Table of Contents E70 Chassis Dynamics Workbook Subject Page Chassis And Suspension .7 Front Axle .8 Virtual Pivot Point.9 Front Axle Data .9 Front Axle Adjustments.9 Rear Axle.10 Chassis Comparison (E70 vs. E53) .11 Wheels and Tires.12 RSC tires with emergency running properties .12 Extended Hump Rims (EH2+) .12 Tire Pressure Monitoring System (TPMS).12 Brakes.13 Steering Column .13 Lateral Dynamics .14 Active Steering (AS).14 Changes to Active Steering .15 Cumulative (total) Steering Angle (virtual) .15 Electronically Controlled Bypass Valve (EVV).15 Yaw-rate Control Plus (GRR+).16 Special Feature .16 Difference to Yaw Moment Compensation .16 Initial Print Date: 12/06 Revision Date: Table of Contents Subject Page Vertical Dynamics.18 Adaptive Drive .18 Vertical Dynamics Control.19 Comparison between EDC-K in the E65 and VDC in the E70.20 VDC System Overview .21 VDC Overview Explanation .21 Objectives of the VDC System .22 System Network .22 VDC Components .23 Control Strategy .23 Display Control .24 Degradation Behavior in the Event of a Fault.24 Diagnostic Functions .24 EDC Satellite Control (with damper) .25 EDC Satellite Control Unit.25 Twin-Tube Gas Pressure Damper.26 Ride-height Sensor.26 E70 Ride Height SensorVariants .27 FlexRay in the E70 .28 Bus Topology .29 Line-based Bus Topology.29 Point-to-point Bus Topology.29 Mixed Bus Topology.29 Redundant Data Transmission .29 Bus Topology of FlexRay in the E70.30 Transmission Medium - Signal Properties .30 Deterministic Data Transmission.31 Table of Contents Subject Page Bus Protocol.31 High Bandwidth.31 Synchronization.31 Wake-up and Sleep Characteristics.32 Wiring .32 Active Roll Stabilization .36 Passive vs. Active Roll Bar .36 ARS System Overview (E70).37 ARS System Components.38 ARS Control M odule .38 Lateral Acceleration Sensor .38 Active Anti-roll Bar .39 Hydraulic Valve Block.40 Tandem Pump.41 Radial Piston Pump (part of tandem pump).41 Vane-cell Pump (part of the tandem pump).41 Fluid Reservoir.42 Fluid Level Sensor .42 Hydraulic-fluid Cooler.42 Service Notes.43 Steering Angle Calibration.43 ARS Initialization .43 ARS Bleeding Procedure .43 Programming .43 Coding.43 Electronic Height Control (EHC) .44 EHC Control Unit.45 Table of Contents Subject Page Air Supply Unit (LVA) .45 AirSuspension .45 Ride-height Sensor.45 Longitudinal Dynamics.46 Dynamic Stability Control .46 ABS .46 DSC System Overview.47 Overview of DSC Components.48 DSC Hydraulic Unit.48 DSC Control Unit .48 Wheel Speed Sensor.48 DSC Sensor.48 Steering Column Switch Cluster(SZL).49 Overview of DSC Functions (DSC E7X) .49 Electromechanical Parking Brake (EMF) .50 Basic Functions of EM F .51 Emergency Release.51 Restoring Operation After Emergency Release.51 EMF Components.52 EMF Button .52 EMF Actuating Unit .52 EMF Actuating Unit (Internal Components).53 Service Information for EM F .54 Adjusting the Brake Shoes .54 Removing the Bowden Cable Assemblies.54 Start-up .54 Table of Contents Subject Page Initializing the Parking Brake.55 Bedding in the Duo-servo Brake .55 Function on Brake Rolling Dynamometer .55 Example Scenarios .55 Transition from EMF Actuating Unitto DSC .55 Transition from DSC to EMF Actuating Unit.55 Function of the Parking Brake Controlled by the DSC Hydraulics .56 Dynamic Braking .56 Exiting Dynamic Emergency Braking .57 Error Messages .57 General Parking Brake Fault Concept .58 Fault Distribution Between DSC and EMF Control Unit.58 Fault Regeneration .58 Dynamic Cruise Control (DCC) .59 6 E70 Chassis Dynamics Workbook E70 Chassis Dynamics Model: E70 Production: From Start of Production IBIECTIVES After completion of this module you will be able to: • Identify and Adjust E70 Front Suspension • Diagnose VDC and FlexRay Concerns • Understand Changes to Active Steering on the E70 Chassis And Suspension E70 Chassis Dynamics Workbook 7 8 E70 Chassis Dynamics Workbook Front Axle Forthe first time on a BMW vehicle, a double wishbone front axle is used on the E70. The outstanding driving dynamics, the excellent driving comfort as well as the stable straight-ahead running properties are factors of this design solution that contribute to a high degree of driving pleasure and safety while making the vehicle ideal for every day use and providing the most relaxing drive on long journeys. Index Explanation 1 Ride-height sensor 2 Mount 3 Spring strut 4 Uppercontrol arm (upperwishbone) 5 Spring strut support 6 Swivel bearing 7 Wheel bearing 8 Stabilizer link 9 Tension strut with hydraulic mount 10 Control arm, bottom 11 Spring strut fork 12 Anti-roll bar The addition of the upper control arm (wishbone) positively influences front wheel travel by reducing Camber changes during jounce and rebound events. The arrangement of the suspension allows the strut assembly to be focused on dampening duties alone. The strut is no longer part of the steering, but fixed in place (no upper bearing). The steering axis now rotates by way of the swivel bearing (6). The arrangement of the front suspension includes bearings at various swivel points. This allows for reduced friction, which in turn allows the damper (strut) to respond more sensitively to road surface irregularities. This design works well in conjunction with the Vertical Dynamics M anagement (VDM) system. Components with special materials (see graphic on previous page): • The forged aluminum swivel bearing (6) with the 3rd genera¬ tion wheel bearing (7) Semi-trailing arm connected via steel bushes/tapered screw connection to the swivel bearing. Attention: Referto special repair instructions! • The A-arm at the top (4) is made from forged aluminum and the cylindrical joint pin is clamped in the swivel bearing (6). • Tension strut with hydraulic mount (9) and bottom control arm (10) are forged steel components while the bottom control arm bears the spring strut (3) by means of the cast steel spring strut fork (11). • The front axle subframe is a welded steel structure with an aluminum thrust panel for maximum lateral stiffness with service openings. Virtual Pivot Point The steering pivot axis of the wheel suspension is now formed by a joint at the top A-arm and the virtual pivot point of the lower arm level as known from the spring strut or McPherson axle. Front Axle Data Front axle data E70 Wheel R18 8.5J X 18 EH2 +IS46 Tires 255/55 R18 Rim offset (mm) 46 Tire radius (mm) 338 Wheelbase (mm) 2933 Track width (mm) 1644 Camber -0° 20' ±20' Camber difference 0° ±30' Total toe-in 10' ±6’ Wheel axle angle o O Kingpin offset (mm) -8.4 Toe-out difference angle 2.1° ±30' Caster angle 7° 48' ±30' Front Axle Adjustments The toe adjustment on the front axle is carried out by means of a tie rod adjustment as on past models. The Camber adjustment, however, can only be adjusted by a replacement of the upper control arm (wishbone). The control arm is available in three possible part numbers. One of which is the standard (zero) arm, while the other two are offset to effect a small Camberchange if needed. E70 Chassis Dynamics Workbook 9 10 E70 Chassis Dynamics Workbook Rear Axle The E70 utilizes the integral IV rear axle from the E53 with some further improvements. This rear axle design contributes to improved driving dynamics without compromising comfort and driving safety. The rear axle arrangement made it possible to increase the width and depth of the load area. The result is a considerably larger and more functional load space (third row of seats) particularly through the use of the single-axle air spring (rear axle air suspension). The resulting advantages include: • Outstanding driving dynamics, further increased compared to the E53, without compromising comfort and driving safety. • Distinctly larger and more functional load area by increasing the effective load width and depth. • Level control (1-axis air suspension) ensures constant ride- height and driving characteristics irrespective of the vehicle load. Rear axle data E70 Wheel R18 8.5J X 18 EH2 +IS46 Tires 255/55 R18 Rim offset (mm) 46 Tire radius (mm) 338 Wheelbase (mm) 2933 Track width (mm) 1650 Camber -1° 30' ±15' Camber difference 0° ±30' Total toe-in 10' ±6' Wheel axle angle o O Index Explanation 1 Control arm 2 Wheel carrier 3 Integral link 4 Upper radius arm 5 Swinging arm Chassis Comparison (E70 vs. E53) E53 E70 Front axle Double pivot spring strut front axle Double wishbone front axle Suspension/damping, front Steel spring orairspring Steel spring Anti-roll bar, front M echanical M echanical or Hydraulic Rear axle Integral IV Integral IV Suspension/damping, rear Steel spring orairspring Steel spring orairspring Anti-roll bar, rear M echanical M echanical or Hydraulic Brake, front B rake disc diameter up to 356 mm Brake disc diameter up to 365 mm Brake, rear Brake disc diameter up to 324 mm Brake disc diameter up to 345 mm Parking brake Drum brake, mechanical Drum brake, with electro-mechanical parking brake (EMF) Wheels/tires Standard tires Run flat tires Steering Power steering orServotronic Power steering or active steering E70 Chassis Dynamics Workbook 11 12 E70 Chassis Dynamics Workbook Wheels and Tires Forthe first time, an X-vehicle is equipped as standard with the run flat safety system. Tire damage and tire failure are among the most feared driving experiences. The BMW run flat safety system: • Warns the driver in good time of imminent tire pressure loss so that counter-measure can be taken. • Allows the journey to be continued for a defined distance even in the event of complete loss of tire pressure. • Keeps the tire safely on the rim even in the event of sudden tire pressure loss at high speed. The entire safety package consists of three components: • RSC tires with emergency running properties • Extended hump rims (EH2+) • Tire Pressure Monitoring System (TPMS). RSC tires with emergency running properties With its reinforced side walls, additional strip inserts and heat- resistant rubber mixtures, even when completely depressurized, the "self-supporting tire" makes it possible to continue the journey for a limited distance at a maximum speed of 80 km/h. This means each tire is also its own spare wheel. The maximum range after complete tire pressure loss is: • approximately 250 km at low vehicle load • approximately 150 km at medium vehicle load • approximately 50 km at high vehicle load In the case of slow pressure loss, i.e. representative of approxi¬ mately 80% of all tire failure cases, the remaining range as from the TPMS warning is approximately 2000 km. ABS, ASC and DSC remain fully operational even in the event of complete tire pressure loss. When driving with a run flat tire with no pressure, the optionally available adaptive drive system automatically distributes the vehicle weight overthe remaining wheels so as to relieve the load on the depressurized tire with the aim of achieving the highest possible range for continued operation. Extended Hump Rims (EH2+) The specially shaped rim humps ensure that the RSC tire cannot detach from the rim even in the case of sudden tire pressure loss. This means substantially greater safety particularly when driving at high speed and on winding roads. The system consisting of the run flat tires (RSC), rims with the extended hump (EH2+) contour and the electronic monitoring system (TPMS in USA), renders a spare wheel or space-saver wheel, breakdown kit or vehicle jack unnecessary and this creates more storage space in the luggage compartment while also saving weight. Tire Pressure Monitoring System (TPMS) TPM Control Module Note: For more information on the TPMS system, refer to the reference material in the C hassis Dynamics (ST504) class which is available onTIS or ICP. Brakes In terms of function, an optimized high performance brake system is used on the E70. Floating brake calipers are fitted on the front and rear axle. The brake system in the E70 features the known brake wear monitoring system forthe CBS indicator. Front axle N52B30 US+LA N62B48 US+LA Brake caliper housing GGG (Cast iron) GGG (Cast iron) Brake caliper/piston diameter [mm] 60 60 Brake disc thickness [mm] 30 30 Brake disc diameter [mm] 332 348 Size 17" 18” Rear axle N52B30 US+LA N62B48 US+LA Brake caliper housing Aluminum Aluminum Brake caliper/piston diameter [mm] 44 44 Brake disc thickness [mm] 20 24 Brake disc diameter [mm] 320 345 Size 17" 18” Parking brake Duo-Servo 185x30 (EMF) Steering Column The E70 is available with an electrically adjustable steering column as standard equipment. Adjustment range of electrical steering column: • Vertical +/-25 mm • Horizontal +/-20 mm A special feature of the electrically adjustable column is that only one electric motor is required forthe height and tilt adjustment and this motor is connected to a special gear mechanism for both adjustment axes. E70 Chassis Dynamics Workbook 13 14 E70 Chassis Dynamics Workbook Lateral Dynamics Active Steering on the E70 is part of the lateral dynamics systems Nowadays, dynamic driving systems are subdivided according to their mode of operation. For example, lateral dynamics systems are those systems which influence the vehicle laterally (in a turn). In the E70, there are two systems which are considered part of the lateral dynamics systems. • Servotronic - Speed-dependent hydraulic steering torque assistance • AS - Active Steering (previously AFS, Active Front Steering) The E70 is the first all-wheel-drive vehicle to be offered with Active Steering (AS) Servotronic is only offered in conjunction with the Active Steering. Active Steering (AS) Active Steering was initially offered in the E60 (5 Series). Since then, a large proportion of BMW's in the 3 and 6 Series now have Active Steering. It is only the X models and other all-wheel-drive vehicles that have not yet been provided with this for reasons of space. This innovative steering system is now being offered, as an option, in an all-wheel-drive vehicle forthe first time at BMW, namely in the E70. Forthe most part, the active steering system on the E70 is much the same as on previous models. There are some minor changes which will be discussed in this section. Index Explanation Index Explanation 1 DSC Sensor 5 Fluid reservoir 2 Steering Column Switch Cluster 6 Steering gear 3 AS control unit 7 Hydraulic pump 4 AS actuating unit 8 Power steering cooler C hanges to Active Steering 1 On the E70, certain changes have been made to the Active Steering system on the E70. They are as follows: • The cumulative (total) steering angle sensor has been omitted • The ECO valve has been replaced by the Electronically Controlled Bypass Valve (EVV). • Yaw moment compensation is now enhanced with the addition of GRR+. Cumulative (total) Steering Angle (virtual) With the addition of Active Steering on the E70, the total steering angle sensor has been omitted from the system. The value forthe total steering angle is now a "virtual" value which is calculated from the driver's steering angle and the motor position sensor value. The virtual (total) steering angle value provides the same informa¬ tion as the the total steering angle sensor. The initialization proce¬ dure still needs to be carried out when there are any changes to the system. Index Explanation Index Explanation 1 Rack and pinion unit 5 Engine 2 Steering valve 6 EVV 3 Flow regulating piston (in pump) 7 Throttle (restrictor) 4 Vane-cell pump The initialization process has changed and differs slightly from the procedure on previous vehicles with Active Steering. Electronically Controlled Bypass Valve (EVV) The EVV regulates the volumetric flow of hydraulic fluid in the hydraulic pump to ensure that only the volumetric flow currently required to provide power assistance is made available. Example: When the vehicle is being driven straight ahead without power assistance, the circulation pressure in the steering hydraulic circuit drops, thus reducing the circulation pressure and the power con¬ sumption. If a steering movement is required, the volumetric flow is immediately raised again and the usual steering angle speed is ensured. The EVV (1) therefore controls the power consumption of the hydraulic pump, thus reducing the fuel consumption and the C02 emissions ofthe combustion engine. E70 Chassis Dynamics Workbook 15 16 E70 Chassis Dynamics Workbook Yaw-rate Control Plus (GRR+) The "yaw-rate control plus" function assists the driver when he is braking on roads with varying friction coefficients, in a similar way to the yaw moment compensation. This function represents a signifi¬ cant safety feature. In the case of braking on different surface friction coefficients (asphalt/ice orsnow), a moment builds up about the z or vertical axis (yaw moment) rendering the vehicle unstable. In this special case, the Active Steering control unit calculates the steering angle (maximum ±4°) required for the front wheels to keep the vehicle stable using the actual yaw rate and the longitudinal and lateral acceleration. Special Feature This function shortens the braking distance because the yaw-rate control plus allows higher braking pressure on the high friction coefficient side. Difference to Yaw Moment Compensation With yaw moment compensation, an important calculation principle for automatic early counter-steering was the difference between the front wheel braking pressures that were detected by the DSC and based on which the DSC calculated the angle for attack of the front wheels and transmitted to the AS control unit. This shared functionality of the DSC and AS control unit is now fully integrated into the AS control unit with yaw-rate control plus This active counter-steering creates counter-torque about the z or an d, due to the high communication rate, precise interaction vertical axis (red arrow) which compensates for the earlier acting between the two units has now been achieved, yawing force (yellow arrow). In this way, the vehicle is stabilized by clever interaction between the DSC braking and the AS function, resulting in a new safety aspect, unique in this class. Workshop Exercise - Active Steering Using an instructor designated E70, connect the diagnostic equipment and perform a short test. Proceed to test module for Active Steering initialization. Are there any special tools required forthis process? When does this procedure need to be carried out? How is total steering angle value calculated? Is there a "physical" sensorforthe total steering angle? Where can the "startup/adjustment" test module be found in diagnosis? E70 Chassis Dynamics Workbook 17 18 E70 Chassis Dynamics Workbook Vertical Dynamics The vertical dynamics systems are those systems which affect vehicle motion along the vertical (orz-axis). In other words, the up and down movement of the chassis and or body. On the E70, these systems include: • Vertical Dynamics Control (VDC -previously EDC) • Electronic Height Control (EHC) • Active Roll Stabilization (ARS) Adaptive Drive Adaptive Drive is an optional system on the E70 which includes the combination of ARS and VDC. For the first time, these sys¬ tems are functionally linked which provides maximum safety, com¬ fort and agility beyond compare for an S AV. Adaptive Drive reduces lateral roll ofthe body, which normally occurs during high-speed cornering or in the event of rapid swerving. Adaptive Drive also reduces the required steering angle and improves ride comfort coupled with increased driving dynamics. The customer can choose between a normal and a sporty basic setting via a switch on the center console (near G WS). Unpleasant pitching and lateral rolling ofthe body are diminished or eliminated entirely. The self-steering and load transfer charac¬ teristics ofthe vehicle are significantly improved. The reciprocal movements in the upper part ofthe body, which are inherent in the design of SAV vehicles, are considerably reduced. The vehicle can be driven with higher levels of precision and agility. The system also contributes to shorter braking dis¬ tances. Vertical Dynamics Control The Vertical Dynamics Control (VDC) system being introduced on the E70 from SOP. VDC is a component of the Adaptive Drive equip¬ ment package and is an advancement of the EDC-K already fitted on the E65. Like EDC-K, VDC is notable for its continually adjustable dampers whereby, within certain limits, as many damping characteristic curves (damping force - piston speed) as desired can be plotted. The characteristic curve used depends on the driving situation, in otherwords, the variables that describe the dynamic driving state of the vehicle and which are selected automatically at the driver's command. E70 Chassis Dynamics Workbook 19 20 E70 Chassis Dynamics Workbook Comparison between EDC-K in the E65 and VDC in the E70 EDC-K VDC Model E65 from introduction into series production from 7/2001 E70 from SOP 10/06 in the Adaptive Drive equipment package Program Selection via Control Display and controller "SPORT" button next to gear selector switch Control unit EDC-K control unit on the device holder behind glove compartment VDM control unit: rear left of luggage compartment Four EDC satellite control units directly on the damper Sensors Vertical: vertical acceleration sensor, front left, front right, rear right Longitudinal: wheel speed sensors, front left, front right Lateral: steering angle sensor (LWS) from the steering column switch cluster Vertical: fourvertical acceleration sensors integrated in the EDC satellite-control units, four ride-height sensors connected directly to the VDM control unit Longitudinal: wheel speed sensors orvehicle speed from the DSC control unit Lateral: steering angle sensor (LWS) from the steering column switch cluster, Rotor position sensor (if Active Steering fitted), lateral acceleration (DSC sensor) as redundant signal to the steering angle Damper Twin-tube gas-pressure dampers Twin-tube gas-pressure dampers Diagnostics fully compatible VDM and EDC satellite control units flash-programmable Programming EDC-K control unit is flash programmable VDM and EDC satellite control units are flash programmable Coding VDM and EDC satellite control units are codable Malfunction display Messages in the Control Display or instrument cluster M essages in the Control Display or instrument cluster Testing Diagnostic tester Diagnostic tester VDC System Overview Index Explanation Index Explanation 1 J unction Box Control Module 4 Ride height sensors, front 2 Vertical Dynamics Management 5 EDC Satellites 3 Diagnostic connector 6 Ride height sensors, rear VDC Overview Explanation The VDM control module is connected to F-CAN, PT-CAN and the FlexRay bus systems. The four EDC satellites are connected to the VDM through FlexRay. The satellites contain the vertical accelera¬ tion sensors and the solenoid valves for dampening. Each satellite has its own power and ground supply. Power (B+) is supplied bythe KL30g circuit. The ride height sensors are "hardwired" to the VDM and send analog signals to report vehicle ride height. E70 Chassis Dynamics Workbook 21 22 E70 Chassis Dynamics Workbook Objectives oftheVDC System The primary objective of the VDC system to improve ride comfort while maintaining driving safety at an invariably high level. High levels of ride comfort are achieved when the vehicle body hardly moves along the vertical axis in spite of excitations of the vehicle induced by cornering or by the road surface itself (bumps, gaps). Forthis reason, the adjustable dampers are operated in line with a soft, comfortable damping characteristic curve in as many situa¬ tions as possible. High levels of driving safety are achieved if the wheels never lose contact with the road surface and a high support force is available if required. A harderdamping characteristic is therefore set if the driving situation or driver's intervention (e.g. steering, braking) demands it. As with EDC-K, the dampers have an infinite number of damping characteristic curves at their disposal; unlike EDC-K, however, the dampers are controlled not only axle by axle but also at each individual wheel. In its regulation, the system uses the complete characteristic map of the rebound and compression stages between the comfort (1) and stability (2) threshold curves. In the event of a fault, the control range is minimized to safety char¬ acteristic curve (3). System Network The VDC system is a mechatronic system consisting of electronic, hydraulic and mechanical subsystems. These can be subdivided by function as follows: • Detection of input signals - Sensors for ride heights and rates of vertical acceleration to permit detection of the driving state and the prevailing road conditions - Control elementto enable the driverto set the damping program (comfort, sport).This is located on, and electrically integrated in, the gear selector switch. - Steering angle (output by the SZL control unit via F-CAN) for preemptive detection of cornering - Lateral acceleration (out by the DSC sensorvia F-CAN)for detection of cornering - Vehicle speed or wheel speeds (output by the DSC control unit via F-CAN) • Processing unit - VDM control unit - This checks the plausibility of the incoming signals and uses control algorithms that deliver damping forces at individual wheels as a set point value - EDC satellite control units - These process the signals from the vertical acceleration sensors on the one hand and output the processed signal. On the other hand, they convert into a valve current the target force from the VDM control unit by means of a stored characteristic curve • Actuators The electrically controllable valve in the adjusting damper makes it possible to realize the different damping force charac¬ teristic curves • Communications media The VDM control unit is connected to the PT-CAN, F-CAN and FlexRay; the EDC satellite control units are only connect¬ ed to the FlexRay VDC Components VDM Control Unit Index Explanation Index Explanation 1 Comfort Access 4 Vertical Dynamics Management 2 Not for US Market 5 Electronic Height Control 3 Park Distance Control Control Strategy The underlying control strategy is known as the "Skyhook regula¬ tor"; the name reflects the highest of control objectives: to keep the vehicle body at the same height irrespective of the driving situation (as if the vehicle were suspended from the sky). To achieve this highest of all comfort objectives, the movements of the entire body have to be evaluated. To this end, there is a comprehensive analysis of ride heights and accelerations along the z-axis within the frequency range of between approximately 1 and 3 Hz. The necessary (total) damping force forthis control component will turn out to be comparatively low. To simultaneously ensure that the wheels do not lose contact with the road surface and that optimum contact force is transferred according to the situation, the move¬ ment of each individual wheel is evaluated and not just the move¬ ment of the entire body. The movements, or excitations, relevant here take place within a frequency range of between approximately 11 and 13 Hz and can therefore be distinguished from the movements of the body. This control component will therefore calculate high damping forces dependent on the vertical movement of the individual wheel. As a matter of principal, these forces may be different at each individual wheel and, forthe first time with VDC, can be implement¬ ed as such. Furthermore, VDC regulation takes into consideration steering inputs (e.g. transition from straight-ahead travel to corner¬ ing) based on the steering angle curve. If VDC detects a rapid increase in the steering angle, the controller infers that the vehicle is entering a bend and can preventively adjust the dampers on the outside of the bend to a harder setting in advance. In this way, VDC is able to support ARS regulation and contributes to a reduction in vehicle rolling movements (of course, this applies also during steady-state circular driving). Moreover, VDC is able to detect the braking applications of the driver based on the brake pressure information supplied by DSC. A high brake pressure normally results in a pitching of the vehicle; VDC counteracts this by adjusting the front dampers to higher damping forces. This also results in an improvement in the front/rear brake force distribution, which in turn reduces the braking distance (by compar¬ ison with a vehicle without VDC). The VDC controller adjusts the basic damping force level in accor¬ dance with the damping program selected by the driver (comfort/sport). E70 Chassis Dynamics Workbook 23 24 E70 Chassis Dynamics Workbook Nevertheless, high damping forces are always applied at individual wheels in critical driving situations, e.g. despite the fact that the comfort program is selected. Once the individual control components have been prioritized, a target damping force is output on the FlexRay for each wheel or damper. In addition, the dampers are prescribed a current value for the steady-state operating point. Display Control The VDM control unit is responsible for evaluating the button on the gear selector leverthat the driver uses to select the damping program. Depending on the damping program selected, the VDM control unit issues a request on the PT-CAN to switch the LED in the button on or off (off = comfort, on = sport). Degradation Behavior in the Event of a Fault Depending on the type of fault present, the VDM control unit decides which of three degradation levels must come into effect. • Level 1: Substitute values If, for example, the steering angle signal is unavailable, different variables will be used as a substitute value for cornering detection. The driver receives no failure message. No fault code memory entry is stored. • Level 2: Constant supply of current. The VDM control unit specifies a constant damping force, which is the same for all four wheels ("medium-hard damping"). This leads to a constant supply of current to the valve in the adjusting dampers. A triggering factorforthis degradation level may be a faulty ride-height sensor, for example. The driver receives a failure message. A fault code memory entry is stored. • Level 3: Zero supply of current. If a fault is present in the load circuit, e.g. in the control of a valve, the VDM control unit will select the third degradation level: it tells the dampers that the valve is no longer permitted to be supplied with current. The valve therefore moves into a position that corresponds to a rather hard suspension setting. The driver receives a failure message. A fault code memory entry is stored. From the damping force selected in the degradation levels, it can be seen that it is always the safe condition (hardertuning) that is adopted in the event of a fault (failsafe behavior). Diagnostic Functions The VDM control unit only stores its own faults in its fault memory. Faults with the EDC satellite control units are stored in their own fault memory. In the event of a VDC fault, therefore, it is necessary to check not only the fault memory of the VDM control unit, but of the satellites too. The VDM control unit also functions as a diag¬ nostics gateway between the PT-CAN and VD-F lexRay so that the EDC satellite control units are accessible to the tester). Note: The fault memories of the VDM control unit and the EDC satellite control units must be checked in the event of a VDC system failure. Unlike the EDC-Kin the E65, it is not necessary to perform straight-ahead calibration of the VDC system following replacement of the steering angle sensor. EDC Satellite Control (with damper) This new generation EDC on the E70 is located externally, unlike the EDC system in the E65. The twin-tube gas-pressure damper, EDC satellite control unit and the EDC control valve with wiring as far as the first plug connection form one complete component and can only be replaced in this combination. EDC Satellite Control Unit The following functions are implemented in the EDC satellite control unit: • Signal processing:The EDC satellite control units each have one single-axis acceleration sensor on the control unit board. It is a micro mechanical structural element, which converts accelerations into capacitance changes first and then into an analog voltage signal. This is processed accordingly by the EDC satellite control unit and made available to the VDM control unit via FlexRay. • Actuating functions: Each EDC satellite control unit has a damping characteristic map valid forthis type of damperthat is electronically stored in the form of support points. It is therefore possible to compensate for unavoidable toler¬ ances (variations) arising from manufacture and achieve a higher degree of actuating precision (damping force). Note: The EDC satellite control unit with twin tube gas-pressure damper and EDC control valve can only be replaced as one unit. The vehicle model and installation location (e.g. front left) must be stated when a replacement part is being ordered. • Diagnostic functions Each EDC satellite control unit is compatible with diagnostics and has its own fault memory. Index Explanation Index Explanation 1 Strut damper (shock) 3 EDC solenoid (control valve) 2 EDC Satellite (with sensor) Note: The fault memories of the VDM control unit and the EDC satellite control units must be checked in the event of a VDC system failure. If the EDC satellite control units do not respond to diagnostics, there may be a fault in the VDM control unit (diagnostic gateway) or FlexRay. A cali¬ bration of the ride-height sensors and acceleration sen¬ sors must be carried out in the VDM control unit following replacement of an EDC satellite control unit. E70 Chassis Dynamics Workbook 25 26 E70 Chassis Dynamics Workbook Twin-Tube Gas Pressure Damper Index Explanation Index Explanation 1 Damping Force (N) A Control current = 2 A 2 Piston Speed (m/s) B Control current = 0.65 A Ride-height Sensor The ride-height sensors are electrically connected (hardwired) directly to the VDM control unit. The ride height is sent from the sensorto the VDM via an analog circuit. Two way or one-way sensors may be fitted to the rear axle, depending on the vehicle's equipment level. Note: If a new ride- height sensor is being fitted, it must be ensured that only parts with matching part numbers are fitted. In particular, care must be taken not to confuse one-way and two-way sensors (one¬ way/two-way depends on the equipment level of the vehicle). Two-way sensors bearthe marking "dop- pelt" on the housing. E70 Ride HeightSensors Index Explanation Index Explanation 1 One-way ride height sensor with one output B Adaptive drive w or w/o Xenon A Option- Xenon only C Option - EHC only Two-way sensors deliverthe signal not only to the VDM control unit but also to the EHC control unit. E70 Ride Height Sensors (cont.) © ■ E70 Ride Height SensorVariants Index Explanation Index Explanation 1 One-way ride height sensor with one output B Option -EHC and Xenon 2 Two-way ride height sensor with two outputs C Adaptive drive and EHC w or w/o Xenon Index Explanation Index Explanation 1 Two-way ride height sensor with two outputs 2 One-way ride height sensor with one output E70 Chassis Dynamics Workbook 27 28 E70 Chassis Dynamics Workbook FlexRay in the E70 With the launch of the E70, the FlexRay bus system will be used forthe first time worldwide in a standard production vehicle. Currently, the E70 only uses the FlexRay bus in the Vertical Dynamics M anagement (VDM)system. The FlexRay bus system establishes the connection between the VDM control unit (vertical dynamics management) and the EDC satellites at the shock absorbers. Future BMW modules will expand the use of FlexRay due to the need for increased network speed and reliability. The FlexRay bus system in the E70 is designed as a two-wire, sin¬ gle-channel bus system. Acting as the gateway, the VDM control unit establishes the connection between the PT-CAN and FlexRay bus systems. Data communication between the EDC satellites on the FlexRay and the other control units installed in the E70 takes place via the VDM control unit. Index Explanation EDC SVL EDC Satellite, Front Left EDC SVR EDC Satellite, Front Right EDC SHL EDC Satellite, Rear Left EDC SHR EDC Satellite, Rear Right VDM Vertical Dynamics Management The most important properties of the FlexRay bus system are outlined in the following: • Bus topology • Transmission medium - signal properties • Deterministic data transmission • Bus protocol Bus Topology The FlexRay bus system can be integrated in various topologies and versions in the vehicle. The following topologies can be used: • Line-based bus topology • Point-to-point bus topology • M ixed bus topology Line-based Bus Topology All control units (SG1...SG3) in line-based topology are connected by means of a two-wire bus, consisting of two twisted copper cores. This type of connection is also used on the CAN-bus. The same information but with different voltage level is sent on both lines. The transmitted differential signal is immune to interference. The line-based topology is suitable only for electrical data transmission. Point-to-point Bus Topology The satellites (control units SG2...SG5) in point-to-point bus topology are each connected by a separate line to the central master control unit (SGI). Point-to-point topology is suitable for both electrical as well as optical data transmission. Mixed Bus Topology Mixed bus topology caters forthe use of different topologies in one bus system. Parts ofthe bus system are line-based while other parts are point-to-point. Redundant Data Transmission Fault-tolerant systems must ensure continued reliable data trans¬ mission even afterfailure of a bus line. This requirement is realized by way of redundant data transmission on a second data channel. A bus system with redundant data transmission uses two inde¬ pendent channels. Each channel consists of a two-wire connec¬ tion. In the event of one channel failing, the information ofthe defective channel can be transmitted on the intact channel. FlexRay enables the use of mixed topologies also in connection with redundant data transmission. E70 Chassis Dynamics Workbook 29 30 E70 Chassis Dynamics Workbook Bus Topology of FlexRay in the E70 The physical configuration of the FlexRay bus system in the E70 is point-to-point. All EDC satellites are individually connected via plug connections to the VDM control unit. Internally, however, the left and right EDC satellites are connected to form a line-based topology. The two lines are connected by means of a double point-to-point connection consisting of two bus drivers. Every item of information that is sent from one of the EDC satellites orfrom the central VDM control unit reaches all connect¬ ed control units. Index Explanation A Channel 1 B Channel 2 Transmission Medium - Signal Properties The bus signal of the FlexRay must be within defined limits. A good and bad image of the bus signal is depicted below. The elec¬ trical signal must not enterthe inner area neither on the time axis nor on the voltage axis. The FlexRay bus system is a bus system with a high data transmis¬ sion rate and therefore with rapid changes in the voltage level. The voltage level as well as the rise and drop of the voltage (edge steepness) are precisely defined and must be within certain values. There must be no infringements of the marked "fields" (green and red hexagon). Electrical faults resulting from incorrect cable installation, contact resistance etc. can cause data transmission problems. The images shown above can be depicted only with very fast oscilloscopes. The oscilloscope in the current BMW diagnostic system is not suitable for representing such images. The voltage ranges of the FlexRay bus system are: • System ON - no bus communication 2.5 V • High signal - 3.1 V (voltage signal rises by 600 mV) • Low signal - 1.9 V (voltage signal falls by 600 mV) The voltage values are measured with respect to ground. Deterministic Data Transmission The CAN-bus system is an event-controlled bus system. Data are transmitted when an event occurs. In the event of an accumulation of events, delays may occur before further information can be sent. Index Explanation 1 Time-controlled part of cyclic data transmission 2 Event-controlled part of cyclic data transmission 3 Cycle (5 ms total cycle length of which 3 ms static (= time-controlled) and 2 ms dynamic (= event-controlled) n Engine speed < Angle t° Temperature V Road speed xyz.. abc.. Event-controlled information t Time If an item of information cannot be sent successfully and free of errors, this information is continually sent until the communication partner confirms its receipt. If faults occur in the bus system, this "event controlled" information can back up causing the bus system to overload, i.e. there is a significant delay in the transmission of individual signals. This can result in poor control characteristics of individual systems. The FlexRay bus system is a time-controlled bus system that additionally provides the option of transmitting sections ofthe data transmission event-controlled. In the time controlled part, time slots are assigned to certain items of information. One time slot is a defined period of time that is kept free fora specific item of information (e.g. engine speed). Consequently, important periodic information is transmitted at a fixed time interval in the FlexRay bus system so that the system cannot be overloaded. Other less time-critical messages are trans¬ mitted in the event-controlled part. Bus Protocol Deterministic data transmission ensures that each message in the time-controlled part is transmitted in real time. Real time means that the transmission takes place within a defined time. Therefore, important bus messages are not sent too late due to overloading ofthe bus system. If lost due to a temporary problem in the bus system (e.g. EMC problem) a message cannot be sent again. A current value is sent in the next assigned time slot. High Bandwidth The FlexRay bus system operates with a data transmission rate of 10 M bits/s. This speed corresponds to 20 times the data transmis¬ sion rate ofthe PT-CAN. Synchronization A common time base is necessary in orderto ensure synchronous execution of individual functions in interconnected control units. Time matching must take place via the bus system as all control units operate with their own clock generator. The control units measure the time of certain synchronization bits, calculate the mean value and adapt their bus clock to this value. This system ensures that even minimal time differences do not cause transmission errors in the long term. E70 Chassis Dynamics Workbook 31 32 E70 Chassis Dynamics Workbook Wake-up and Sleep Characteristics The control units are activated by means of an additional wake-up line. The wake-up line has the same function as the previous wake-up line (15WUP) in the PT-CAN. The signal curve corresponds to the signal curve of the PT-CAN. As soon as the bus system is woken, the VDM receives a High level on the PT-CAN and transfers this signal to the wake-up line of the FlexRay, thus also waking the satellites. The "wake-up voltage curve" graphic shows the typical behavior of the voltage curve in response to unlocking and starting the vehicle. Phase 1: Driver unlocks the car, the CAS control unit activates the K-CAN and the PT-CAN, the voltage level in the PT-CAN briefly goes to High, the VDM copies the signal and transfers it to the wake-up line on the FlexRay. Phase 2: Car is opened, terminal R is still OFF, the voltage levels in the bus systems drop again. Phase 3: Car is started, terminal 15 is ON, the voltages remain at the set lev¬ els until terminal 15 is turned off again. Phase 4: The complete vehicle network must assume sleep mode at termi¬ nal R OFF in orderto avoid unnecessary power consumption. Each control unit in the network signs off to ensure that all control units "are sleeping". Only when all EDC satellites have signed off at the VDM control unit can this control unit pass on this information to the PT-CAN and therefore to the complete network. An error message is stored if this is notthe case. This error message is then evaluated as part of the energy diagnosis procedure. Wiring The wiring of the FlexRay bus in the E70 is executed as a sheathed, two-core, twisted cable. The sheathing protects the wires from mechanical damage. The terminating resistors are located in the EDC satellites. Each satellite has one terminating resistor. if r (r • | M 41 * >liJ i n TT “ ft ©n J r——— 1 ! r i • i • i * • i • 9 - , xZ ] | 1 1 1 rs* J t KM 075 it frvon 3 MC© 1 a ji _ 2_ an ON a " * Pr*nr !■»*« » 311 03 Since the surge impedance (impedance of high-frequency lines) of the lines depends on external influencing factors, the terminating resistors are precisely matched to the required resistance. The four sections of line to the satellites can be checked relatively easily by means of a resistance measuring instrument (ohmmeter, multimeter). The resistance should be measured from the VDM control unit. See BMW diagnostic system for pin assignments. The following conclusions can be made about the resistance between the VM D module and EDC satellite: • 110 Ohms - There is a break in the line orthe satellite is not connected orthere is a break in the connection to the satellites. E70 Chassis Dynamics Workbook 33 34 E70 Chassis Dynamics Workbook Workshop Exercise - FlexRay and VDM Using the instructor designated E70, connect diagnostic equip¬ ment and perform short test. Note any faults to VDC or EDC systems. List any faults present: Using the test module and or ETM, locate the VDM connector. Unplug the VDM and test resistance to each EDC satellite. Record results below: EDC Satellite Resistance Value Front Left Front Right Rear Left Rear Right While investigating the above fault, note the power supply (B+) to each of the EDC satellites and record in the chart below: EDC Satellite PowerSupply/Fuse # Front Left Front Right Rear Left Rear Right What relay/circuit supplies power supply for each of the above satellites? Besides wiring concerns and terminating resistors, what other issues can affect the FlexRay bus system? What is the operating voltage of the FlexRay bus? What should the resistance values be on a normal (non-faulted) circuit? Are any of the above values out of specification? Can the oscilloscope from the DISplus/GT-1 be used to check the FlexRay bus? Explain answer. E70 Chassis Dynamics Workbook 35 36 E70 Chassis Dynamics Workbook Active Roll Stabilization The customer-friendly name forthe option is "Dynamic Drive" and was first available in the 7 Series with the E65. Since then, the ARS system has been used in the 5 and 6 series and now forthe first time in an SAV - the E70. ARS is one of the two "functionally linked" systems which make up the "Adaptive Drive" feature in the E70. As the vehicle drives through a bend, forces act on the vehicle causing it to rotate about the vehicles roll axis (X-axis). This force causes the body to tilt towards the outside of the bend. Ultimately, this causes the vehicle to rapidly approach its dynamic limits. The ARS system, through the use of active anti-roll bars, is capable of counteracting this force. By preventing this situation, ARS can greatly contribute to vehicle stability especially on turns and during evasive maneuvers. Passive vs. Active Roll Bar The following is a comparison of passive and active roll bars: • Conventional (passive) anti-roll bar - During cornering, the wheel suspension on the outside of the bend is compressed and the wheel suspension on the inside of the bend rebounds. This has a twisting effect on the anti-roll bar (torsion). The forces arising in the bearing points of the anti¬ roll bar produce a moment that counteracts the tilting of the body. The effect is to improve the distribution of loads acting on both wheels on the same axle. A disadvantage of a passive anti-roll bar is that the basic suspension tuning hardens when the suspension is com¬ pressed on one side of the vehicle during straight ahead travel. This results in a reduction in comfort. • Active anti-roll bar- The Dynamic Drive active chassis sys¬ tem also known as Active Roll Stabilization (ARS) - is a revolu¬ tionary step in chassis and suspension engineering. Forthe first time, the trade-off between handling/agility and comfort is largely eliminated. This results in a new type of "driving pleas¬ ure" typical of BMW. Dynamic Drive has two active anti-roll bars, which have a positive influence on body roll and handling characteristics. The fundamental feature of Dynamic Drive is the divided anti¬ roll bars on each axle. The two halves of the anti-roll bars are connected by a hydraulic oscillating motor. One half of the anti-roll bar is connected to the shaft of the oscillating motor, the otherto the housing of the oscillating motor. These active anti-roll bars control stabilizing moments: • which reduce the reciprocal movement of the vehicle body, • which make it possible to achieve high levels of agility and target precision overthe entire road speed range, • and produce optimum self-steering characteristics. During straight-ahead travel, the system improves suspension comfort because the anti-roll bar halves are de-coupled, with the effect that the basic suspension tuning does not additionally hard¬ en when the suspension on one side is compressed. ARS System Overview (E70) y yy y y Index Explanation Index Explanation 1 Hydraulic fluid reservoir 6 Valve block 2 Hydraulic fluid cooler 7 Lateral acceleration sensor 3 Front oscillating motor 8 Hydraulic lines 4 Tandem pump 9 Rear oscillating motor 5 Control unit E70 Chassis Dynamics Workbook 37 38 E70 Chassis Dynamics Workbook ARS System Components The ARS system components are outlined in the following: ARS Control Module The ARS control module (1) is located in the vehicle interior near the right-hand A-pillar. The module is supplied with powervia terminal 30 and is protected by a 10 A fuse. The ARS control module is activated exclusively by the Car Access System (CAS) on a CAN wake-up line after "ignition ON". A vehicle authentication process takes place when the system is started. This compares the vehicle identification numberfrom CAS with the vehicle identification number which is encoded in the ARS control unit. Then the ARS control unit's hardware and software are checked. All the outputs (valve magnets) are subjected to a complex check for short circuits and breaks. If there is a fault, the system switches the actuators into a safe driving condition. The ARS control unit switches off if there is undervoltage or over¬ voltage. The ARS control unit learns the offset forthe steering angle and the lateral acceleration during start-up and during driving. Lateral Acceleration Sensor The lateral acceleration sensor supplies the main sensorsignal. It measures the lateral acceleration of the vehicle during cornering up to a measurement range of 1.1 g. It is installed on the base plate underthe right front seat. The ARS control unit can learn an offset during start-up and when the vehicle is in motion. Active Anti-roll Bar The oscillating motor and the oscillating motor housing are joined by one half of the anti-roll bar. The active anti-roll bar consists of the oscillating motor and the anti-roll bar halves fitted to the oscillating motor, with press-fitted roller bearings fortheir connection to the axle carriers. The use of roller bearings ensures optimum comfort thanks to better response and reduced control forces. V © V -V V © 0 © Index Explanation 1 Anti-roll bar link connection to swivel bearing 2 Anti-roll bar bracket 3 Anti-roll bar 4 Oscillating motor (hydraulic) 5 Anti-roll bar links There are screw plugs in the area of the pressure relief valves on the oscillating motor of the rear-axle anti-roll bar. Rear axle anti-roll bar © Vi) <*) Index Explanation 1 Lines from hydraulic valve block 2 Anti-roll bar links 3 Anti-roll bar 4 Oscillating motor (hydraulic) The rear anti-roll bar is mounted behind the rear axle carrier. The anti-roll bar links are connected to the rear-axle swinging arms. The oscillating motor of the front axle stabilizer bar is fitted with two pressure relief valves. Air filter elements are fitted to the pressure relief valves. These air filter caps with Goretex inserts must not be removed. E70 Chassis Dynamics Workbook 39 40 E70 Chassis Dynamics Workbook Hydraulic Valve Block The hydraulic valve block is located on the floor plate of the vehicle behind the front right hand wheel housing level with the front right hand door. The hydraulic valve block is connected to a carrier plate bolted to the body. ® ® ® © © 3> ^ v2S) & ® © The hydraulic valve block houses the following valves and sensors: • 2 pressure regulating valves; one for the front axle and one for the rear axle • one direction valve • one failsafe valve • 2 pressure sensors; one sensorforthe front axle, one sensor for the rear axle • one switch-position recognition sensor. The hydraulic valve block has the following connections: • 2 lines to the oscillating motor at the front • 2 lines to the oscillating motor at the rear • one connection forthe line to the tandem pump • one connection forthe line to the hydraulic fluid reservoir. Index Explanation Index Explanation 1 Directional valve 8 Tandem pump line 2 Rear-axle pressure sensor 9 Hydraulic fluid reservoir line 3 Line 2, front axle oscillating motor 10 Line 1, rear axle oscillating motor 4 Proportional pressure limiting valve, front axle 11 Line 2, front axle oscillating motor 5 Proportional pressure limiting valve, rear axle 12 Line 1, front axle oscillating motor 6 Front axle pressure sensor 13 Failsafe valve 7 Switch position recognition sensor Tandem Pump The hydraulic pumps fitted in the E70 were developed with a modulardesign. Depending on the engine and equipment specifi¬ cation, a suitably dimensioned hydraulic pump is flange-mounted to the engine in the same installation space. The exact pump design installed is dependent upon the optional equipment, such as: • Basic steering • Active Steering (AS) • CO2 measures • Adaptive Drive • Adaptive Drive and Active Steering. The hydraulic pump driven by the engine's poly-V-belt is, on vehicles with Adaptive Drive, invariably a tandem pump, which con¬ sists of a radial piston part for ARS and a vane-cell partforthe power steering. Radial Piston Pump (partoftandem pump) This radial piston pump has 10 pistons set out in two rows and designed fora maximum pressure of 210 bar. When the engine is idling, the pump speed is approximately 750 rpm. Atthis idling speed, the radial piston part delivers a minimum fluid flow rate of approximately 6.75 liters/minute at a pressure of approximately 5 bar. This means that sufficient system dynamics are also guaranteed when the engine is idling. At a pump speed of 1,450 rpm, the maximum fluid flow rate is limit¬ ed to 13.3 rpm. Vane-cell Pump (part of the tandem pump) This part comprises 10 vane cells and designed fora maximum pressure of 135 bar. The vane-cell part has a characteristic map controlled fluid flow rate of 7-15 liters/minute. The decisive parameters forthe characteristic map are the vehicle's road speed and the steering angle speed. Adaptive Drive and the power steering share the same fluid reservoir and radiator. Index Explanation Index Explanation A Radial piston pump 3 Steering pressure connection B Vane-cell pump 4 ARS pressure connection 1 Intake connection 5 Input flange 2 Proportional valve E70 Chassis Dynamics Workbook 41 42 E70 Chassis Dynamics Workbook Fluid Reservoir In the fluid reservoir is a fluid filter and fluid level sensor. The fluid filter cannot be replaced. The screw cap is fitted with a dipstick, which makes it possible to check the fluid level. A "M AX" mark indicates the maximum permissible fluid level, measured at room temperature (20°C). If a dipstick check at room temperature reveals the fluid reservoirto be dry, the reservoir must be topped up with the specified hydraulic fluid. If the lowest edge of the dipstick is still only just wet with hydraulic fluid (3), this is to be construed as the "M IN" mark. A mobile float contains a reed contact that converts float move¬ ments into an electric signal. The fluid level sensor (1) is fitted to the fluid reservoir. Short/open circuits cannot be detected by the fluid level sensor. A line break is interpreted as a loss of fluid. Hydraulic-fluid Cooler The hydraulic-fluid cooler serves to maintain a fluid temperature of < 120°C in all hydro-mechanical components under all conditions, although temperatures of < 135°C are acceptable for brief periods. Fluid Level Sensor The fluid level sensor detects the fluid level in the fluid reservoir. The fluid level sensor determines whetherthe fluid level has dropped below a critical minimum level and activates a warning message. Normal movements of the fluid in the reservoir are not cause fora message. Service Notes If Dynamic Drive fails, DSC can no longer be deactivated or if it is already deactivated it does not switch back on automatically. The connections for all the hydraulic components are designed in differ¬ ent dimensions and lengths so that they cannot be transposed. A disturbing transmission of noise into the vehicle interior occurs due mainly to the assembly and line connections. The lines must not make contact; they must be routed correctly through the brack¬ ets without slack ortension. They are covered by the underbody paneling. Steering Angle Calibration After work on the front axle, it is necessary to carry out a steering angle calibration with the Dynamic Drive control unit. The Dynamic Drive system is dependent on the exact zero balance of the steering angle. The maximum deviation tolerance is 1. Precise chassis alignment is a prerequisite. The steering angle calibration must always be carried out on the measuring stand and in accordance with BMW axle alignment guidelines. The zero position is lost each time the Dynamic Drive control unit is flash programmed. A steering angle calibration is required when- everthe control unit is flash programmed. ARS Initialization The initialization procedure must always be carried out once the system has been opened ora part has been replaced.This also applies afterthe lateral acceleration sensor has been replaced. The following conditions must be guaranteed for calibration of the offset values ofthe lateral acceleration sensorand the two pressure sensors: • The vehicle must be stand level on all fourwheels • The vehicle must be unladen • The engine must be idling • Rest status (doors closed, persons are not allowed in the vehicle). No persons may remain within the vicinity of moving chassis parts during the initialization (both in the works and the workshop). In addition you must ensure that the basic commissioning conditions (temperature range, constant engine speed etc.) are maintained. The ground clearance must not be limited and the doors must be closed. The arms ofthe hoist may no longer be situated beneath the car. ARS Bleeding Procedure A bleeding procedure must be carried out using the diagnostic tester if the ARS system was opened hydraulically. The bleeding procedure is performed exclusively by way ofthe initialization rou¬ tine ofthe diagnostic tester and not at the pressure relief valves or at the screw plugs ofthe oscillating motors. If the test still detects air in the system, a short movement trip should be made if necessary. The initialization routine must then be repeated afterthe short trip. In the event of an extreme leak or suspected partial function ofthe pressure relief valves (noticeable by rattling noises in the front end), the pressure relief valves and the pneumatic lines must be replaced with new components. Programming It is possible to program the Dynamic Drive control unit. Coding It is possible to code the Dynamic Drive control unit. Note: For more detailed information on ARS intheE70, refer to the reference material onTIS and 1C P. E70 Chassis Dynamics Workbook 43 44 E70 Chassis Dynamics Workbook Electronic Height Control (EHC) As with the previous SAV, the E53, the new X5 has an available single-axle air suspension system. The EHC system is standard on the 4.8is and only available on the 3.0 version as part of the 3rd row seat option. This system operates in a similar mannerto previous EHC systems. The purpose of a level control system is to maintain the height of the vehicle body as close as possible to a predefined level under all load conditions. Through a constant level of the body mainly the driving quality (e.g. camber, toe-in) will remain unaltered in the event of changes in payload. Index Explanation Index Explanation 1 Air cleaner (filter) 6 Ride height sensor, right 2 Retaining plate 7 EHC control unit 3 Air Supply Unit (LVA) 8 Air spring, rear left 4 Pneumatic lines 9 Ride height sensor, left 5 Air spring, rear right EHC Control Unit The EHC control unit is located in a module carrier in the rear of the luggage compartment on the right-hand side. The EHC control unit receives the following signal information: • Vehicle ride height • Load cutout signals • Terminal 15 ON/OFF • Vehicle speed • Lateral acceleration • "Engine running" signal • Hatch status. The EHC control unit decides on a case-by-case basis whether a control operation is required in orderto compensate for changes in load. It is thus possible to optimally adapt the frequency, specified heights, tolerance thresholds and battery load to the relevant situa¬ tion by means of the control operation. The EHC control unit is fully compatible with diagnostics. Air Supply Unit(LVA) The air supply unit is fitted to the underbody of vehicle by a component carrier level with the front right door. Air Suspension The E70 with EHC uses air spring fitted at the rear axle. Take note of the following cautions: Note: When a new air spring is being fitted, care must be taken to ensure that it is not over-stretched. Otherwise, the retaining ring forthe inner pipe could snap off the rubber gaiter, which could result in dam¬ age to the suspension air bag. Forthis reason, the top of the airspring should be secured to the body first, and only then should it be connected to the axle carrier. Ride-height Sensor The ride-height sensors are electrically connected directly to the EHC control unit. The mode of signal transfer is analog. Two-way or one-way sensors may be fitted to the rear axle, depending on the vehicle's equipment level. Two-way sensors deliverthe signal not only to the VDM control unit but also to the EHC control unit. Note: If a new ride- height sensor is being fitted, it must be ensured that only parts with matching part numbers are fitted. In particular, care must be taken notto confuse one-way and two-way sensors (one- way/two-way depends on the equipment level of the vehicle). Two-way sensors bearthe marking "dop- pelt" on the housing. For more information on ride height sensor configu¬ ration, referto the VDC section of this workbook or the reference material onTIS orICP. E70 Chassis Dynamics Workbook 45 46 E70 Chassis Dynamics Workbook Longitudinal Dynamics Systems which affect the forward or rearward dynamics along the "X-axis" is referred to as longitudinal dynamics systems. These systems include various types of braking systems. In the E70, these systems include: • Dynamic Stability Control (DSC) • Anti-lock Braking System (ABS) • Electro-mechanical Parking Brake (EMF) • Dynamic Cruise Control (DCC) Dynamic Stability Control The DSC system utilized on the E70 is referred to as DSC E7x. The system is supplied by Bosch. With its optimized control functions, the new system design makes a significant contribution to increased driving dynamics. Additional functions for active safety and additional comfort have been implemented in the new system.The new system in the E70 offers the following advantages: • Driving Dynamics - DSC mode: Increased driving dynamics and maximum traction. Thanks to more precise and faster control inter¬ ventions, the driver can further extend the boundaries of driving dynamics while retaining vehicle safety. - DTC mode: Compared to DSC mode, Dynamic Traction Control (DTC) allows for increased slip at the drive wheels to provide maximum propulsion when driving off in snow for instance. In addition, the stabilizing interventions cut in later in DTC mode thus allowing a more sport-oriented driving profile. • Active Safety - The additional functions of brake standby, dry braking and fading assistance shorten the stopping distances. - Increased DSC efficiency makes for more effective safety relevant functions. • Comfort - Improved operating comfort (brake interventions are less audible, pedal vibration is drastically reduced) through the use of a 6-piston pump in connection with a new higher- frequency electrical actuation system. - Additional functions such as start-off assistant and park¬ ing brake provide increased driver assistance and com¬ fort. Note: To date, the DSC driving dynamics system on all¬ wheel drive vehicles was referred to with the abbre¬ viation 11 DXC 11 . S ince this lead to confusion with the xDrive, in the future the dynamic stability control system will be known as DSC also on all-wheel drive vehicles. ABS ABS functions in the E70 are identical to those functions in previous models. The pedal pulsations and noise from the solenoid valves and pump are reduced in the E70. This is a result of the high-performance hydraulic unit on the DSC E7X system. DSC System Overview Index Explanation Index Explanation 1 Hydraulic unit with DSC control unit 5 Center Console Switch Cluster (SZM) 2 Wheel speed sensors (4x) 6 Steering Column Switch Cluster(SZL) 3 Master cylinder 7 Gear Selector Lever (GWS) 4 DSC sensor 8 EM F Actuating Unit E70 Chassis Dynamics Workbook 47 48 E70 Chassis Dynamics Workbook Overview of DSC Components DSC Hydraulic Unit With its new pump concept, the hydraulic unit provides a signifi¬ cant improvement in control accuracy. 2x3 pump elements with a diameter of 6.5mm and intake-optimized units operate in the hydraulic unit.This pump concept ensures substantially improved pressure dynamics resulting in lower pedal feedback in ABS mode and higher control quality. Forthe driverthis is noticeable in as far as the pedal pulsation can now only be felt very slightly during ABS braking. There is a pres¬ sure sensor in the hydraulic unit. DSC Control Unit The DSC control unit can be replaced individually. The 47-pin connector connects the DSC control unit to the engine wiring harness. Wheel Speed Sensor 4 active wheel speed sensors are installed in the E70. All 4 sen¬ sors have a direct hardwired connection to the DSC control unit. These active wheel speed sensors facilitate recognition of the direction of rotation, air gap (clearance) and standstill. The DSC control unit receives this information in the form of a PWM signal. DSC Sensor The DSC sensor is located underthe front passenger seat and is available in two variants in the E70: • Vehicle without active steering, DSC sensor (designation M M 3.8), containing a - Transverse acceleration sensor. - Longitudinal acceleration sensor. - Yaw rate sensor in a housing. • Vehicle with active steering, DSC sensor (designation M M 3.2.2), containing. - 2 redundant transverse acceleration sensors. - Longitudinal acceleration sensor. - 2 redundant yaw rate sensors in a housing. Steering Column Switch Cluster(SZL) The Steering Column Switch Cluster (SZL) is carried overfrom the E90 and consists of the following components: • SZL electronics • Steering angle sensor (optical code disc) • Steering column stalk, cruise control • Steering column stalk, direction indicator • Steering column stalk, wiper • Coil spring assembly The steering column switch cluster can only be replaced as a complete unit. The coil spring assembly is fitted on the steering column switch cluster. The spring coil assembly can be removed and replaced individually. Overview of DSC Functions (DSC E7X) Function Can be switched on/off by driver DSC ON DTC DSC OFF DTC ABS EBV CBC MSR ASC ADB-X DSC HDC Dry braking Start assist Braking readiness Fading assistance DBC -DBS -MBS EMF [parking brake] © GRR+ (included in active steering option) RPA CBS Symbols: • = System active X = System with elevated control thresholds © = Can be switched on/off E70 Chassis Dynamics Workbook 49 50 E70 Chassis Dynamics Workbook Electromechanical Parking Brake (EMF) The concept of EM F has been carried overfrom the E65. The system functions in much the same way as the previous design. Most of the differences lie in component location and emergency release procedures. Index Explanation Index Explanation 1 Dynamic Stability Control 4 EMF actuating unit 2 Master Cylinder 5 Emergency release for EM F 3 Gear Selector Lever E70 Chassis Dynamics Workbook 50 Basic Functions of EMF The parking brake (EMF) has two different functions, depending on the operating status of the vehicle. • Parking brake mode - When the engine is running orthe vehicle is rolling, the parking brake acts on the service brake with the aid of the DSC hydraulics. This means the brake units on the front and rear axle are active. Note: After a power failure, it may still not be possible to move the vehicle even after releasing the brake with the emergency release facility. The parking lock of the automatic gearbox may still be engaged. Once released, using the emergency release facility, the parking brake cannot be reactivated manually.The function can be restored only by way of electrical activation. - If the engine is not running and the vehicle is stationary, the electromechanical actuator and its cable assembly ensure the parking brake acts on the duo-servo drum brake on the rear axle. In this case, the vehicle is braked as defined in the control unit. • Dynamic braking Defined retardation is triggered via the DSC system if the parking brake button is pulled up while driving. The decelera¬ tion is monitored by the DSC control functions and takes place for as long as the parking brake button is pulled. Emergency Release A mechanical emergency release facility is provided in orderto be able to release the parking brake in the event of the electro¬ mechanical actuating unit failing or insufficient power supply. CAUTION!!! Secure vehicle to prevent it rolling before operating the emergency release! The release procedure is performed manually with the emergency release cable assembly (2) and the emergency release handle (1) from the vehicle tool kit. The emergency release procedure releas¬ es the duo-servo drum brake by way of mechanical intervention in the actuator of the electromechanical control unit. Restoring Operation After Emergency Release Afterturning on the ignition, push down the EM F operating button and pull up again to activate the parking brake. E70 Chassis Dynamics Workbook 51 52 E70 Chassis Dynamics Workbook EMF Components EMF Button On the E70, the EMF button (1) is located in the center console next to the gear selector lever. The EMF button is based on the function logic of a hand brake. • Pull EMF button (1) up: Parking brake is activated • Press EMF button (1) down: Parking brake is deactivated EMF Actuating Unit The EMF actuating unit is located on the rear axle component carrier. Note: The indicator lamp in the instrument cluster shows the driver when the EMF is activated. EMF Actuating Unit (Internal Components) The EMF actuating unit is sealed watertight and the housing cannot be opened. The EMF actuating unit contains the following main components: • EM F control unit • Electric motor • Spindle gear mechanism Index Explanation Index Explanation 1 EMF Control unit 8 Flexible band 2 Bowden cable, emergency release 9 Force sensor, pc board 3 Bowden cable, rear left 10 Force sensor magnet 4 Lock pin 11 Bowden cable, rear right 5 Actuating piston 12 Electrical connection 6 Spring 13 EMF Control unit 7 Emergency release cable The force sensor in the EMF actuating unit is a very important componentfor operation of the parking brake. With its signals, the force sensor makes it possible forthe EMF control unit to deter¬ mine the actuating force. The actuating force is essential for secur¬ ing the required braking pressure. 8 7 ) 8 , Index Explanation Index Explanation 1 Flook 5 Force sensor pc-board 2 Retaining plate 6 Piston 3 Hall-IC 7 Spring 4 M agnet 8 Lower section of housing The housing of the force sensor consists of two halves. The lower section of the housing (8) is made from pressure diecast aluminum so that it can take up the exerted forces. The upper section of the housing is made of plastic, to which the force sensor pc-board (5) with the Hall-IC (3) is secured. The magnet (4) is fixed to the piston (6). The sensor is located between the left and right bowden cable assembly. During actua¬ tion, the piston (6) moves with the magnet against the spring (7). The travel range of spring compression is measured in accordance with the familiar Hall principle. Since the spring data are defined, the EM F control unit can calculate the applied force from the travel range and the spring data. The force sensor is calibrated at the end of the assembly line. E70 Chassis Dynamics Workbook 53 54 E70 Chassis Dynamics Workbook Service Information for EMF Adjusting the Brake Shoes The procedure for adjusting the parking brake shoes is the same as before: Turn the adjusting screw using a screwdriverthrough the threaded hole in the wheel hub (10 teeth). Removing the Bowden Cable Assemblies Note: The EMF must be set to service mode with the diag¬ nostic tester before performing any maintenance or service procedures (the parking brake cannot be applied, EMF assumes the outermost position). The EMF will not respond to an operating signal until service mode has been deactivated again. Necessary preparation: • To remove emergency release bowden cable assembly in luggage compartment (see Emergency Release). Use pointed pliers to press togetherthe white clip while pressing in the direction of the floor plate. Remove the wheels, brake calipers and brake discs (according to repair instructions) to expose the duo-servo brake shoes. The heat shield must be removed on vehicles with Active Roll Stabilization (ARS) and the ARS anti-roll bar lowered. (It is suf¬ ficient to release the ARS anti-roll bar at the mounting points and to lower it.) Unplug the electrical connectorfrom the EMF actuating unit. • To detach and expose the emergency release bowden cable assembly (Note: Clip fastening behind wheel arch panel). Release spring clip on wheel carrier. Detach nipple of cable assembly from brake show expander and pull the cable out of the wheel carrier. Release the cable assembly from the clip on the rear axle carrier and pull in the direction of the EMF actuat¬ ing unit. • Detach the carrierforthe EMF actuating unitfromthe rear axle carrier and from the EM F actuating unit and pull out. • Screw the union nut on the rear left wheel cable assembly by 5-7 turns (left-hand thread) into the spline shaft of the actuator. Then fit the twist lock (square) of the threaded spindle in the guide in the actuator housing. The sleeve of the cable assem¬ bly must lie flat on the actuator housing before fitting the union nut.Tighten the union nut to 6 Nm. Attach the rear rightwheel cable assembly to the mounting point on the actuator and secure with the clip. Make sure that the cable is firmly fitted. The cable assembly must lie flat on the actuator housing before fitting the union nut.Tighten to 6 Nm. • Reinstallation takes place in the reverse order of removal. F it the new EMF actuating unit, cable assemblies first, in the package space. If it was necessary to slack off the carrierfrom the EM F actuating unit, it must be resecured to the EM F actuating unit and tightened to a torque of 4 ±0.5 Nm.The component carrier must be secured to the rear axle carrierto a torque of 19Nm±15 %. Before securing the cable assemblies to the wheel carrier (tightening torque 8 Nm), check that the brake cables are securely attached in the brake shoe expander otherwise the EM F actuating unit may be damaged as soon as it is operated. Start-up A new EMF actuating unit is always set to "service mode". This mode can be actively reset with the diagnostic tester or it resets itself automatically on exceeding a defined vehicle speed. The actuating unit is now in "standby mode".The EMF actuating unit mustthen be encoded to the vehicle. Initializing the Parking Brake Note: TheEMF must be initialized with the diagnostic tester after replacing the drum brake linings. Bedding in the Duo-servo Brake If the brake shoes of the duo-servo brake are replaced as part of repair or maintenance work, it is necessary to bed in the brake shoes before a sufficient holding effect may be achieved. Also in this case, the special routine must be activated in the EM F with the diagnostic tester. The flashing indicator lamp in the instrument cluster signals that the bedding-in program is ready. The bedding-in program will be aborted and the normal parking brake function resumed if the bedding-in is not started within 30 minutes of program activation or if the ignition is switched off. The bedding-in procedure can also be performed on the roller dynamometer. Function on Brake Rolling Dynamometer The Operation of the E70 parking brake can be tested on the brake rolling dynamometer. As part of the road inspection, the rear axle brake can be tested with the engine running by pulling the EM F button. As part of the road inspection, the rear axle brake can be tested with the engine running by pulling the EM F button. As a result, the EM F actuating unit is applied, the duo-servo brake is applied and the vehicle normally jumps out of the roller of the test rig. Example Scenarios Basic function of the parking brake controlled by the actuating unit Scenario: "Ignition ON", the engine is notyet running and the foot brake is pressed. With the vehicle stationary, the parking brake is released or applied by pulling or pressing the EMF button. The indicator lamp in the instrument cluster either goes out or lights up red. Note: The parking brake can be released only with the foot brake pressed when the engine is running or turned off. The dynamic braking function is triggered if the EMF operating button is pulled while the vehicle is rolling. Transition from EMF Actuating Unit to DSC The system switches overfrom mechanical to hydraulic mode when the engine is started. If the EMF actuating unit was applied at the time, the DSC hydraulics will assume control of the braking force. The EMF actuating unit is not released until the hydraulics are holding the vehicle secure. The indicator lamp remains lit red throughout this process, and the driver is unaware of the transition (the lamp does not even flash). Transition from DSC to EMF Actuating Unit The transition to the EM F actuating unit always takes place on exit¬ ing the hydraulic function at "ignition OFF". If the parking brake was applied, the hydraulics are not released until the EM F actuating unit is applied. The indicatorlamp remains red throughout this transition. E70 Chassis Dynamics Workbook 55 56 E70 Chassis Dynamics Workbook Function of the Parking Brake Controlled by the DSC Hydraulics Scenario: "Engine mnning" The parking brake is applied or released completely by hydraulic means when the EMF operating button is pulled or pressed. Dynamic braking ( hydraulic) is triggered with the vehicle rolling and the button operated atv >3 km/h. The basic functions mainly correspond to the functional scope of a conventional mechanical parking brake. The system switches between "brake applied" and "brake released" with pressure buildup and pressure reduction every time the EMF button is pulled or pressed. The parking brake must be released by pressing the EM F button before starting off. Pulling away against the applied brake pressure results in an increase in pressure and a warning to the driver. Scenario: "At rest" Remove control removed The parking brake enters rest status when the remote control is removed. If the parking brake is applied, the time-delayed red indicator lamp signals this status to the driver. If the EM F actuating unit is released in rest mode, the EM F actuat¬ ing unit is applied when the EM F button is pulled with the vehicle stationary. If the vehicle is in motion, pressing the button will initiate dynamic braking. Note: Always take the remote control with you when leav¬ ing the vehicle otherwise children could release the parking brake. Dynamic Braking Two braking units for brake operation are required by law (previously: foot brake and hand brake) In the E70, the second operating point besides the foot brake is the EM F button on the gear selector lever. The vehicle is braked by the drum brakes at the rear axle if the EMF button is pressed and held at speeds below v = 3 km/h and with the engine switched off. The vehicle is braked at a rate of 3 m/s^ for 0.8 seconds if the EM F button is pressed when the vehicle is in motion. Braking power is then ramped up to 5 m/s^ forthe next 2 seconds. This braking action is retained for as long as the EM F button is pulled. For stability reasons (over-braking - rear axle) the dynamic braking function is also triggered in the rest state in response to the vehicle rolling (engine turned off, ignition OFF) by means of active pressure build-up by the DSC hydraulics together with the DSC function. The brake pressure required is made available as rapidly as possible. The braking action is always monitored bythe DSC con¬ trol function. This ensures vehicle stability while braking. Since all four wheels are braked hydraulically, there is considerably greater deceleration with a minimum of operating effort (EMF button) by comparison with conventional parking brakes.The controlled brakes are therefore able to contribute to improving vehicle safety. For traffic safety reasons, operation of dynamic braking is indicated to the road users behind bythe brake lights coming on. To avoid accidental operation and misuse, the driver is notified of dynamic braking operation by a display message and gong. This function is intended only for use in an emergency and must never be used as a substitute for normal operation of the service brake. The more effective braking solution is used if the parking brake deceleration request is overlapped by the brake pedal being depressed. The DSC control unit decides which deceleration request is to be carried out. Exiting Dynamic Emergency Braking The vehicle will remain hydraulically braked even afterthe EM F button has been released if the vehicle is braked to a halt by dynamic braking. There is a transition to the normal DSC hydraulics function.The hydraulic brake is only released when the EMF button is pressed once more. If the EM F button is pressed while the vehicle is still in motion, the system level prevailing before the emergency dynamic braking was activated is resumed. If the parking brake is released and the vehi¬ cle is coasting, it is possible to activate emergency dynamic braking in any situation (terminal 30,15, R) by pressing the EM F button. Error Messages All fault statuses are detected by the monitoring system and dis¬ played to the driver. The main aim is to avoid safety-critical condi¬ tions forvehicle occupants, the vehicle and its surroundings. A fault can be assigned different priorities depending on the driving situation (vehicle stationary/ in motion, starting/stopping) and the system availability. In addition to the indicator lamp, supplementary instructions may be shown in the control display. To avoid additional damage, faults in the parking brake mechanism, particularly a broken cable in the operating cable assembly and excess load are detected by the force sensor and indicated accord¬ ingly. (See shutdown strategy table). Error messages can no longer be output actively in the event of the EM F control unit failing. In this case, the instrument cluster assumes the control of the cor¬ rect error message on recognizing the absence of the regular EMF telegram via the PT-CAN (alive signal). Shut-down Strategy Fault Availability Back-up System Parking brake (mechanical) v = 0 Dynamic braking (hydraulic) v>0 CAN signal OK OK DSC hydraulics OK NA Service brake + hand brake Actuating mechanism NA OK Park position automatic gearbox EMF control unit NA NA Park position automatic gearbox and service brake and auxiliary brake if necessary E70 Chassis Dynamics Workbook 57 58 E70 Chassis Dynamics Workbook General Parking Brake Fault Concept Fault Distribution Between DSC and EMF Control Unit Only DSC faults that actually affect operation of the parking brake result in shut-down of the hydraulic function. These are mainly faults that result in shut-down of the ABS functionality. They triggerthe transition to manual emergency mode. Dynamic braking is no longer possible unless only CAN faults occur affecting this functionality. • Shut-down level "electromechanical mode" (only EMF actuat¬ ing unit) initiated by following DSC faults - DSC control unit fault - Electrical fault (e.g. wiring harness) - Sensorfault (brake light switch/wheel speed) - actuator fault/hydraulic unit - Bus communication fault • Shut-down level "electrohydraulic mode" (failure of EMF actuating unit) - Force sensorfault - Actuator fault of EM F actuating unit - Error in actuation electronics - Fault in actuating mechanism - Electrical fault • Shut-down level "total shut-down" - EMF control unit or controller fault -EMF button fault - Electrical fault, power supply Note: All fault codes are stored in the control unitin which the monitoring routine was performed.The EMF con¬ trol unit is informed of the fault status of the DSC control unit and vice versa. Fault Regeneration When a fault is detected, the system remains in a safe mode until the end ofthe "ignition ON" cycle, once reached, a shut-down level is not cancelled during the cycle. Dynamic C ruise Control (DC C) The operating and display philosophy on the DCC steering column stalk and in the instrument cluster in the E70 is the same as that in other model series. Functionally, the DCC is integrated in the DSC control unit. The DCC functionality is realized by way of communication with the partner control units of the DSC control unit in the system network such as DM E/DDE, EGS, SZL and instrument cluster. The DCC function can be activated from 30 km/h/19 mph (up to max. 250km/h/155mph) and is deactivated by similar factors as for cruise control: • Brake pedal actuation • Deactivation of DSC • Activation of DTC • Active DSC intervention • Deactivation by the driver • Speed is reduced below 22 km/h • "N" engaged • EM F function activated DCC achieves a deceleration of max. 2.1 m/s 2 and an acceleration of about. 1.7 m/s 2 . The transverse acceleration is variably limited by the Curve Speed Limiter(CLS). The primary emphasis has been placed on comfortable performance in this system configura¬ tion. When cruise control with brake intervention is activated, the brake lights are also activated in accordance with legal requirements in connection with a system related braking operation DCC. Extended functions of the DCC compared to a conventional cruise control system: • Active brake intervention to realize the set speed also when driving downhill • Curve Speed Limiter (CLS) - adaptation of driving speed when cornering (transverse acceleration). This function limits the maximum transverse acceleration depend¬ ent on vehicle speed with the aim of achieving the greatest possi¬ ble agility in DCC mode. Driving on winding country roads in a speed range from > 50 km/h/31mph to < 120 km/h/74mph is controlled with a value of 3.3 - 3.7 m/s 2 . The value can increase up to 4.5 m/s forfast highway bends and slow lane changes at speeds between <50 km/h/31mph and > 120 km/h/74mph. • Comfort Dynamic System (CDS) - this enables a type of "manual throttle mode" on the steering column stalk. • Adapted downhill mode - the overrun fuel cutout and gear down shift are correspondingly adapted. E70 Chassis Dynamics Workbook 59 60 E70 Chassis Dynamics Workbook Classroom Exercise - Review Questions 1. Circle the bus systems below which are directly connected to the VDM? D-CAN PT-CAN K-CAN FlexRay F-CAN MOST LIN BSD 4. On previous vehicles equipped with Active Steering (AS), the ECO valve was responsible for controlling the flow of power steering fluid. Which component replaces the ECO valve in the E70? (circle the correct answer) EWS VDM EVV GRR + GWS SHL ARS RFK 2. Which of the following diagnostic procedures is NOT recommended (or possible) when investigating faults in the FlexRay system? (cross out the procedure which is NOT useful in diagnosis) ETM and Ohm meter Fault codes and test modules Oscilloscope in DISplus orGT-1 Physical inspection of connectors and wiring On an E70 equipped with the Adaptive Drive package and Active Steering a tandem power steering pump is installed. Which part of the power steering pump is responsible for the hydraulic pressure in the ARS system? (circle one) PartA PartB A special tool is used to move the strut assembly The upper wishbone must be replaced The swivel bearing must be replaced ThefrontCambercannotbe corrected in service 5. 3. During an alignment on an E70, a Camberchange is needed, which procedure represents the proper method to change frontCamber? (circle the correct answer) An eccentric must be adjusted 6. On the Active Steering system on the E70, which ofthe (circle one) following components has been omitted as compared to previous models with AS? (circle one) 500Kbit/second 10M bits/second Actuator Motor Sensor 22.5 Mbits/second 10 Kb its/second C umulative (total) steering angle sensor Steering Angle Sensor(SZL) 10. Which ofthe following systems/components on directly connected to the FlexRay bus system? Electromagnetic Safety Lock GWS SZL EDC Satellites EHC VDM EMF 7. On vehicles equipped with VDC, how do the ride height sensors communicate with the VM D control module? (circle one) The sensors are hardwired to the VDM The sensors communicate to VDM via FlexRay The sensors are hardwired to the EDC Satellites The sensors communicate to the VDM via PT-CAN 8. The resistance ofthe terminating resistors on the FlexRay bus is between: (circle one) 200 and 240 Ohms 90 and 110 Ohms 10 and 60 Ohms 80 to 100 Ohms 9. What is the communication speed ofthe FlexRay bus? the E 70 is ARS DME E70 Chassis Dynamics Workbook 61