure stage 23 Exhaust pressure sensor (after exhaust manifold) 7 Bypass valve for High Pressure EGR cooler 24 Swirl port actuator 8 High-pressure EGR cooler 25 Boost pressure sensor 9 Temperature sensor for high-pressure EGR 26 Exhaust differential pressure sensor 10 High-pressure EGR valve 27 NO x sensor - pre SCR catalyst 11 Throttle valve 28 Temperature sensor - post DPF 12 Charge air temperature sensor 29 Dosing (metering) module (for SCR system) 13 Intercooler 30 Mixer (for SCR system) 14 Low pressure EGR valve with position sensor 31 SCR Catalyst 15 Temperature sensor for low pressure EGR 32 NO x sensor - post SCR catalyst 16 Low pressure EGR cooler 33 DDE 7.3 17 Exhaust gas temperature sensor - post catalyst (DOC) 34 Muffler (silencer) Advanced Diesel Technology 35 36 Advanced Diesel Technology Air Intake Systems The intake air ductwork differs between the E70 and E90. Both vehicles will draw air from behind the kidney grill. On the E70, the air filter housing and silencer is located on top of the engine. On the other hand, the E90 has a filter housing on the passenger side inner fender. Index Explanation Index Explanation A Air intake system - E70 3 Air filter housing B Air intake system - E90 4 HFM 1 Intake air point of entry 5 Fresh (filtered) air intake pipe 2 Unfiltered air intake 6 Blow-by tube Swirl Flaps The US version of the M57 engine utilizes the previously known swirl flaps which are located in the intake manifold. The primary differ¬ ence is that the swirl flaps are now controlled electrically, rather than with vacuum. This method of actuation also provides a means of position feedback with the DDE system to comply with OBD requirements. An additional benefit of this method of control is a more precise positioning of the swirl flaps as needed. The flaps are map controlled using engine speed, engine load and coolant temperature. © © ® ® @© © Index Explanation Index Explanation 1 Control rod for swirl flaps 5 Swirl ports 2 Throttle plate mounting 6 Tangential ports 3 Intake manifold 7 Swirl flaps 4 Electric motor (for swirl flaps) Advanced Diesel Technology 37 38 Advanced Diesel Technology Exhaust System The exhaust systems for both the E90 and E70 have been adapted for the US market. There are special provisions for the SCR system as well as for the US specific OBD monitoring of the DOC. Each system is unique to the vehicle with different muffler and tailpipe features. Index Explanation Index Explanation A Exhaust system E70 6 SCR catalyst B Exhaust system E90 7 NO x sensor after SCR catalyst 1 Oxygen sensor Exhaust gas temperature sensor before DOC (concealed) 8 Rear silencer (muffler) 2 Exhaust gas temperature sensor after DOC 9 Exhaust gas temperature sensor after DPF 3 Differential pressure sensor 10 Metering module 4 NO x sensor before SCR catalyst 11 Diesel particulate filter (DPF) 5 Mixer EGR System For more information on EGR systems, refer to the section on “Emission Controls”. Advanced Diesel Technology 39 40 Advanced Diesel Technology Workshop Exercise - Exhaust System Components 1. Complete exercise by filling in the ‘‘function/purpose” of the exhaust system components. Then, locate and identify the exhaust system components on the vehicle: Index Explanation Function/Purpose A Exhaust system E70 E70 B Exhaust system E90 E90 1 Oxygen sensor Exhaust gas temperature sensor before DOC (concealed) 2 Exhaust gas temperature sensor after DOC 3 Differential pressure sensor 4 NO x sensor before SCR catalyst 5 Mixer 6 SCR catalyst 7 NO x sensor after SCR catalyst 8 Rear silencer (muffler) 9 Exhaust gas temperature sensor after DPF 10 Metering module 11 Diesel particulate filter (DPF) Workshop Exercise - Exhaust System Components _ Using the diagnostic equipment, access the “Service Functions” menu and go to DPF. (Do not start vehicle at this time) What are the two selections in the DPF menu? According to the test module, what is the replacement interval of the DPF? When should the “DPF Regeneration” test module be carried out? Flow is the “DPF Regeneration” test module carried out? (i.e. Can it be completed in the shop?) Go to “Status Requests” under the DPF section and highlight all values. Read out with the engine running. Fill in chart below with the values: Status request Value Status request Value Differential pressure sensor Consumption per 100km Regeneration enabled Distance remaining on DPF Regeneration released Distance traveled since regeneration Advanced Diesel Technology 41 42 Advanced Diesel Technology | Classroom Exercise - Review Questions 1. What changes were made to the piston on the US version of the M57D30T2 engine? (circle one) The piston pin is larger in diameter The piston pin is offset in the piston The piston pin is made from a stronger material The piston pin is lighter 2. Which of the following statements are TRUE regarding the driveline changes on the diesel vehicles? (circle the true statements, cross out the false statements) On the diesel vehicles, the gear ratio in the differential is the same as the gasoline powered vehicles. The transmission gear ratios are the same The transmission on the diesel vehicles is also used on the 8-cylinder, gasoline powered vehicles The torgue converter is the same between gasoline and diesel powered vehicles 3. Why is it important to be sure that the air intake system is “oil-free” before starting the engine? 4. Which of the following engine management components are “electrically actuated” (directly connected) by the DDE? (circle those that apply) Compressor bypass valve SCR metering valve Bypass valve for HP-EGR cooler Wastegate Throttle valve Swirl flaps High pressure EGR valve Low pressure EGR valve Turbine control valve 5. Which of the following engine management components are “vacuum controlled” (via EPDW) by the DDE? (circle those that apply) Compressor bypass valve SCR metering valve Bypass valve for HP-EGR cooler Wastegate Throttle valve Swirl flaps High pressure EGR valve Low pressure EGR valve Turbine control valve Advanced Diesel Technology 43 44 Advanced Diesel Technology Fuel System Fuel Supply Overview As with current gasoline fuel injection systems, there is an electric fuel pump located in the fuel tank. The fuel pump supplies the needed low pressure fuel to feed the mechanical high-pressure pump. Index Explanation 1 Fuel filler neck 2 Left hand service opening 3 Fuel return line 4 Fuel filter with heating system 5 Right hand service opening 6 Filler vent 7 Electric fuel pump module (EKP) The fuel tank is eguipped with two chambers and, on modern vehicles, is made from plastic. The electric fuel pump on the diesel engines is driven by the EKP module. Similar to BMW gasoline engines, the fuel system on the vehicles eguipped with diesel engines share much of the same “low pres¬ sure” system components. However, there are some distinct differences with the diesel engine. These are: • The system includes a fuel return line • The breather system is significantly simpler • There is no carbon canister (AKF) and no fuel tank leakage diagnosis module (DMTL) • There is no pressure regulator • The fuel filter is not located in the fuel tank. The design layout of the fuel supply systems in the E70 and E90 are described in the following. Fuel Tank As with all modern BMW vehicles, the fuel tank is made from plastic and is installed in the optimum position to achieve the best possible weight balance in the vehicle. To accommodate these needs, the fuel tanks must be designed in such a way so that there is room for the driveshaft to pass through with out interference. So, the fuel tanks in the diesel vehicles feature the familiar “double¬ chamber” configuration. This design feature accommodates two delivery units which are located in the right and left fuel tank halves. The fuel pump (3) with intake filter (2) is a part of the right-hand delivery unit. The surge chamber including a suction jet pump (10) with pressure relief valve (11) and initial fill valve (1) as well as a lever-type sensor (G) complete this delivery unit. The suction jet pump (8), lever-type sensor (G), leak prevention valve (7) and air inlet valve (9) belong to the left-hand delivery unit. A line leads from the filler vent valve (H) to the filter (L). The fuel filler pipe is connected to this line via the non-return valve (K). E70 Fuel Tank Index Explanation Index Explanation A Fuel filler cap 1 Initial fill valve B Pressure relief valve 2 Intake mesh filter C Non-return valve 3 Fuel pump D Surge chamber 4 Pressure relief valve E Fuel tank 5 Feed line F Service cap 6 Return line G Lever-type sensor 7 Leak prevention valve H Filler vent valve 8 Suction jet pump 1 Connection 9 Air inlet valve J Maximum fill level 10 Suction jet pump K Non-return valve 11 Pressure relief valve L Filter Advanced Diesel Technology 45 46 Advanced Diesel Technology E90 Fuel Tank Index Explanation Index Explanation A Fuel filler cap 1 Initial fill valve B Pressure relief valve 2 Intake mesh filter C Non-return valve 3 Fuel pump D Surge chamber 4 Pressure relief valve E Fuel tank 5 Feed line F Service cap 6 Return line G Lever-type sensor 7 Leak prevention valve H Filler vent valve 8 Suction jet pump 1 Connection 9 Air inlet valve (check valve) J Maximum fill level 10 Suction jet pump L Filter 11 Pressure relief valve Fuel Tank Functions A pressure relief valve (B) is integrated in the fuel filler cap (A) to protect the fuel tank (E) from excess pressure. A non-return flap (C) is located at the end of the fuel filler neck. The non-return flap prevents the fuel from sloshing back into the fuel filler neck. The components in the fuel tank can be reached via the two service caps (F). The fuel fill level can be determined via the two lever-type sensors (G). The surge chamber (D) ensures that the fuel pump always has enough fuel available for delivery. Index Explanation Index Explanation A Fuel filler cap E Fuel tank B Pressure relief valve F Service cap C Non-return valve G Lever-type sensors D Surge chamber Fuel Delivery from Fuel Tank In the event of the surge chamber being completely empty, the initial filling valve (1) ensures that fuel enters the surge chamber while refuelling. The fuel reaches the fuel pump (3) via the intake filter (2), then continues through the delivery line (5) to the fuel filter. The fuel pump is located in the surge chamber. A pressure relief valve (4) is integrated in the fuel pump to prevent pressure in the delivery line from rising too high. Index Explanation Index Explanation 1 Initial fill valve 7 Leak prevention valve 2 Intake mesh filter 8 Suction jet pump 3 Fuel pump 9 Air inlet valve 4 Pressure relief valve 10 Suction jet pump 5 Feed line 11 Pressure relief valve 6 Return line As the engine switches off, the delivery line is depressurized but cannot run dry because, provided the system is not leaking, no air is able to enter it. In addition, after the fuel pump has switched off, the fuel pressure/temperature sensor is checked for plausibility. Fuel that is required for lubrication and the function of high pres¬ sure generation flows back into the fuel tank via the return line (7). The fuel coming from the return line is divided into two lines down¬ stream of the leak prevention valve (7). The non-return valve prevents the fuel tank from draining in the event of damage to lines on the engine or underbody. It also prevents the return line from running dry while the engine is off. One of the lines guides the fuel into the surge chamber via a suc¬ tion jet pump (10). The suction jet pump transports the fuel from the fuel tank into the surge chamber. If the fuel delivery pressure in the return line increases too much, the pressure relief valve (11) opens and allows the fuel to flow directly into the surge chamber. An air inlet valve is used in the E70. The air inlet valve (9) ensures that air can enter the line when the engine is off, preventing fuel from flowing back from the right-hand half of the fuel tank to the left. Instead of the air inlet valve (9) a non-return valve is used on the E90. The non-return valve ensures that, while the engine is off, fuel from the right-hand half of the fuel tank cannot flow back into the left-hand half. The return system remains completely filled with fuel. A further line branches off into the left-hand half of the fuel tank after the non-return valve (7) and transports the fuel into the surge chamber via the suction jet pump (8). Advanced Diesel Technology 47 48 Advanced Diesel Technology Air Supply and Extraction Fuel ventilation is ensured by means of the filler vent valve (H). The filler vent valve is located in the fuel tank and uses the connec¬ tion (I) to determine the maximum fill level (J). The filler vent valve contains a float that buoys upwards on the fuel when the vehicle is refuelled and blocks the filler ventilation. The fuel rises in the fuel filler and the fuel nozzle switches off. A roll-over valve is also integrated in the filler vent valve to block the ventilation line when a certain angle of incline is reached and prevents fuel from draining out if the vehicle were to roll over. The filter (L) prevents dirt or insects from entering the ventilation and blocking the line. If the ventilation line does become blocked, fuel consumption during operation would cause negative pressure and the fuel tank would be compressed and damaged. Fuel Filler Cap The fuel filler cap contains a pressure relief valve to ensure that, if there is a problem with fuel tank ventilation, any excess pressure that may form can escape and the fuel tank is not damaged. The non-return valve (K) prevents fuel from escaping via the venti¬ lation when the vehicle is refuelled. During operation, air can flow into the fuel filler pipe and the fuel can flow from the fuel filler pipe into the tank. Index Explanation Index Explanation H Filler vent valve K Non-return valve 1 Connection L Filter J Maximum fill level If excess pressure forms in the fuel tank, this causes the valve head (1) and with it the entire pressure relief valve (5) to be lifted off the sealed housing (6). The excess pressure can now escape into the atmosphere. The excess pressure spring (2) determines the opening pressure. The excess pressure spring uses a defined pressure to push the pressure relief valve onto the sealed housing and is supported by the brace (3). Index Explanation 1 Valve head 2 Excess spring pressure 3 Brace 4 Bottom section of housing 5 Pressure relief valve 6 Sealed housing Misfueling Protection A mechanical system has been developed in order to help prevent a mis-fueling situation. To make sure that the diesel vehicles are only refueled with the proper diesel fuel, a mechanical flap has been added to the fuel filler neck. As the following illustrations show, only a fuel nozzle with a diame¬ ter of approximately 24 mm can fit. If the diameter is approximately 21 mm, the flap (4) does not open as the hinged lever (7) and the locking lever (2) cannot be pushed apart. If a diesel fuel nozzle is inserted, this pushes the locking lever (2) and the hinged lever (7) at the same time. The hinged lever is pushed outwards against the tension spring (3) and releases the flap (4). This is only possible, however, if the hinged lever cannot move freely and is also locked in position by the fuel nozzle. To open the protection against incorrect refuelling feature in the workshop, a special tool is reguired. Index Explanation Index Explanation 1 Housing 5 Torsion spring 2 Locking lever 6 Rivet 3 Tension spring 7 Hinged lever 4 Flap 8 Ground strap Advanced Diesel Technology 49 50 Advanced Diesel Technology Fuel Pump Today's diesel vehicles are fitted with electric fuel pumps to deliver the needed fuel to the high pressure pump. The electric fuel pump is designed to deliver a sufficient amount of fuel to lubricate and cool the injectors and the high-pressure pump and to satisfy the maximum fuel consumption of the engine. It has to deliver the fuel at a defined pressure. That means that when the engine is idling or running at medium power, the fuel pump delivers several times more than the amount of fuel required. The fuel pump delivers approximately three or four times the volume of maximum possible fuel consumption. The electric fuel pump is located in the fuel tank. There it is well protected against corrosion and the pump noise is adequately soundproofed. The fuel pump on BMW diesel engines may either be a gear pump, a roller-cell pump or a screw-spindle pump. The following fuel pumps are used on USA vehicles: • E70 - Screw spindle pump • E90 - Gear pump (rotor type) The operating principle of each of these types of pump is described below. The pump itself is driven by the drive shaft (2) of the electric motor (3). The electric motor is controlled by the electrical connection (6) and sliding contacts (7). Passing first through the intake filter and then the remainder of the intake section (9), the fuel enters the impeller (1). The fuel is pumped through pressure chamber (8) on the electric motor, past the pressure connection (5) and onwards to the fuel filter and engine. If the fuel delivery pressure increases to an impermissible value, the pressure relief valve (4) opens and allows the fuel to flow into the surge chamber. Index Explanation Index Explanation 1 Impeller 6 Electrical connection 2 Driveshaft 7 Sliding contacts 3 Electric motor 8 Pressure chamber 4 Pressure relief valve 9 Intake section 5 Pressure connection Fuel Pump - E90 On the E90, the fuel pump is a gear type pump. The gear pump is comprised of an outer rotor (1) with teeth on the inside, and an inner rotor (4) with teeth on the outside. The inner rotor is driven by the drive shaft (5) of the electric motor. The outer rotor is pro¬ pelled by the teeth of the inner rotor and thus turns inside the pump housing. The inner rotor has one tooth fewer than the outer rotor, which means that, with each revolution, fuel is carried into the next tooth gap of the outer rotor. During the rotary motion, the spaces on the intake side enlarge, while those on the pressure side become proportionately smaller. The fuel is fed into the rotor pump through two grooves in the housing, one on the intake side and one on the pressure side. Together with the tooth gaps, these grooves form the intake section (6) and pressure section (3). Index Explanation 1 Outer rotor 2 Fuel delivery to engine 3 Pressure section 4 Inner rotor 5 Driveshaft 6 Intake section 7 Fuel from tank Screw-spindle Pump - E70 With the screw-spindle pump, two screw spindles intermesh in such a way that the flanks form a seal with each other and the housing. In the displacement chambers between the housing and the spindles, the fuel is pushed towards the pressure side with practically no pulsation. In this way, the screw spindles pump fuel away from the fuel tank (5). The fuel is then fed to the engine (3) through the pump housing and the fuel delivery line. Index Explanation 1 Driveshaft screw spindle 2 Gearwheel 3 Fuel delivery to the engine 4 Screw spindle 5 Fuel from tank 0 0 3 0 0 Advanced Diesel Technology 51 52 Advanced Diesel Technology Low Pressure Fuel System - E90 The low pressure fuel systems differ between the E70 and E90. The E90 is a “speed regulated” system which means that the fuel pump speed is regulated by the EKP module based on request from the DDE. The fuel pump will be activated with the “ignition on” signal. If the engine is not started, the fuel pump will be switched off after a defined time period. When the engine is switched off, the fuel pump is switched off as well. Fuel Temperature Sensor The fuel temperature sensor is Fuel temperature sensor - E90 located in the fuel feed line just before the high pressure pump. The sensor consists of a tem¬ perature dependent resistor with which works on the NTC principle. The fuel temperature sensor registers the fuel temperature just before the high pressure pump. The fuel temperature sen¬ sor is installed on the low pres¬ sure side of the fuel system. The density of the fuel changes as temperature changes. The DDE requires the fuel temperature for the purpose of precisely calculat¬ ing the start of injection and injection quantity. The fuel temperature sensor consists of a temperature-dependent measuring resistor made from semiconductor material that is inte¬ grated in a housing. The measuring resistor has a negative temperature coefficient (NTC). The digital diesel electronics compares the measured voltage with a characteristic curve that assigns a corresponding temperature to each voltage value. The various sensors and actuators are required for ensuring effective operation of the fuel system and engine. Apart from ensuring compliance with legal requirements, these components are also responsible for providing outstanding engine performance and the associated acoustics. Fuel Filter Heating - E90 On the E90, the fuel filter heater is not controlled directly by the DDE. A pressure switch and a temperature sensor are located in the fuel filter housing. The fuel heater only works with the ignition switched on and when both of the following conditions are fulfilled: • Temperature drops below a defined value • A defined fuel delivery pressure is exceeded due to cold, viscous fuel. If the filter is clogged, a corresponding signal is sent via a diagnosis line to the DDE. This is the case when, despite a sufficiently high temperature, the fuel pressure upstream of the filter does not drop. The conditions for fuel filter heater operation are as follows: • The fuel heater is is switched ON when - the fuel pressure is greater than 6 bar AND the fuel temperature is less than 2°C. • The fuel heater is switched off when - the fuel pressure is less than 5.5 bar for a duration of greater than 5 minutes OR • the fuel temperature is greater than 12°C OR • during the starting process if the electronics in the fuel filter detect a battery voltage of less than 7.5 V for longer than 0.2 seconds. The fuel heater is not activated by the DDE control module. However, the fuel heater reports a detected filter blockage via the signal DIAG_DKH to the DDE control module. The DDE control module then stores the fault. Advanced Diesel Technology 53 54 Advanced Diesel Technology Low Pressure Fuel System - E70 The low pressure fuel system on the E70 is a “pressure regulated” system which uses the signal from the fuel pressure sensor located in the low pressure fuel line. The fuel pump operates with "ignition ON". If the engine is not started, the fuel is switched off at a specific pressure. When the engine is running, the fuel pump is regulated on-demand by the EKP module in response to a load signal from the DDE in order to ensure a uniform fuel pressure at the inlet to the high-pressure pump. The functions of the low pressure fuel system are integrated into the DDE control module. The DDE uses the pressure information from the combined fuel pressure-temperature sensor to determine the current actual pressure in the low pressure system. In order to maintain the approximate delivery pressure of 4.8 to 5.0 bar, the DDE uses a number of input variables. The input variables relevant to determining the adjusting value are: • Actual pressure in the pre-supply system • Engine speed • Injection volume The adjusting value is sent from the DDE to the EKP module in the form of a CAN message. Fuel Pressure-temperature Sensor The fuel pressure-temperature sensor consists of two independent sensors combined in one housing. The fuel temperature sensor is reguired to precisely calculate the start of injection and injection quantity. The fuel pressure sensor registers the fuel pressure upstream of the high pressure pump. This fuel pressure is required for the purpose of controlling the fuel pump in the fuel tank. The fuel pump is also switched off when the engine is turned off and the fuel feed is depressurized. After the fuel pump has been shut down, the digital diesel electronics checks and evaluates the plausibility of the fuel pressure sensor. If a fault is detected, the corresponding fault code is stored in the fault code memory of the digital diesel electronics. The integrated fuel temperature sensor is identical to the fuel temperature sensor used in the E90. The fuel pressure sensor is also integrated in the housing. Both the fuel pressure sensor and the fuel temperature sensor features two separate connections in a common connector housing that has four pins. The fuel pressure sensor consists of resistors mounted on a diaphragm. The one side of the diaphragm has contact with the fuel so that the fuel pressure acts on the diaphragm. The greater the pressure, the more the diaphragm is deflected. The resistors on the diaphragm change their resistance in response to the mechanical stress. A bridge circuit and electronic signal processing circuitry in the sensor amplify the bridge voltage, compensate for temperature influences and linearize the pressure characteristic curve. The output voltage for the digital diesel electronics is in the range between 0 and 5 volts. As for the temperature sensor, a character¬ istic curve is stored in the digital diesel electronics that assigns a corresponding pressure to each voltage value. Fuel Filter Heating - E70 The fuel filter heating operation is somewhat different in the E70. The E70 has a pressure-controlled fuel supply system. In this sys¬ tem, the fuel filter heater is actuated by the DDE. The DDE com¬ municates with the filter heater via the signal S_KSH. A combined fuel pressure and temperature sensor upstream of the high pressure pump is used. If reguired, the fuel filter is heated with an electrical heating element. The DDE switches the fuel filter heating on under the following conditions: • Temperature drops below a defined value • The reguired fuel pressure is not reached despite increased power intake of the electric fuel pump. The DDE recognizes a clogged filter when the target pressure upstream of the high pressure pump is not reached despite a sufficiently high fuel temperature and high current consumption of the electric fuel pump. The electrical power output of the fuel pump is higher than the stored adaptation value ’’electric fuel pump” plus an offset for more than 3 seconds. The offset is determined from a characteristic map and depends on the engine speed and fuel injection rate. The fuel filter heating is switched off again under the following con¬ ditions: • Activation time > 5 min or • Fuel temperature > 8°C or • Battery voltage is less than 9 volts for more than 30 seconds Advanced Diesel Technology 55 56 Advanced Diesel Technology High Pressure Fuel System The high pressure fuel system is mostly identical in design and function as compared to the European version. However, some components have been adapted to the different fuel specification. These components are: • High-pressure pump • Fuel rail • Fuel injectors. These adaptations are restricted to different coatings and materials on the inside. Index Explanation Index Explanation A Fuel feed (low pressure) 6 Return line B Fuel return 7 Feed line C Fuel high pressure 8 Fuel temperature (or temp/pressure) 1 Fuel rail pressure sensor 9 High pressure line 2 High pressure line 10 Fuel rail 3 Leakage line 11 Restrictor 4 Piezo injector 12 High pressure pump 5 Fuel rail pressure control valve 13 Volume control valve Fuel Injectors Compared to a piezo fuel injector on a gasoline engine, the diesel injector operates guite differently. The concept of piezo electricity is the same, but applied in a different manner. On a gasoline engine, the piezo element is used to physically operate the injector pintle in an outward motion. Due to the very high pressures used in a diesel engine, the piezo element cannot be used to directly actuate the pintle. The pintle on a diesel fuel injector moves inward (away from the combustion chamber). Instead, the piezo element is used to trigger a relay valve in the actuator module. The injector is then hydraulically “imbalanced” which causes the pintle to open via the fuel rail pressure. The piezo-element (2) is located inside the actuator module (5). When controlled, it produces the movement necessary to open the relay valve. Circuited between the two elements is the coupler module (6), which functions as a hydraulic compensating element, e.g. to compensate for temperature-related length expansions. When the fuel injector is controlled, the actuator module expands. This movement is transferred to the relay valve (7) by the coupler module. When the relay valve opens, the pressure in the control chamber (1) drops and the nozzle needle opens. The benefits of the piezo-fuel injector are that they offer a consid¬ erably faster control response, which results in greater metering accuracy. In addition, the piezo-fuel injector is smaller, lighter and has a lower power consumption. Index Explanation Index Explanation 1 Control chamber 5 Actuator module 2 Piezo element 6 Coupler module 3 High pressure supply 7 Relay valve 4 Supply duct to the nozzle 8 Nozzle needle Advanced Diesel Technology 57 Piezo Injector Operation 58 Advanced Diesel Technology Index Explanation 1 Coupler module 2 Control valve 3 Bypass 4 Nozzle needle 5 Restrictor 6 Control volume 7 Outlet 8 Supply duct to nozzle Injector Opening If the fuel injector is activated by the DDE, the piezo-element presses the control valve (2) down against the spring force via the coupler module (1) and closes the bypass (3). The fuel from the control volume (6) can then flow across the outlet (7) and the control valve. The pressure in the control volume drops and the nozzle needle (4) is opened by the fuel delivery pressure. Injector Closing If the injector current feed is set by the DDE, the piezo-element contracts and the coupler module is pressed back by the spring force. The spring in the control valve closes the valve and clears the bypass. Fuel now reaches the control volume via the bypass, outlet (7) and restrictor (5) and presses the nozzle needle down. The injector is closed and injection is finished. Coupler Module The hydraulic coupler is surrounded by diesel fuel at a pressure of approximately 10 bar. The piezo-element acts on the upper plunger (1). Lower plunger (6) rests on control valve (9). The force of spring (7) and of spring (8) is set in such a way that, when closed, the piezo element and control valve (9) are connected free of play via the coupler module. The upper plunger (1) presses against coupler chamber (5) when the piezo-element is activated. The force of the piezo-element is increased since plunger (1) has a larger diameter than plunger (6). Plunger (6) opens the control valve (9). When the coupler chamber is pressurized during activa¬ tion, a small leakage guantity escapes via the clearance in the plunger guide into fuel return (2). Index Explanation A Fuel feed B High pressure fuel 1 Plunger 2 Fuel return 3 Spring 4 Coupler 5 Coupler chamber 6 Plunger 7 Spring 8 Spring 9 Control valve After injection or after the piezo-element has been switched off, the springs (7 and 8) balance out the play created by the leakage guan¬ tity and fuel is again drawn via the clearance in the piston guide into the coupler chamber. This balancing out process takes place so fast that the coupler chamber is completely filled again by the next injection cycle. A return pressure of approximately 10 bar is reguired for this purpose, which is achieved by the restrictor in the fuel return of the fuel injectors. The control valve is not operated and no fuel is injected when no pressure is applied in the fuel feed. Leakage Oil The piezo injectors reguire a certain amount of backpressure in the leakage circuit in order to operate properly. So, the leakage circuit on the 3rd generation common rail differs from the earlier versions. In past versions (such as 1st and 2nd generation common rail), the leakage oil circuit drained into the fuel return line. However, since the piezo injectors operate differently than the earlier solenoid valve injectors, the leakage circuit has been redesigned. A certain amount of leakage oil occurs in the diesel fuel injectors due to the design of the system. The reason for this is that the relay valve in the piezo-fuel injector needs a certain back pressure to work correctly. The relay valve requires about 10 bar to be pres¬ ent in the leakage circuit to prevent injector malfunctions. In order to maintain this pressure, a restrictor (11) has been installed between the injector(s) and the low pressure feed to the HP pump. Advanced Diesel Technology 59 60 Advanced Diesel Technology * A 1 _®_A ® Leakage oil circuit - M57 ■ B 3rd generation common rail Index Explanation Index Explanation A Fuel feed 5 High pressure pump B Fuel high pressure 6 Rail pressure control valve C Fuel return 7 Fuel rail 1 Fuel tank 8 Fuel pressure sensor 2 Fuel filter and filter heating 9 Piezo fuel injector 3 Fuel temp (and pressure) sensor 10 DDE 4 Volume control valve 11 Fuel restrictor Restrictor The restrictor has a .2 mm orifice which increases the pressure in the fuel return of the fuel injectors. The operating pressure in the leakage oil circuit is about 10 bar. Index Explanation 1 Connection from injector leakage line 2 Filter 3 Restrictor (.2mm) 4 Filter 5 Connection to low pressure line The fuel flowing from the piezo-fuel injectors via the fuel return connection (1) initially passes through a filter (2), through restrictor (3) and then through a further filter (4) to connection (5) back into the fuel feed to the high pressure pump. There is a filter (2 and 4) on either side of restrictor (3) as the restrictor has no specific direction of flow. The filters ensure that the actual restrictor (3) does not become clogged. Fuel Injector Volume Adjustment Piezo-fuel injectors not only bear the hydraulic tolerances but also information concerning the stroke characteristics of the injector. This is a separate classification for the injector voltage calibration. This information is necessary due to the individual voltage reguire- ment of each fuel injector. The fuel injector is assigned to a voltage reguirement class. This replaces the seventh digit of the numerical combination on the injector for hydraulic adjustment. A piezo-fuel injector therefore has only six characters for the hydraulic adjustment (due to a more precise manufacture of the piezo-fuel injectors) and a seventh character for the injector voltage adjustment. Index Explanation 1 7 Character code for adjustment 2 Voltage adjustment Zero volume adaptation must be carried out on a continual basis due to the volume drift of the fuel injectors. At each cylinder, a small amount of fuel is injected during overrun mode. This volume continues to increase until a slight increase in engine speed is detected by the digital diesel electronics. The digital diesel electronic is thus able to detect when the respec¬ tive cylinder begins to work. The volume of fuel injected during zero volume adaptation is used by the digital diesel electronics as a value for the characteristic map of pre-injection. Zero volume adaptation takes place alternately from one cylinder to the next during the overrun phase at engine speeds from 1500 to 2500 rpm and with the engine at operating temperature. Zero volume adaptation has no influence on fuel consumption as only very small guantity of fuel (about Imm^) is injected at one cylinder at a time. Volume Adjustment If the digital diesel electronics detects engine speed fluctuations, the actuation period of the fuel injectors is corrected based on these engine speed fluctuations. The volume adjustment adapts the injected volume of all cylinders with respect to each other. Zero Volume Adaptation The zero volume adaptation is a continual learning process. This learning process is reguired to enable precise pre-injection for each individual fuel injector. Accurate metering of the very low pre-injection volume is necessary for the fulfilment of exhaust emission regulations. Advanced Diesel Technology 61 62 Advanced Diesel Technology Mean Volume Adaptation The mean volume (quantity) adaptation is a learning process in which the air/fuel ratio (lambda value) is corrected by the adjust¬ ment of the air mass or exhaust gas recirculation. Unlike the other processes, this process affects all fuel injectors equally rather than the individual fuel injector. An injection volume averaged across all cylinders is calculated from the lambda value measured by the oxygen sensor and the air mass measured by the hot-film air mass meter. This value is compared with the injection volume specified by the digital diesel electronics. If a discrepancy is detected, the air mass is adjusted to match the actual injection volume by an adjustment of the exhaust gas recirculating valve. The correct lambda value is set in turn. The mean volume adaptation is not an "instantaneous" regulation but an adaptive learning process. The injection volume error is taught into an adaptive characteristic map that is permanently stored in the EEPROM of the control unit. Replacing the following components will require a reset (clearance) of this mean volume adaptation characteristic map: • Hot-film air mass meter • Fuel injector(s) • Rail pressure sensor It is possible to reset the characteristic map with the BMW diagnosis system. Advanced Diesel Technology 63 64 Advanced Diesel Technology Workshop Exercise - Fuel Supply System 1. Fill in the chart below while performing the test module for the EKP: Item Value Voltage, fuel pump Current, fuel pump Specified delivery rate 2. Carry out the service function for bleeding the fuel system. When would this procedure be required? 3. Carry out the plausibility test for the fuel pressure/temperature sensor: Item Value Fuel temperature Fuel pressure (E70 only) Workshop Exercise - High Pressure Fuel System Component Location / Identification \S_ 1. Complete the chart by filling in the functions for the listed components, then locate on the vehicle: Index Explanation Function/Purpose A Fuel feed (low pressure) B Fuel return C Fuel high pressure 1 Fuel rail pressure sensor 2 High pressure line 3 Leakage line 4 Piezo injector 5 Fuel rail pressure control valve 6 Return line 7 Feed line 8 Fuel temperature (or temp/pressure) 9 High pressure line 10 Fuel rail 11 Restrictor 12 High pressure pump 13 Volume control valve Advanced Diesel Technology 65 66 Advanced Diesel Technology Workshop Exercise - High Pressure Fuel System 1. Using the “read measured values” test modules in service functions, please complete the following table: 2. With the engine at operating temperature, please complete the following table regarding the rail pressure. Engine speed Rail pressure (actual) Activation pressure, control valve Activation, volume control valve Idle 1000 rpm 2000 rpm 3000 rpm Workshop Exercise - High Pressure Fuel System 3. Disconnect the rail pressure sensor and note the substitute value. Is there any change to engine operation? Substitute value - 4. Complete the test module for the rail pressure regulation valve. Record the resistance values in the chart below: Nominal value Actual value 5. Disconnect the volume control valve. Does the engine run? Explain why or why not? 6. Disconnect the pressure control valve? Does the engine run? Explain why or why not? Advanced Diesel Technology 67 68 Advanced Diesel Technology Workshop Exercise - High Pressure Fuel System 7 . Perform the test module for the high pressure pump and complete the following chart: Amplitude (maximum) Period duration While performing above test module, obtain the oscilloscope pattern for the high pressure pump. Draw the pattern on the scope illustration provided. Pnnt Change End I Services BMW Measuring system Oscilloscope display T r i g g e r I e V e Cotnier ILhiuzi^J Help nttUCl 1 jtJhar**B j 1 AineMuo;. C'inri k A Amel'tuce Chanra a 1 I Tiir^ vaue Stimciaot | !► Item Value Test connections (MFK) Frequency settings Voltage level Trigger level Workshop Exercise - High Pressure Fuel System 8 . Obtain an oscilloscope pattern of the piezo injector and sketch your result below: WARNING!!! High voltage may be present. BMW Measuring system Oscilloscope display A [V] ◄ Cir\cr 1 ry '(.rjcf? IH 8 IV] V ▲ ▲ [▲ ——— x ▼ ▼ 3 B ms T r i g g e r I e v e I MJtimoler I Courtat [1 Cscilouoopa Simulators 1 1 a nK«t lr 1 (I cutting J 11 '■watumurq | I* 'Churn* « AmpliMJi cn nnnri ■*» Ampl.tuOa C-ti jrn^i S Time vdue Record Settings in the chart below: Item Value Test connections (MFK) Frequency settings Voltage level Trigger level 9. Measure the resistance values of all injectors and record below: Injector 1 Injector 2 Injector 3 Injector 4 Injector 5 Injector 6 Advanced Diesel Technology 69 70 Advanced Diesel Technology Workshop Exercise - High Pressure Fuel System 10. Perform the test module/service function for the fuel injectors and complete the following table with the correct classification numbers and compare to those on the vehicle: Cylinder number Classification 1 2 3 4 5 6 What type of fuel injectors are used in the M57D30T2 engine? Advanced Diesel Technology 71 72 Advanced Diesel Technology ^ Classroom Exercise - Review Questions 1. Which of the components listed below direct fuel to the return circuit for the operation of the siphon jet in the fuel tank? (circle those that apply) Leakage line Volume control valve Rail pressure control valve Restrictor Fuel injectors Fuel filter 2. In order to refuel a BMW diesel vehicle, there is a flap in the fuel tank to prevent misfueling. What is the correct diameter of the diesel fuel nozzle which is necessary to operate the misfueling flap? (circle one) 19 mm 21mm 24 mm 34 mm 3. Which of the following components is NOT used on a diesel fuel system? (circle those that apply) Electric fuel pump Charcoal canister Fuel filter EKP module Siphon jet DM-TL 4. In order for the piezo injector to operate correctly, the pressure in the leakage circuit must be: (circle one) 100 bar or greater Approximately 10 bar 3 to 5 bar 100 millibar 200 bar 1 bar+/-100 millibar 5. In order to maintain the adeguate pressure in the leakage line, a_is installed after the fuel injectors, (circle one) check valve non-return valve restrictor solenoid bypass valve coupler 6. For the US version of the diesel, which of the following fuel system components has been adapted to meet the US specific fuel specifications? (circle all that apply) High pressure pump Fuel filter Volume control valve Leakage line Electric fuel pump Fuel injectors Fuel rail Fuel filter heater ^ Classroom Exercise - Review Questions 7. Complete the following chart by checking the box for either E70 or E90 where it applies: Component/System E70Xdrive35d E90 335d Screw-spindle fuel pump Gear-type (rotor) fuel pump Speed controlled low pressure fuel system Pressure controlled low pressure fuel system Fuel temperature/pressure sensor Fuel temperature sensor Low pressure EGR system High-pressure EGR system SCR system Diesel particulate filter Low pressure EGR cooler High pressure EGR cooler Advanced Diesel Technology 73 74 Advanced Diesel Technology Diesel Emission Control Systems Legislation Since the first exhaust emission legislation for petrol engines came into force in the mid-1960s in California, the permissible limits for a range of pollutants have been further and further reduced. In the meantime, all industrial nations have introduced exhaust emission legislation that defines the emission limits for petrol and diesel engines as well as the test methods. Essentially, the following exhaust emission legislation applies: • CARB legislation (California Air Resources Board), California • ERA legislation (Environmental Protection Agency), USA • EU legislation (European Union) and corresponding ECE regulations (UN Economic Commission for Europe), Europe • Japan legislation. This legislation has lead to the development of different reguirements with regard to the limitation of various components in the exhaust gas. Essentially, the following exhaust gas constituents are evaluated: • Carbon monoxide (CO) • Nitrogen oxides (NO x ) • Hydrocarbons (HC) • Particulates (PM) It can generally be said that traditionally more emphasis is placed on low nitrogen oxide emissions in US legislation while in Europe the focus tends to be more on carbon monoxide. The following graphic compares the standard applicable to BMW diesel vehicles with the current standards in Europe. A direct comparison, however, is not possible as different measuring cycles are used and different values are measured for hydrocarbons. Although European and US standards cannot be compared 1:1 it is clear that reguirements relating to nitrogen oxide emissions are con¬ siderably more demanding in the US market. Diesel engines generally have higher nitrogen oxide emission levels than petrol engines as diesel engines are normally operated with excess air. For this reason, the challenge of achieving approval in all 50 states of the USA had to be met with a series of new technological developments. Comparison of Exhaust Emission Legislation NOxfmg/km] * In Europe, the sum of nitrogen oxide and hydrocarbons is evaluated, i.e. the higher the HC. ** In the USA, only the methane-free hydrocarbons are evaluated, i.e. all hydrocarbons with no methane. CO[mg/km] Standard Valid from CO [mg/km] NO* [mg/km] HC+NO * [mg/km] NMHC ** [mg/km] PM [mg/km] EURO 4 1-1-05 500 250 300 - 25 EURO 5 9-1-09 500 180 230 - 5 EURO 6 9-1 -14 500 80 170 - 5 LEV II MY 2005 2110 31 - 47 6 PM[mg/km] HU HC[mg/km] NMHC[mg/km] 1030 - 1500 - LEVII Advanced Diesel Technology 75 76 Advanced Diesel Technology Exhaust Gas Recirculation The recycling of exhaust gases is one of the methods used to reduce NO x in a diesel engine. By introducing exhaust gas into the intake stream, the amount of oxygen in the combustion chamber is reduced which results in lower combustion chamber temperatures. The EGR systems differ between the E70 and the E90. Both vehi¬ cles use the “high-pressure EGR”, but the E70 uses an additional “low-pressure EGR” system. The low pressure EGR system is required in the E70 due to it’s additional weight and higher opera¬ tional loads (i.e. towing etc.). Low Pressure EGR The known EGR system has been expanded by the low pressure EGR on the E70. This system offers advantages particularly at high loads and engine speeds. This is why it is used in the heavier E70 as it is often driven in the higher load ranges. The advantage is based on the fact that a higher total mass of exhaust gas can be recirculated. This is made possible for two reasons: • Lower exhaust gas temperature - The exhaust gas for the low pressure EGR is tapped off at a point where a lower tempera¬ ture prevails than in the high pressure EGR. Consequently, the exhaust gas has a higher density thus enabling a higher mass. In addition, the exhaust gas is added to the fresh intake air before the exhaust turbocharger, i.e. before the intercooler, where it is further cooled. The lower temperature of the total gas enables a higher EGR rate without raising the temperature in the combustion chamber. • Recirculation before the exhaust turbocharger - Unlike in the high pressure EGR where the exhaust gas is fed to the charge air already compressed, in this system the exhaust gas is added to the intake air before the exhaust turbocharger. A lower pressure prevails in this area under all operating condi¬ tions. This makes it possible to recirculate a large volume of exhaust gas even at higher engine speed and load whereas this is limited by the boost pressure in the high pressure EGR. Low pressure EGR system The following graphic shows the control of the EGR system with The low pressure EGR system is located on the right-hand side on low pressure EGR: the engine directly next to the diesel particulate filter and the low pressure stage of the turbo assembly. The exhaust gas is branched off directly after the diesel particulate filter and fed to the intake air before the compressor for the low pressure stage. Index Explanation Index Explanation 1 No EGR 3 High and low pressure EGR are active 2 Only high pressure EGR is active As already mentioned, the low pressure EGR has the greatest advantage at higher loads and is therefore activated, as a function of the characteristic map, only in this operating mode. Index Explanation Index Explanation 1 DPF 4 Low pressure EGR 2 Turbocharger assembly 5 Exhaust system 3 Exhaust turbocharger, low pressure stage The low pressure EGR, however, is never active on its own but rather always operates together with the high pressure EGR. Added to this, it is only activated at a coolant temperature of more than 55°C. The low pressure EGR valve is closed as from a certain load level so that only the high pressure EGR valve is active again. This means the EGR rate is continuously reduced. Advanced Diesel Technology 77 78 Advanced Diesel Technology The following graphic shows the components of the low pressure EGR: Index Explanation Index Explanation 1 Temperature sensor - LP EGR 5 Coolant infeed 2 LP-EGR valve 6 Coolant return 3 Connection for positional feedback 7 LP-EGR cooler 4 Vacuum unit for LP-EGR valve 8 Sheet metal gasket with filter There is a fine meshed metal screen filter located at the exhaust gas inlet from the diesel particulate filter to the low pressure EGR system. The purpose of this filter is to ensure that no particles of the coating particularly in a new diesel particulate filter can enter the low pressure EGR system. Such particles would adversely affect the compressor blades of the exhaust turbocharger. The metal screen filter must be installed when fitting the low pres¬ sure EGR cooler to the diesel particulate filter otherwise there is a risk of the turbocharger being damaged. Index Explanation Index Explanation 1 Cleaned blow-by gas 3 Intake manifold 2 Ventilation, naturally aspirated operation 4 Clean-air pipe Exhaust Turbocharger The US engine is eguipped with the same variable twin turbo as the European version, however, the turbo assembly is modified due to the low pressure EGR. On the one hand, the inlet for the low pressure EGR is located on the compressor housing for the low pressure stage. On the other hand, the compressor wheels are nickel-coated to protect them from the exhaust gas. High Pressure EGR The exhaust gas recirculation known to date is referred to here as the high pressure EGR in order to differentiate it from the low pressure EGR. Compared to the European version, the high pressure EGR is eguipped with the following special features: • Electric EGR valve with positional feedback • Temperature sensor before high pressure EGR valve • EGR cooler with bypass. © © ® > ® ® ® Index Explanation Index Explanation 1 Coolant inlet 5 High pressure EGR cooler 2 High pressure EGR valve 6 Vacuum unit of bypass valve for HP- EGR cooler 3 Throttle valve 7 Coolant return 4 Temperature sensor, HP-EGR The electric actuating system of the EGR valve enables exact metering of the recirculated exhaust gas guantity. In addition, this quantity is no longer calculated based solely on the signals from the hot-film air mass meter and oxygen sensor but the following signals are also used: • Travel of high pressure EGR valve • Temperature before high pressure EGR valve • Pressure difference between exhaust gas pressure in the exhaust manifold and boost pressure in the intake manifold. This enables even more exact control of the EGR rate. The EGR cooler serves the purpose of increasing the efficiency of the EGR system. However, reaching the operating temperature as fast as possible has priority at low engine temperatures. In this case, the EGR cooler can be bypassed in order to heat up the combustion chamber faster. For this purpose, there is a bypass that diverts the flow of the exhaust around the EGR cooler. This bypass is actuated by a flap which, in turn, is operated by a vacuum unit. The bypass is either only in the "Open" or "Closed" position. Advanced Diesel Technology 79 80 Advanced Diesel Technology Selective Catalytic Reduction In order to comply with stringent EPA guidelines, the new Selective Catalytic Reduction (SCR) system is installed in the new diesel vehicles from BMW. The M57D30T2 engine complies with the EPA Tier 2, Bin 5 reguirements. This allows the new diesel vehicles to be sold in all 50 states. The SCR system is a recently new development in the automotive industry, but this technology has been in use by coal fired power plants for many years. The term “selective” indicates that the reducing agent prefers to oxidize selectively with the oxygen contained in the nitrogen oxides instead of the oxygen present in the exhaust gas. The reducing agent is injected into the exhaust system where it is converted to ammonia and carbon dioxide. The resulting ammonia is used within a special catalyst in the exhaust stream. The resulting reaction converts the unwanted oxides of nitrogen into harmless nitrogen and water. The preferred reducing agent in an SCR system is ammonia (NH 3 ). However, ammonia by itself is toxic and would not be practical or safe to carry in the vehicle. So, an alternative would be a safer “carrier” substance which, in this case, is a urea/water compound. Urea, (NH 2 ) 2 CO, is commonly used as a fertilizer and is biologically compatible with groundwater and chemically stable for the environ¬ ment. This allows urea to be used as the reducing agent in the SCR system. The ammonia is then extracted from the urea during an “on-board” chemical reaction which takes place once the urea is injected into the exhaust system. The official name for the reducing agent is Diesel Exhaust Fluid or DEF. This is the name that will be used in the owner’s manual and in this training material. See note below: Important note on DEF In this training material, there are several terms which are in use for DEF. Some of these terms include reductant, reducing agent or urea/water solution. The technical name used industrywide is AUS32, which is a urea/water solution of which urea comprises 32.5% of the mix¬ ture. Another term which is used is AdBlue, which is the registered trademark for AUS32. However, there are other producers of AUS32. AdBlue is just one of them. The AdBlue trademark is currently held by the German Association of the Automobile Industry (VDA), who ensure guality standards are maintained in accordance with DIN 70070 specifications. SCR Overview - Simplified Selective catalytic reduction is a system for reducing nitrogen oxides (NO x ) in the exhaust gas. For this purpose, a reducing agent (urea/water solution) is injected into exhaust gas downstream of the diesel particulate filter. The nitrogen oxide reduction reaction then takes place in the SCR catalytic converter. The urea-water solution is carried in two reser¬ voirs in the vehicle. The guantity is measured out such that it is sufficient for one oil change interval. The following graphic shows a simplified representation of the system: 0 0 /^=a jr - 2 ( y= Index Explanation Index Explanation 1 Passive reservoir 10 Transfer pump 2 Level sensors 11 Filter 3 Filler pipe, passive tank 12 Transfer line 4 Metering line 13 Metering module 5 Metering line heater 14 Level sensor 6 Pump 15 Filler pipe, active reservoir 7 Function unit 16 Exhaust system 8 Heater, in active tank 17 SCR catalytic converter 9 Active tank The reason for using two reservoirs is that the urea-water solution freezes at a temperature of -11 °C (12.2°F). For this reason, the smaller “active” reservoir is heated but the larger passive reservoir is not. In this way, the entire volume of the urea-water solution need not be heated, thus saving energy. The amount in the active tank is sufficient, however, to cover large distances. The small, heated reservoir is referred to as the active reservoir. A pump conveys the urea-water solution from this reservoir to the metering module. This line is also heated. The larger, unheated reservoir is the passive reservoir. A transfer pump regularly conveys the urea-water solution from the passive reservoir to the active reservoir. Advanced Diesel Technology 81 82 Advanced Diesel Technology SCR System Components Index Explanation Index Explanation 1 Active tank 8 Passive tank 2 Delivery module 9 Metering module 3 Filler for active tank 10 Exhaust gas temp sensor - post DPF 4 Transfer pump 11 NO x sensor - pre SCR catalyst 5 Filter 12 Filler neck for passive tank 6 SCR catalyst 13 DOC/DPF 7 NO x sensor - post SCR catalyst Component Location - E70 On the E70, the active reservoir, including the delivery unit, is locat¬ ed on the right-hand side directly behind the front bumper panel. The passive reservoir is located on the left in the underbody, approximately under the driver's seat. The transfer unit is installed on the right in the underbody. Both fillers are located in the engine compartment. Component Location - E90 On the E90, both the active reservoir as well as the passive reser¬ voir are located under the luggage compartment floor with the active reservoir being the lowermost of both. The fillers are located on the left-hand side behind the rear wheel where they are accessible through an opening in the bumper panel The fillers are arranged in the same way as the reservoirs, i.e. the lower most is the filler for the active reservoir. The transfer unit and the filter are located behind the filler. Index Explanation Index Explanation 1 Active tank 8 Passive tank 2 Delivery module 9 Metering module 3 Filler for active tank 10 Exhaust gas temp sensor - post DPF 4 Transfer pump 11 NO x sensor - pre SCR catalyst 5 Filter 12 Filler neck for passive tank 6 SCR catalyst 13 DOC/DPF 7 NO x sensor - post SCR catalyst Advanced Diesel Technology 83 84 Advanced Diesel Technology Passive Reservoir The passive reservoir is the larger of the two supply reservoirs. The name passive reservoir refers to the fact that it is not heated. The following components make up the passive reservoir: • Level sensors (2x) • Operating vent (2x on E90) • Filler vent. Index Explanation Index Explanation 1 Operating vent 5 Fill line connection 2 Filler vent 6 “empty” level sensor 3 “full” level sensor 7 Passive reservoir 4 Operating vent The passive reservoir on the E70 is encased in insulation as it is positioned near the front of the exhaust system where the heat transfer to the urea-water solution would be very high. Index Explanation Index Explanation 1 Connection for transfer line 5 Fill line connection 2 Operating vent 6 Filler vent 3 “full” level sensor 7 “empty” level sensor 4 Passive reservoir Vehicle Volume Location Position of filler neck E70 16.5 1 In underbody, under driver’s seat (approximately) In the engine compartment, left side, under unfiltered air inlet E90 14.4 1 Under luggage compartment floor Left side in rear bumper Level Sensors There are two level sensors in the passive reservoir. One supplies the "Full" signal and the other the "Empty" signal. The sensors make use of the con¬ ductivity of the urea-water solution. When these contacts are wetted with urea-water solution the circuit is closed and current can flow, thus enabling a sensor signal. The two level sensors send their signal to an evaluator. This evalu¬ ator filters the signals and recognizes, for example, sloshing of the urea-water solution and transfers a corresponding level signal to the digital diesel electronics. The "Full" level sensor is located at the top of the passive reservoir. Both contacts are wetted when the passive reservoir is completely filled and the sensor sends the "Full" signal. The "Empty" level sensor is located at the bottom end of the pas¬ sive reservoir. The reservoir is considered to be "not empty" for as long as the sensor is covered by urea-water solution. The evaluator detects that the passive reservoir is empty when no sensor signal is received. Transfer Unit The transfer unit pumps the urea-water solution from the passive reservoir to the active reservoir. There is a screen filter in the inlet port of the pump. This pump is designed as a diaphragm pump. It operates in a similar way to a piston pump but the pump element is separated from the medium by a diaphragm. This means there are no prob¬ lems regarding corrosion. Index Explanation 1 Connection for transfer line to passive reservoir (inlet) 2 Electrical connection for pump motor 3 Connection for transfer line to active reservoir (outlet) Venting The passive reservoir is eguipped with one operating vent (2 in the E90) and one filler vent. The operating vent is directed into the atmosphere. A so-called sintered filter tablet ensures that no impu¬ rities can enter the reservoir via the operating vent. This sintered tablet consists of a porous material and serves as a filter that allows particles only up to a certain size to pass through. The filler vent is directed into the filler pipe and therefore no filter is reguired. Advanced Diesel Technology 85 86 Advanced Diesel Technology Active Reservoir The active reservoir is the smaller of the two reservoirs and its name refers to the fact that it is heated. In view of its small volume, little energy is required to heat the urea-water solution. Index Explanation Index Explanation 1 Active reservoir 4 Filler vent 2 Operating vent 5 Fill line connection 3 Delivery module 6 Connection of transfer line from passive reservoir Index Explanation 1 Fill line connection, active reservoir 2 Delivery module 3 Metering line 4 Filler vent 5 Connection of transfer line from passive reservoir 6 Active reservoir Active reservoir - E70 Vehicle Volume Location Position of filler neck E70 6.4 1 On front, right side in side panel module between bumper panel and wheel arch In the engine compartment, on the front right hand side E90 7.4 1 Behind rear axle differential, directly under the passive reservoir Left side in rear bumper panel Function Unit The so-called function unit is located in the active reservoir. It has the external appearance of a surge chamber and accommodates a heater, filter and a level sensor. The delivery unit is attached to it. The temperature sensor provides the signal for the heating control system. It is designed as an NTC sensor (negative temperature coefficient). The temperature sensor is integrated at the bottom end of the level sensor. Unlike a surge chamber in the fuel tank, the lower section of the function unit has slots. This chamber creates a smaller volume in the reservoir that scarcely mixes with the urea-water solution outside the chamber. There is a PTC heating element (positive temperature coefficient) in the base of the chamber that can heat up this smaller volume at a relatively fast rate. The intake line is also heated. In this way, the liquid urea-water solution can be made available for vehicle opera¬ tion even at the lowest temperatures. Index Explanation 1 Operating vent 2 Bowl 3 Level sensor 0 0 Index Explanation Index Explanation 1 Level sensor 4 Intake line with heater 2 Heating element 5 Operating vent 3 Filter The heating element in the chamber is connected to the heater for the intake line to form one heating circuit. A power semiconductor supplies the current for this heating circuit. The power semicon¬ ductor is controlled by the DDE. The DDE can determine the current that flows across the heating elements and can therefore monitor their operation. Advanced Diesel Technology 87 88 Advanced Diesel Technology Level Sensor The level sensor in the function unit provides the level value for the entire active reservoir. The level sensor in the active reservoir operates in accordance with the same principle as the level sen¬ sors in the passive reservoir. In this case, however, there is only one sensor with several contacts that extend at different levels into the active reservoir. The sensor makes use of the conductivity of the urea-water solution. A total of four contacts project into the reservoir. When these contacts are wetted with urea-water solution the circuit is closed and current can flow, thus enabling a sensor signal. Three contacts are responsible for signalling the different levels. The fourth contact is the reference, i.e. the contact via which the electric circuit is closed. This reference contact cannot be seen in the figure as it is located directly behind the "Empty" contact (3). 3': The level sensor sends its signal to an evaluator. This evaluator filters the signal and recognizes, for example, sloshing of the urea- water solution and transfers a corresponding level signal to the digital diesel electronics. v“ Ik. y Index Explanation 1 “Full contact” 2 Warning contact 3 “Empty contact” Delivery Unit The delivery unit is located on the active reservoir at the top end of the function unit. Among other things, the delivery unit comprises the pump that transfers the urea-water solution from the active reservoir to the metering module. The delivery unit is also heated by a PTC element. Index Explanation Index Explanation 1 Pump motor and heater electrical connection 3 Pressure sensor electrical connection 2 Reversing valve electrical connection 4 Metering line fluid connection The heating element in the delivery unit is connected to the heater for the metering line to form one heating circuit. A power semi¬ conductor supplies the current for this heating circuit. The power semiconductor is controlled by the DDE. The DDE can determine the current that flows across the heating elements and can there¬ fore monitor their operation. Pump The pump is a common part with the pump in the transfer unit. While the engine is running, it pumps the urea-water solution from the active reservoir to the metering module. It draws the metering line empty when the engine is turned off. Pressure Sensor The pressure sensor measures the pressure in the delivery line to the metering module. The value is transferred to the DDE. Reversing Valve The reversing valve ensures the delivery direction in the metering line can be reversed to empty the metering line while the pump delivers in the same direction. It is designed as a 4/2-way valve interchanges the metering line and intake line to the pump. The valve is not actuated in intervals and therefore has only two positions. Since power is permanently applied to the valve when it is actuated, the maximum actuation time is limited in order to avoid overheating. Advanced Diesel Technology 89 90 Advanced Diesel Technology Metering Module and Mixer The metering module is responsible for injecting the urea-water solution into the exhaust pipe. It features a valve that is similar to the fuel injector in a petrol engine with intake manifold injection. © ® Index Explanation Index Explanation 1 Metering line connection 2 Metering valve connection Although the metering module does not have a heater, it is still heated by the exhaust system to such an extent that it even reguires cooling fins. The metering module is actuated by a pulse-width modulated (PWM) signal from the DDE such that the pulse duty factor deter¬ mines the opening duration of the valve. The metering module is eguipped with a tapered insert (6) that prevents urea-water solution residue drying up and clogging the valve. Its shape creates a flow that prevents urea-water solution from collecting on the walls of the exhaust system. Urea deposits on the insert are burnt off as it is heated to very high temperatures by the flow of exhaust gas. Index Explanation Index Explanation 1 Mixer 4 DPF 2 NO x sensor - pre SCR catalyst 5 Metering module 3 Exhaust gas temperature sensor after DPF 6 Insert Mixer The mixer mounted in the flange connection of the exhaust pipe is located directly behind the metering module in the exhaust system. It swirls the flow of exhaust gas to ensure the urea-water solution is thoroughly mixed with the exhaust gas. This is necessary to ensure the urea converts completely into ammonia. N0 X Sensors The nitrogen oxide sensor consists of the actual measuring probe and the corresponding control unit. The control unit communi¬ cates via the LoCAN with the engine control unit. In terms of its operating principle, the nitrogen oxide can be com¬ pared with a broadband oxygen sensor. The measuring principle is based on the idea of basing the nitrogen oxide measurement on oxygen measurement. The exhaust gas flows through the NO x sensor. Here, only oxygen and nitrogen oxides are of interest. In the first chamber, the oxygen is ionized out of this mixture with the aid of the first pump cell and passed through the solid electrolyte. A lambda signal can be tapped off from the pump current of the first chamber. In this way, the exhaust gas in the NO x sensor is liberated from free oxygen (not bound to nitrogen). The remaining nitrogen oxide then passes through the second barrier to reach the second chamber of the sensor. Here, the nitro¬ gen oxide is split by a catalytic element into oxygen and nitrogen. The oxygen released in this way is again ionized and can then pass through the solid electrolyte. The pump current that occurs during this process makes it possible to deduce the guantity of oxygen and the nitrogen level can be concluded from this guantity. The following graphic shows the functional principle of this measuring system. 1 ] 2 i Index Explanation Index Explanation 1 Pump flow, 1 st chamber 5 Barrier 2 2 Catalytic element 6 Solid electrolyte Zircon dioxide (Zr0 2 ) 3 Nitrogen outlet 7 Barrier 1 4 Pump flow 2nd chamber Advanced Diesel Technology 91 92 Advanced Diesel Technology Functions of the SCR System Selective catalytic reduction is currently the most effective system for reducing nitrogen oxides (NO x ). During operation, it achieves an efficiency of almost 100% and approximately 90% over the entire vehicle operating range. The difference is attributed to the time the system reguires until it is fully operative after a cold start. 0 ® 0 Index Explanation Index Explanation 1 NO x sensor, pre catalyst 3 NO x sensor, post catalyst 2 Metering module 4 Temperature sensor after DPF This system carries a reducing agent, urea-water solution, in the vehicle. The urea-water solution is injected into the exhaust pipe by the metering module upstream of the SCR catalytic converter. The DDE calculates the guantity that needs to be injected. The nitrogen oxide content in the exhaust gas is determined by the NO x sensor before the SCR catalytic converter. Corresponding to this value, the exact guantity of the urea-water solution required to fully reduce the nitrogen oxides is injected. The urea-water solution converts to ammonia in the exhaust pipe. In the SCR catalytic converter, the ammonia reacts with the nitrogen oxides to produce nitrogen (N 2 ) and water (H 2 O). A further NO x sensor that monitors this function is located down¬ stream of the SCR catalytic converter. A temperature sensor in the exhaust pipe after the diesel particu¬ late filter (i.e. before the SCR catalytic converter) and the metering module also influences this function. This is because injection of the urea-water solution only begins at a minimum temperature of 200°C (392°F). Chemical Reaction The task of the SCR system is to substantially reduce the nitrogen oxides (NO x ) in the exhaust gas. Nitrogen oxides occur in two different forms: • Nitrogen monoxide (NO) • Nitrogen dioxide (NO 2 ). NO N0 2 Ammonia (NH 3 ) is used for the purpose of reducing the nitrogen oxides in a special catalytic converter. The ammonia is supplied in the form of a urea-water solution. nh 3 Urea-water solution 1 1 i The urea-water solution is injected by the metering system into the exhaust system downstream of the diesel particulate filter. The reguired guantity must be metered exactly as otherwise nitrogen oxides or ammonia would emerge at the end. The following description of the chemical processes explains why this is the case. Conversion of the Urea-water Solution The uniform distribution of the urea-water solution in the exhaust gas and the conversion to ammonia take place in the exhaust pipe upstream of the SCR catalytic converter. Initially, the urea ((Nh^^CO) dissolved in the urea-water solution is released. The conversion of urea into ammonia takes place in two stages. [=» (NHzkCO Release of Urea from urea-water solution Advanced Diesel Technology 93 KU 8001 94 Advanced Diesel Technology Thermolysis Explanation: During thermolysis, the urea-water solution is split into two products as a result of heating Initial Products: Urea (NH 2 ) 2 CO Result: Ammonia (NH 3 ) Isocyanic acid (HNCO) Chemical Formulas: (NH 2 ) 2 CO > NH 3 = HNCO Thermolysis: Urea converts to ammonia and isocyanic acid This means, only a part of the urea-water solution is converted into ammonia during thermolysis. The remainder, which is in the form of isocyanic acid, is converted in a second step. Hydrolysis Explanation: The isocyanic acid that was produced during thermoly¬ sis is converted into ammonia and carbon dioxide (C0 2 ), by the addition of water in the hydrolysis process. Initial Products: Isocyanic acid (HNCO) Water (H 2 0) Result: Ammonia (NH 3 ) Carbon dioxide (C0 2 ) Chemical Formulas: hnco + h 2 o>nh 3 + co 2 Hydrolysis: Isocyanic acid reacts with water to form ammonia and carbon dioxide HNCO H 2 0 NH 3 CO 2 The water required for this purpose is also provided by the urea-water solution. Therefore, following hydrolysis, all the urea is converted into ammonia and carbon dioxide. N0 X Reduction Nitrogen oxides are converted into harmless nitrogen and water in the SCR catalytic converter. Reduction Explanation: The catalytic converter serves as a "docking" mecha¬ nism for the ammonia molecules. The nitrogen oxide molecules meet the ammonia molecules and the reaction starts and energy is released. This applies to NO in the same way as to N 02 - Initial Products: Ammonia (NH 3 ) Nitrogen monoxide (NO) Nitrogen dioxide (NO 2 ) Oxygen (0 2 ) Result: Nitrogen (N 2 ) Water (H 2 0) Chemical Formulas: NO + N0 2 + 2NH 3 > 2N 2 + 3H 2 0 4NO + 0 2 + 4NH 3 > 4N 2 + 6H 2 0 6N0 2 + 8 NH 3 > 7N 2 + 12H 2 0 4x % + C* •=• + NO N0 2 NH 3 N 2 H 2 0 a 4» 9 4x 6x ® ® ®=® + NO 0 2 NH 3 N 2 H 2 0 6x v»+ “!■►«+>. N0 2 nh 3 n 2 h 2 o NO x reduction: Nitrogen oxides react with ammonia to form nitrogen and water It can be seen that each individual atom has found its place again at the end of the process, i.e. exactly the same elements are on the left as on the right. This takes place only when the ratio of the urea-water solution to nitrogen oxides is correct. Nitrogen oxides would emerge if too little urea-water solution were injected. By the same token, ammonia would emerge if too much urea-water solution were injected, resulting in unpleasant odor and possible damage to the environment. Advanced Diesel Technology 95 96 Advanced Diesel Technology SCR Control The SCR control is integrated in the digital diesel electronics (DDE). The SCR control is divided into the metering system control and the metering strategy. Index Explanation Index Explanation 1 DDE 7.3 10 Pressure sensor 2 SCR control 11 Temperature sensor in active reservoir 3 Metering system control 12 Outside temperature sensor 4 Metering strategy 13 Level sensor in active reservoir 5 Injection pump 14 Level sensor in passive reservoir 6 Transfer pump 15 NO x sensor - pre SCR catalyst 7 Metering module 16 NO x sensor - post SCR catalyst 8 Heater 17 Exhaust temperature sensor 9 Reversing valve Metering Strategy The metering strategy is an integral part of the SCR control that calculates how much urea-water solution is to be injected at what time. Index Explanation A Value from NO x sensor B Injected quantity of urea-water solution 1 Too-little urea-water solution injected 2 Correct quantity of urea-water solution injected 3 Too-much urea-water solution injected The NO x sensor, however, measures not only nitrogen oxides but also ammonia but cannot distinguish between them. If too much urea-water solution is injected, although the nitrogen oxides are completely reduced so-called "ammonia slip" occurs, i.e. ammonia emerges from the SCR catalytic converter. This in turn causes a rise in the value measured by the NO x sensor. The aim, therefore, is to achieve a minimum of the sensor value. This, however, is a long-term adaptation and not a short-term con¬ trol process as the SCR catalytic converter performs a storage function for ammonia. During normal operation, the signal from the NO x sensor before the SCR catalytic converter is used for the purpose of calculating the guantity. This sensor determines the guantity of nitrogen oxide in the exhaust gas and sends the corresponding value to the DDE. However, the NO x sensor must reach its operating temperature before it can start measuring. Depending on the temperature, this can take up to 15 minutes. Until then the DDE uses a substitute value to determine the amount of nitrogen oxide in the exhaust gas. A second NO x sensor is installed after the SCR catalytic converter for the purpose of monitoring the system. It measures whether there are still nitrogen oxides in the exhaust gas. If so the injected guantity of the urea-water solution is correspondingly adapted. Advanced Diesel Technology 97 98 Advanced Diesel Technology Metering System Control The metering system control could be considered as the executing part. It carries out the reguirements set by the metering strategy. This includes both the metering, i.e. injection as well as the supply of the urea-water solution. The tasks of the metering system control during normal operation are listed in the following: Metering of the urea-water solution: • Implementation of the reguired target guantity of urea-water solution • Feedback of the implemented actual guantity of urea-water solution. Supplying urea-water solution: • Preparation of metering process (filling lines and pressure built-up) under corresponding ambient conditions (tempera¬ ture) • Emptying lines during afterrunning • Heater actuation. In addition, the metering system control recognizes faults, implausi¬ ble conditions or critical situations and initiates corresponding measures. Metering of the Urea-water Solution The metering strategy determines the guantity of urea-water solution to be injected. The metering system control executes this reguest. A part of the function is metering actuation that deter¬ mines the actual opening of the metering valve. Depending on the engine load, the metering valve injects at a rate of 0.5 Hz to 3.3 Hz. The metering actuation facility calculates the following factors in order to inject the correct guantity: • The duty factor of the actuator of the metering valve in order to determine the injection duration • Actuation delay to compensate for the reaction time of the metering valve. The signal from the pressure sensor in the metering line is taken into account to ensure an accurate calculation; the pressure, however, should remain at a constant 5 bar. The metering system control also calculates the guantity actually metered and signals this value back to the metering strategy. The metering guantity is also determined over a longer period of time. This long-term calculation is reset during SCR refilling or can be reset by the BMW diagnosis system. Supplying Urea-water Solution A supply of a urea-water solution is required for the selective cat¬ alytic reduction process. It is necessary to store this medium in the vehicle and to make it available rapidly under all operating condi¬ tions. In this case “making available” means that the urea-water solution is applied at a defined pressure at the metering valve. Various functions that are described in the following are required to carry out this task. Heater The system must be heated as the urea-water solution freezes at a temperature of -11 °C. The heating system performs following tasks: • To monitor the temperature in the active reservoir and the ambient temperature • To thaw a sufficient quantity of urea-water solution and the components required for metering the solution during system startup • To prevent the relevant components freezing during operation • To monitor the components of the heating system. The following components are heated: • Surge chamber in active reservoir • Intake line in active reservoir • Delivery module (pump, filter, reversing valve) • Metering line (from active reservoir to metering module). The heating systems for the metering line and delivery module are controlled dependent on the ambient temperature. The heater in the active reservoir is controlled as a function of the temperature in the active reservoir. The heating control is additionally governed by the following conditions: Temperature in active reservoir and ambient temperature are the same Condition 1 Condition 2 Condition 3 Condition 4 Ambient temperature and temperature in active reservoir > -4°C <-4°C < -5°C < -9°C Metering line heater Not active Not active Active Active Active reservoir heater Not active Active Active Active Metering standby Established Established Established Delayed Metering standby is delayed at a temperature below -9°C in the active reservoir, i.e. a defined waiting period is allowed to elapse until an attempt to build up pressure begins. This time is constant from -9°C to -16.5°C as it is not possible to determine to what extent the urea-water solution is frozen. At temperatures below -16.5°C, the heating time is extended until an attempt to build up the pressure is made. Heating the metering line generally takes place much faster. Therefore, the temperature in the active reservoir is the decisive factor for the period of time until an attempt to build up the pressure is undertaken. However, it is possible that the heating time for the metering line is longer at ambient temperature considerably lower than the temper¬ ature in the active reservoir. In this case, the ambient temperature is taken for the delay in metering standby. Advanced Diesel Technology 99 100 Advanced Diesel Technology The following graphic shows the delay as a function of the temper¬ ature sensor signals. Index Explanation Index Explanation A Delay as a function of temperature in active reservoir B Delay as a function of ambient temperature t[s] Delay time in seconds T[°C] Temperature in degrees Celsius The graphic shows that, with the same temperature signals, the delay time relating to the temperature in the active reservoir is longer than the delay caused by the ambient temperature. Only the times at temperatures below -9°C are relevant as they are shorter than 3 minutes at temperatures above -9°C. 3 minutes is the time that the entire system reguires to establish metering standby (e.g. also taking into account the temperature in the SCR catalytic converter). This is also the time that is approved by the EPA (Environmental Protection Agency) as the preliminary period under all operating conditions. This time is extended significantly at very low tempera¬ tures. The following example shows how the delay time up to metering standby is derived at low temperatures. Example: Ambient temperature: -30°C, temperature in active reservoir: -12°C The vehicle was driven for a longer period of time at very low ambient temperatures of - 30°C. The heater in the active reservoir has thawed the urea-water solution. The vehicle is now parked for a short period of time (e.g. 30 min¬ utes). When restarted, the temperature in the active reservoir is now -12°C. The delay time that is initiated by the temperature in the active reservoir is approximately 18 minutes while the delay time initiated by the ambient temperature is 25 minutes. Since the delay time initiated by the ambient temperature is longer, this will give rise to a longer delay. Now another condition comes into play. Only the end of the delay caused by the temperature in the active reservoir can enable metering. This means: • The delay time initiated by the temperature in the active reser¬ voir will have elapsed after 18 minutes. No enable is yet provided by the second delay caused by the ambient tempera¬ ture. A second cycle of 18 minutes now begins. • The delay time initiated by the ambient temperature will elapse after 25 minutes and will send its enable signal. However, this delay cannot enable metering. • The second cycle of the delay time caused by the tempera¬ ture in the active reservoir will have elapsed after 36 minutes. Since the enable from the delay caused by the ambient tem¬ perature is now applied, metering will be enabled. Transfer Pumping So-called transfer pumping is required since two reservoirs are used for storing the urea-water solution. The term transfer pump¬ ing relates to pumping the urea-water solution from the passive reservoir into the active reservoir. (?) 8 0 (?) (?) Index Explanation Index Explanation 1 Passive reservoir 6 Pump 2 Level sensors 7 Non-return valve 3 Extractor connections 8 Level sensor 4 Transfer line 9 Active reservoir 5 Filter The solution is then pumped fora certain time in order to refill the active reservoir. The transfer pumping procedure is terminated if the "full" level is reached before the time has elapsed. If the passive reservoir was refilled, transfer pumping will only take place after a quantity of approximately 3 liters has been used up in the active reservoir. The entire quantity is then pumped over. The system then waits again until a quantity of approximately 3 liters has been used up in the active reservoir before again pumping the entire quantity while simultaneously starting the incor¬ rect refilling detection function. This function determines whether the system has been filled with the wrong medium as it is present in high concentration in the active reservoir. Transfer pumping does not take place in the event of a fault in the level sensor system. The following conditions must be met for transfer pumping: • There is a urea-water solution in the passive reservoir • The ambient temperature is above a minimum value of -5°C for at least 10 minutes • A defined quantity (300 ml) was used up in the active reservoir or the reserve level in the active reservoir was reached. Advanced Diesel Technology 101 102 Advanced Diesel Technology Delivery The urea-water solution is delivered from the active reservoir to the metering module. This task is performed by a pump that is inte¬ grated in the delivery unit. The delivery unit additionally contains: • Heater • Pressure sensor • Filter • Return throttle • Reversing valve. Index Explanation Index Explanation 1 Metering line 8 Filter 2 Delivery module 9 Level sensor 3 Pump 10 Filter 4 Reversing valve 11 SCR catalyst 5 Filter 12 Exhaust system 6 Restrictor 13 Metering module 7 Pressure sensor The pump is actuated by a pulse-width modulated signal (PWM signal) from the DDE. The PWM signal provides a speed specifica¬ tion for the purpose of establishing the system pressure. The value for the speed specification is calculated by the DDE based on the signal from the pressure sensor. When the system starts up, the pump is actuated with a defined PWM signal and the line to the metering module is filled. This is followed by pressure build-up. Only then does pressure control take place. When the metering line is filled, the opened metering valve allows a small guantity of the urea-water solution to be injected into the exhaust system. During pressure control, i.e. during normal operation with metering, the pump is actuated in such a way that a pressure of 5 bar is applied in the metering line. Only a small part of the urea-water solution delivered by the pump is actually injected. The majority of the solution is transferred via a throttle back into the active reservoir. This means, the delivery pressure is determined by the pump speed together with the throttle cross section. Index Explanation Index Explanation 1 Metering line 8 Filter 2 Delivery module 9 Level sensor 3 Pump 10 Filter 4 Reversing valve 11 SCR catalyst 5 Filter 12 Exhaust system 6 Restrictor (throttle) 13 Metering module 7 Pressure sensor The solution is injected four times per second. The guantity is determined by the opening time and stroke of the metering valve. However, the guantity is so low that there is no noticeable drop in pressure in the metering line. Evacuating After turning off the engine, the reversing valve switches to reverse the delivery direction of the pump, thus evacuating the metering line and metering module. Evacuation also takes place if the system has to be shut down due to a fault or if the minimum temperature in the active reservoir can no longer be maintained. This is necessary to ensure no urea-water solution remains in the metering line or metering module as it can freeze. The metering valve is opened during evacuation. Advanced Diesel Technology 103 104 Advanced Diesel Technology Level Measurement There are level sensors both in the active as well as in the passive reservoir. However, these sensors are not continuous sensors as in the fuel system for example. They can determine only a specific point, to which a defined quantity of urea-water solution in the reservoir is assigned. Two separate level sensors are fitted in the passive reservoir, one for "full" and one for "empty". The signals from the level sensors are not sent directly to the DDE but rather to an evaluator. The active reservoir contains one level sensor that has various measuring points: • Full • Warning • Empty. Also in this case, there is an evaluator installed between the sensors and the DDE, which fulfils the same tasks as for the pas¬ sive reservoir. Index Explanation 1 Measuring point “full” 2 Measuring point “warning” 3 Measuring point “empty” 4 Reference 5 Level 0 0 2 0 0 This evaluator sends a plausible level signal to the DDE. It recog¬ nizes changes in the fill level caused, for example, by driving uphill/downhill or sloshing of the liquid as opposed to an actual change in the liquid level in the reservoir. Low level is therefore signalled when the corresponding sensor is no longer covered by the urea-water solution for a defined period of time. Once the level drops below this value, it can no longer be reached during normal operation. This means, the liquid sloshing on the sensor or driving uphill/downhill is no longer interpreted as a higher liquid level. Level of urea-water solution Level signal Level > Full Full Full > Level > Warning OK Warning > Level > Empty Warning Empty > Level Empty The level measurement system must also recognize when the active and passive reservoirs are refilled. This is achieved by comparing the current level with the value last stored. The level sensor signal after refilling corresponds to the signal while driving uphill. To avoid possible confusion, the refilling recog¬ nition function is limited to a certain period of time after starting the engine and driving off - as it can be assumed that refilling will only take place while the vehicle is stationary. A certain vehicle speed must be exceeded to ensure that sloshing occurs, thus providing a clear indication that the system has been refilled. Refilling the system while the engine is running can also be detect¬ ed but with modified logic. The signals sent by the sensors while the vehicle is stationary are also used for this purpose. The vehicle must be stationary for a defined minimum period in order to make the filling plausible. When the urea-water solution is frozen, a level sensor will show the same value as when it is not wetted/covered by the solution. A frozen reservoir is therefore shown as empty. For this reason, the following sensor signals are used for measuring the level: • Ambient temperature • Temperature in active reservoir • Fleater enable. Level Calculation This function calculates the guantity of urea-water solution remain¬ ing in the active reservoir. The calculation is calibrated together with the level measurement. Every time the level drops below a level sensor the corresponding amount of urea-water solution in the reservoir is stored. The amount of urea-water solution actually injected is then subtracted from this value while the pumped guantity is added. This makes it possible to determine the level more precisely than that would be possible by simple measurement. In addition, the level can still be determined in the event of one of the level sensors failing. Since it is possible that refilling is not recognized, the calculation is continued only until the level ought to drop below the next lower sensor. Example: Once the level drops below the "full" level sensor, for example, from now on the guantity of used and repumped urea-water solution is taken into account and the actual level below "full" calculated. Normally, the level then drops below the next lower level sensor at the same time as determined by the level calculation. An adjust¬ ment takes place at this point and the calculation is restarted. If, however, a guantity of urea-water solution is refilled without it being detected, the actual level will be higher than the calculated level. The level calculation is stopped if it calculates that the level ought to have dropped below the next level sensor but the level sensor is still wetted/covered. Byway of exception, a defective level sensor can cause the calcula¬ tion to continue until the reservoir is empty. Advanced Diesel Technology 105 106 Advanced Diesel Technology SCR System Modes When the ignition is switched on, the SCR control undergoes a logical seguence of modes in the DDE. There are conditions that initiate the change from one mode to the other. The following graphic shows the seguence of modes which are subseguently described. INIT (SCR initialization) The control unit is switched on (terminal 15 ON) and the SCR sys¬ tem is initialized. STANDBY (SCR not active) STANDBY mode is assumed either after initialization or in the case of fault. AFTERRUN mode is assumed if terminal 15 is switched off in this state or a fault occurs. NOPRESSURECONTROL (waiting for enable for pressure control) NOPRESSURECONTROL mode is assumed when no faults occur in the system. In this mode, the system is waiting for the pressure control enable that is provided by the following sensor signals: • Temperature in catalytic converter • Temperature in active reservoir • Ambient temperature • Engine status (engine running). The system also remains in NOPRESSURECONTROL mode fora minimum period of time so that a plausibility check of the pressure sensor can be performed. PRESSURECONTROL mode is assumed once the enable is finally given. STANDBY mode is assumed if terminal 15 is switched off or a fault occurs in NOPRESSURECONTROL mode. PRESSURECONTROL (SCR system running) PRESSURECONTROL mode is the normal operating status of the SCR system and has four submodes. PRESSURECONTROL mode is maintained until terminal 15 is switched off. A change to PRESSUREREDUCTION mode then takes place. A change to PRESSUREREDUCTION mode also takes place if a fault occurs in the system. The four submodes of PRESSURECONTROL are described in the following: • REFILL The delivery module, metering line and the metering module are filled when REFILL mode is assumed. The pump is actu¬ ated and the metering valve opened by a defined value. The fill level is calculated. The mode changes to PRESSUREBUILDUP when the reguired fill level is reached ora defined pressure increase is detected. PRESSUREREDUCTION mode is assumed if terminal 15 is switched off or a fault occurs in the system. • PRESSUREBUILDUP In this mode, the pressure is built up to a certain value. For this purpose, the pump is actuated while the metering valve is closed. If the pressure is built up within a certain time, the system switches to the next mode of METERINGCONTROL. If the reguired pressure built-up is not achieved after the defined period of time has elapsed, a status loop is initiated, and VEN¬ TILATION mode is assumed. If the pressure cannot be built up after a defined number of attempts, the system signals a fault and assumes PRESSUR¬ EREDUCTION mode. PRESSUREREDUCTION mode is also assumed when termi¬ nal 15 is switched off or another fault occurs in the system. VENTILATION If the pressure could not be increased beyond a certain value in PRESSUREBUILDUP mode, it is assumed that there is still air in the pressure line. The metering valve is opened for a defined period of time to allow this air to escape. This status is exited after this time has elapsed and the system returns to PRESSUREBUILDUP mode. The loop between PRESSUREBUILDUP and VENTI¬ LATION varies corresponding to the condition of the reducing agent. The reason for this is that a different level is established after REFILL depending on the ambient conditions. Repeating the ventilation function will ensure that the pressure line is completely filled with reducing agent. PRESSUREREDUC¬ TION mode is assumed if terminal 15 is switched off or a fault occurs in the system. METERINGCONTROL The system can enable metering in METERINGCONTROL mode. This is the actual status during normal operation. The urea-water solution is injected in this mode. In this mode, the pump is actuated in such a way that a defined pressure is established. This pressure is monitored. If the pressure pro¬ gression overshoots or undershoots defined parameters, a fault is detected and the system assumes PRESSURERE¬ DUCTION mode. These faults are reset on return to METER¬ INGCONTROL mode. PRESSUREREDUCTION mode is also assumed if terminal 15 is switched off or another fault occurs in the system. Advanced Diesel Technology 107 108 Advanced Diesel Technology PRESSUREREDUCTION Metering enable is cancelled on entering PRESSUREREDUCTION mode. This status reduces the pressure in the delivery module, metering line and the metering module after PRESSURECONTROL mode. For this purpose, the reversing valve is opened and the pump actu¬ ated at a certain value, the metering valve is closed. PRESSUREREDUCTION mode ends when the pressure drops below a certain value. The system assumes NOPRESSURECON- TROL mode if the pressure threshold is reached (undershot) within a defined time. The system signals a fault if the pressure does not drop below the threshold after a defined time has elapsed. In this case or also in the case of another fault, the system assumes NOPRESSURE- CONTROL mode. NOPRESSURECONTROL mode is also assumed when terminal 15 is switched on. AFTERRUN The system is shut down in AFTERRUN mode. If terminal 15 is switched on again before afterrun has been completed, afterrun is cancelled and STANDBY mode is assumed. If this is not the case the system goes through the submodes of AFTERRUN. • TEMPWAIT (catalytic converter cooling phase) In AFTERRUN mode, TEMPWAIT submode is initially assumed if the system is filled. This is intended to prevent excessively hot exhaust gasses being drawn into the SCR system. The duration of the cooling phase is determined by the exhaust gas temperature. EMPTYING submode is assumed after this time, in which the exhaust system cools down, has elapsed. EMPTYING submode is also assumed if a fault occurs in the system. If terminal 15 is switched on in this sta¬ tus, STANDBY mode is assumed. EMPTYING The system assumes AFTERRUN_EMPTYING submode after the cooling phase. The pressure line and the delivery module are emptied in this submode. The urea-water solution is drawn back into the active reservoir by opening the revers¬ ing valve, actuating the pump and opening the metering valve. This is intended to prevent the urea-water solution freezing in the metering line or the metering module. The level in the metering line is calculated in this mode. PRESSURECOMPENSATION mode is assumed if the meter¬ ing line is empty. PRESSURECOMPENSATION mode is also assumed if a fault occurs in the system. If terminal 15 is switched on, STANDBY mode is assumed. PRESSURECOMPENSATION (intake line - ambient pressure) After the system has been completely emptied, PRES¬ SURECOMPENSATION submode is assumed. In this status the pump is switched off, the reversing valve is then closed followed by the metering valve after a delay. The time interval between switching off the pump and closing the valve prevents a vacuum forming in the intake line; pressure com¬ pensation between the intake line and ambient pressure takes place. After executing the steps correctly the system assumes WAIT- ING_FOR_SHUTOFF submode. WAITING_FOR_SHUTOFF is also assumed if a fault occurs in the system. If terminal 15 is switched on, STANDBY mode is assumed. WAITING_FOR_SHUTOFF (shutting down SCR) The control unit is shut down and switched off. Advanced Diesel Technology 109 110 Advanced Diesel Technology Warning and Shut-down Scenario The SCR system is relevant to the vehicle complying with the exhaust emission regulations - it is a prereguisite for EPA approval. If the system fails, the approval will be invalidated and the vehicle must no longer be operated. Avery plausible case leading to the system failure is that the urea-water solution runs out. Vehicle operation is no longer permitted without the urea-water solution, therefore, the engine will no longer start. To ensure the driver is not caught out, a warning and shut-down scenario is provided that begins at a sufficiently long time before the vehicle actually shuts down so that the driver can either conveniently top up the urea-water solution himself or have it topped up. Warning Scenario The warning scenario begins when the level drops below the "Warning" level sensor in the active reservoir. At this point, the active reser¬ voir is still approximately 50% full with urea-water solution. The level is then determined as a defined volume (depending on type of vehi¬ cle). From this point on, the actual consumption of the urea-water solution is subtracted from this value. The mileage is recorded when the amount of 2500 ml is reached. A countdown from 1000 mis now takes place irrespective of the actual consumption of the urea-water solution. The driver receives a priority 2 (yellow) check control message showing the remaining range. If the vehicle is eguipped with an on-board computer (CID - Central Information Display), instruction will also be displayed. The driver receives a priority 1 (red) check control message as from 200 mis. The following messages and indicators will be displayed: NO START IN 994 mis CC message in clus¬ ter, range < 1000 miles 13 <•> * . ^9 Exhaust Fluid Reserve! AAAA Please note the remaining driving range. Refill diesel exhaust fluid as soon as possible. Refer to Owner's Manual. A Exhaust Fluid Reserve! Range: 994 mis. CC message in CID, range < 1000 miles CC message in clus¬ ter, range <200 miles A <•> Exhaust Fluid! Exhaust Fluid at minimum level! If driving range reaches 0 miles (km), engine start will not be possible. Refill diesel exhaust fluid Exhaust Fluid Minimum! Range: 196 mis. CC message in CID, range < 200 miles Shut-down Scenario If the range reaches 0 mis, similar as to in the fuel gauge, three dashes are shown instead of the range. The check control message in the CID changes and shows that the engine can no longer be started. In this case, it will no longer be possible to start the engine if it has been shut down for longer than three minutes. This is intended to allow the driver to move out of a hazardous situation if necessary. If the system is refilled only after engine start has been disabled, the logic of the refill recognition system is changed in this special case, enabling faster refill. Exhaust Fluid Incorrect If the system is filled with an incorrect medium, this will become apparent after several hundred miles (kilometers) later by elevated nitrogen oxide values in the exhaust gas despite adequate injection of the supposed urea-water solution. The system recognizes an incor¬ rect medium when certain limits are exceeded. From this point on, a warning and shut-down scenario is also initiated that allows a remaining range of 200 mis. The exclamation mark in the symbol identifies the fault in the system. In this case, the message in the CID informs the driver to go to the <•> <£> r i CQ O CC message in clus¬ ter, in case of incor¬ rect DEF CC message in CID, in case of incorrect DEF Exhaust Fluid incorrect! Incorrect diesel exhaust fluid added. Please note the remaining driving range! If driving range reaches 0 miles (km), engine start will not be possible. Have the system y A Exhaust Fluid incorrect! Range: 196 mis. nearest workshop. CC message in clus¬ ter, range = 0 miles Refill Exhaust Fluid! Engine start will not be possible! Refill diesel exhaust fluid! Refer to Owner's Manual. A Refill Exhaust Fluid! Range: — mis, CC message in CID, range 0 miles Advanced Diesel Technology 111 112 Advanced Diesel Technology Refilling The active and passive reservoirs can be refilled with urea-water solution either by the service workshop or by the customer himself. The system can be refilled without any problems with the vehicle on an incline of up to 5° in any direction. In this case, 90% of the maximum possible fill is still achieved. The volume of the urea-water solution reservoir is designed such that the range is large enough to cover one oil change interval. This means the "normal" refill takes place as part of the servicing work in the workshop. If, however, the supply of urea-water solution should run low prematurely due to extraordinary driving profile, it is possible to top up a smaller guantity. Refilling in Service Workshop Refilling in the service workshop refers to the routine refill as part of the oil change procedure. This takes place at the latest after: • 13000 mis on the E90, • 11000 mis on the E70 or • one year. In this case, the system must be emptied first in order to remove older urea-water solution. This takes place via the extractor connections in the transfer line. Although a small residual guantity always remains in the reservoirs, it is negligible. Topping Up Any reguired guantity can be topped up if the urea-water solution reserve does not last up to the next oil change. Ideally, this guantity should only be as much as is reguired to reach the next oil change, as the system is then emptied. Diesel Exhaust Fluid The diesel exhaust fluid (DEF) is a urea-water solution which acts as a the carrier for the ammonia that is used to reduce the nitrogen oxides (NO x ) in the exhaust gas. To protect persons and the environment from the effects of ammo¬ nia and to make it more easy to handle for transport and refuelling procedures, it is provided in an agueous urea solution for the SCR process. The recommended urea-water solution must meet certain standards for guality which are set forth in accordance with the DIN 70070/AUS32. The DEF is a high-purity, water-clear, synthetically manufactured solution consisting of 32.5% urea with the balance being water (67.5%). The urea-water solution used must correspond to this standard. Health and Safety It is an agueous solution which poses no special risks. It is not a hazardous substance and it is not a dangerous medium which is readily apparent after reviewing the Material Safety Data (MSDS) sheets. The urea-water solution is not toxic. If small amounts of the product come in contact with the skin while handling the urea-water solu¬ tion it is sufficient to simply rinse it off with ample water. In this way, the possibility of any ill effects on human health are ruled out. The urea-water solution can be broken down by microbes and is therefore easily degradable. The urea-water solution poses a minimum risk to water and soil. Refer to local laws regarding han¬ dling and disposal reguirements. Materials Compatibility Contact of urea-water solution with copper and zinc as well as their alloys and aluminum must be avoided as this leads to corrosion. No problems whatsoever are encountered with stainless steel and most plastics. Storage and Durability To avoid adverse effects on quality due to contamination and high testing expenditure, the urea-water solution should only be handled in storage and filling systems specifically designed for this purpose. In view of the fact that the urea-water solution freezes solid at a temperature of -11 °C and decomposes at an accelerated rate at temperatures above 25°C, the storage and filling systems should be set up in such a way that a temperature range from 30°C to -11°C is ensured. Provided the recommended storage temperature of maximum 25°C is maintained, the urea-water solution meets the require¬ ments stipulated by the standard DIN 70070 for at least 12 months after its manufacture. This period of time is shortened if the recommended storage tem¬ perature is exceeded. The urea-water solution will become solid if cooled to temperatures below -11 °C. When heated up, the frozen urea-water solution becomes liquid again and can be used without any loss in quality. Avoid direct UV radiation. Service Concerns When servicing SCR system components, absolute cleanliness is important. When cleaning any components, particularly those which contain the urea-water solution (DEF), it is important to use only “lint-free” cloths. Any lint can contaminate or clog SCR sys¬ tem components rendering the system inoperative. Advanced Diesel Technology 113 Temperature Conversion Table 114 Advanced Diesel Technology Temperature Conversion Table (Celsius/Fahrenheit) c F c F c F c F c F c F c F c F c F c F c F c F c F c F c F -40 -40 -23 - 9.4 -6 21.2 11 51.8 28 82.4 45 113 62 143.6 79 174.2 96 204.8 113 235.4 130 266 147 296.6 164 327.2 181 357.7 198 388.3 -39 - 38.2 -22 - 7.6 -5 23 12 53.6 29 84.2 46 114.8 63 145.4 80 176 97 206.6 114 237.2 131 267.8 148 298.4 165 329 182 359.5 199 390.1 -38 - 36.4 -21 - 5.8 -4 24.8 13 55.4 30 86 47 116.6 64 147.2 81 177.8 98 208.4 115 239 132 269.6 149 300.2 166 330.8 183 361.3 200 391.9 -37 - 34.6 -20 -4 -4 26.6 14 57.2 31 87.8 48 118.4 65 149 82 179.6 99 210.2 116 240.8 133 271.4 150 302 167 332.6 184 363.1 201 393.7 -36 - 32.8 -19 - 2.2 -2 28.4 15 59 32 89.6 49 120.2 66 150.8 83 181.4 100 212 117 242.6 134 273.2 151 303.8 168 334.4 185 364.9 202 395.5 -35 -31 -18 - 0.4 -1 30.2 16 60.8 33 91.4 50 122 67 152.6 84 183.2 101 213.8 118 244.4 135 275 152 305.6 169 336.2 186 366.7 203 397.3 -34 - 29.2 -17 1.4 0 32 17 62.6 34 93.2 51 123.8 68 154.4 85 185 102 215.6 119 246.2 136 276.8 153 307.4 170 338 187 368.5 204 399.10 -33 - 27.4 -16 3.2 1 33.8 18 64.4 35 95 52 125.6 69 156.2 86 186.8 103 217.4 120 248 137 278.6 154 309.2 171 339.8 188 370.3 205 400.9 -32 - 25.6 -15 5 2 35.6 19 66.2 36 96.8 53 127.4 70 158 87 188.6 104 219.2 121 249.8 138 280.4 155 311 172 341.5 189 372.1 206 402.7 -31 - 23.8 -14 6.8 3 37.4 20 68 37 98.6 54 129.2 71 159.8 88 190.4 105 221 122 251.6 139 282.2 156 312.8 173 343.3 190 373.9 207 404.5 -30 -22 -13 8.6 4 39.2 21 69.8 38 100.4 55 131 72 161.6 89 192.2 106 222.8 123 253.4 140 284 157 314.6 174 345.1 191 375.7 208 406.3 -29 - 20.2 -12 10.4 5 41 22 71.6 39 102.2 56 132.8 73 163.4 90 194 107 224.6 124 255.2 141 285.8 158 316.4 175 346.9 192 377.5 209 408.1 -28 - 18.4 -11 12.2 6 42.8 23 73.4 40 104 57 134.6 74 165.2 91 195.8 108 226.4 125 257 142 287.6 159 318.2 176 348.7 193 379.3 210 409.9 -27 - 16.6 -10 14 7 44.6 24 75.2 41 105.8 58 136.4 75 167 92 197.6 109 228.2 126 258.8 143 289.4 160 320 177 350.5 194 381.1 211 411.7 -26 - 14.8 -9 15.8 8 46.4 25 77 42 107.6 59 138.2 76 168.8 93 199.4 110 230 127 260.6 144 291.2 161 321.8 178 352.3 195 382.9 212 413.5 -25 - 13 -8 17.6 9 48.2 26 78.8 43 109.4 60 140 77 170.6 94 201.2 111 231.8 128 262.4 145 293 162 323.6 179 354.1 196 384.7 213 415.3 -24 - 11.2 -7 19.4 10 50 27 80.6 44 111.2 61 141.8 78 172.4 95 203 112 233.6 129 264.2 146 294.8 163 325.4 180 355.9 197 386.5 214 417.1 Temperature Conversion Table (cont.) Temperature Conversion Table (Celsius/Fahrenheit) c F c F c F c F c F c F c F c F c F c F c F c F c F c F c F 215 419 232 449.6 249 480.2 266 510.8 283 541.4 300 572 317 602.6 334 633.2 351 663.8 368 694.4 385 725 402 755.6 419 786.2 436 816.8 453 847.4 216 420.8 233 451.4 250 482 267 512.6 284 543.2 301 573.8 318 604.4 335 635 352 665.6 369 696.2 386 726.8 403 757.4 420 788 437 818.6 454 849.2 217 422.6 234 453.2 251 483.8 268 514.4 285 545 302 575.6 319 606.2 336 636.8 353 667.4 370 698 387 728.6 404 759.2 421 789.8 438 820.4 455 851 218 424.4 235 455 252 485.6 269 516.2 286 546.8 303 577.4 320 608 337 638.6 354 669.2 371 699.8 388 730.4 405 761 422 791.6 439 822.2 456 852.8 219 426.2 236 456.8 253 487.4 270 518 287 548.6 304 579.2 321 609.8 338 640.4 355 671 372 701.6 389 732.2 406 762.8 423 793.4 440 824 457 854.6 220 428 237 458.6 254 489.2 271 519.8 288 550.4 305 581 322 611.6 339 642.2 356 672.8 373 703.4 390 734 407 764.6 424 795.2 441 825.8 458 856.4 221 429.8 238 460.4 255 491 272 521.6 289 552.2 306 582.8 323 613.4 340 644 357 674.6 374 705.2 391 735.8 408 766.4 425 797 442 827.6 459 858.2 222 431.6 239 462.2 256 492.8 273 523.4 290 554 307 584.6 324 615.2 341 645.8 358 676.4 375 707 392 737.6 409 768.2 426 798.8 443 829.4 460 860 223 433.4 240 464 257 494.6 274 525.2 291 555.8 308 586.4 325 617 342 647.6 359 678.2 376 708.8 393 739.4 410 770 427 800.6 444 831.2 461 861.8 224 435.2 241 465.8 258 496.4 275 527 292 557.6 309 588.2 326 618.8 343 649.4 360 680 377 710.6 394 741.2 411 771.8 428 802.4 445 833 462 863.6 225 437 242 467.6 259 498.2 276 528.8 293 559.4 310 590 327 620.6 344 651.2 361 681.8 378 712.4 395 743 412 773.6 429 804.2 446 834.8 463 865.4 226 438.8 243 469.4 260 500 277 530.6 294 561.2 311 591.8 328 622.4 345 653 362 683.6 379 714.2 396 744.8 413 775.4 430 806 447 836.6 464 867.2 227 440.6 244 471.2 261 501.8 278 532.4 295 563 312 593.6 329 624.2 346 654.8 363 685.4 380 716 397 746.6 414 777.2 431 807.8 448 838.4 465 869 228 442.4 245 473 262 503.6 279 534.2 296 564.8 313 595.4 330 626 347 656.6 364 687.2 381 717.8 398 748.4 415 779 432 809.6 449 840.2 466 870.8 229 444.2 246 474.8 263 505.4 280 536 297 566.6 314 597.20 331 627.8 348 658.4 365 689 382 719.6 399 750.2 416 780.8 433 811.4 450 842 467 872.6 230 446 247 476.6 264 507.2 281 537.8 298 568.4 315 599 332 629.6 349 660.2 366 690.8 383 721.4 400 752 417 782.6 434 813.2 451 843.8 468 874.4 231 447.8 248 478.4 265 509 282 539.6 299 570.2 316 600.8 333 631.4 350 662 367 692.6 384 723.2 401 753.8 418 784.4 435 815 452 845.6 469 876.2 Advanced Diesel Technology 115 116 Advanced Diesel Technology Diesel Auxiliary Systems Glow-plug System The glow-plug system is responsible for providing reliable cold start properties and smooth operation when the engine is cold. The DDE control module sends the temperature requirement of the heater plug to the heating control unit. The heating control unit implements the request and actuates the heater plugs with a pulse-width modulated signal. The heating control unit additionally sends diagnosis and status information via the LIN-bus connection back to the digital diesel electronics. Index Explanation Index Explanation 1 Glow plugs 2 Glow plug control module 3 4 5 6 7 8 Index Explanation 1 DDE 2 GSG 3-8 Glow plugs (Cylinders 1-6) The LIN-bus is a bi-directional data interface that operates in accordance with the master/slave principle. The DDE control unit is the master. Each of the six heating circuits can be diagnosed individually. When the heating control unit is switched on for the first time, the electrical resistance of the heater plugs is evaluated at the start of the heating process. A hot heater plug has a much higher resist¬ ance than a cold plug. If hot heater plugs are detected based on their resistance, less power is applied to the heater plugs at the start of the heating cycle. If, on the other hand, cold heater plugs are detected, the maximum power is applied to the heater plugs at the start of the heating cycle. This function is known as dynamic repeat heating. This function avoids the situation where too much power is applied to a heater plug, which is already hot, as the result of a second heating cycle following shortly after the first, and therefore overheats. The DDE control unit determines the necessary heater plug temperature as a function of the following operating values: • Engine speed • Intake air temperature • Injected guantity • Ambient pressure • System voltage • Status signal, starter enable. The digital diesel electronics sends the reguired heater plug temperature to the heating control unit to activate heating. The heating system assumes various operating modes that are explained in the following. Preheating Preheating is activated after terminal 15 has been switched on. The heater system indicator in the instrument cluster is activated at a coolant temperature of < 10°C. Preheating is finished when: • The engine speed threshold of 42 rpm is exceeded (starter is operated) or • the preheating time has elapsed. The preheating time is dependent on the coolant temperature and is defined in a characteristic curve. Coolant temperature in °C Preheating time in seconds <-35 3.5 -25 2.8 -20 2.8 -5 2.1 0 1.6 5 1.1 30 1.1 >30 0 Start Standby Heating Start standby heating is activated when the preheating process is terminated by the preheating time elapsing. Start standby heating is terminated: • After 10 seconds or • when the engine speed threshold of 42 rpm is exceeded. Start Heating Start heating is activated during every engine start procedure when the coolant temperature is below 75°C. Start heating begins after the engine speed threshold of 42 rpm has been exceeded. Start heating is terminated: • After the maximum start heating time of 60 seconds has elapsed or • after the engine start operation has been completed or • when the coolant temperature of 75°C is exceeded. Advanced Diesel Technology 117 118 Advanced Diesel Technology Emergency Heating Emergency heating is triggered for 3 minutes in the event of communication between the DDE control unit and heating control unit failing for more than 1 second. The heating control unit then uses safe values so as to prevent damage to the heating system. Concealed Heating Preheating and start standby heating are activated as so-called concealed heating up to a coolant temperature of 30°C. Concealed heating is triggered a maximum of 4 times and is then not enabled again before the engine is restarted. Concealed heating is triggered by the following signals: • Driver's seat occupancy • Driver's seat belt buckle • Valid key • Terminal R • Clutch operated. Partial Load Heating Partial load heating can occur at coolant temperatures below 75°C after starting the engine. Actuation of the heater plugs depends on the engine speed and load, thus improving the exhaust gas charac¬ teristics. Actuation and Fault Detection The power output stages for heater plug actuation are located in the heater control unit. The heater control unit does not have its own fault code memory. Faults in the heating system detected by the heater control unit are signalled via the LIN-bus to the digital diesel electronics. The corresponding fault codes are then stored in the DDE fault code memory. To avoid damage, the heater control unit shuts down all heating activities when the permissible operating temperature of the heater control unit is exceeded. The ceramic heater plugs are designed for an operating voltage of 7.0 to 10.0 V. A voltage of 10 V can be applied to heat up the plug at a faster rate during the heating process. A PWM signal is applied to the heater plugs for the purpose of maintaining the heater plug temperature. Conseguently, an effective voltage is established at the heater plugs that is lower than the system voltage. Note: The ceramic heater plugs are susceptible to impact and bending loads. Heater plugs that have been dropped may be damaged. Note: A maximum voltage of 7 V may be applied to the heater plugs when removed. Higher voltages without cooling air movement can irreparably damage the heater plugs. Advanced Diesel Technology 119