xDrive
VS-42 je
Baugruppe/Group: 27
weltweit
Datum/Date: 11/2003
27 01 03 (048)
Update: 02/2007
E53, E70, E83
Scheme 39
All-wheel control
Dynamic Stability Control (DSC) specifies the nominal value for xDrive all-wheel control. The nominal value depends on the vehicle's tendency to oversteer or understeer and wheel slip. The nominal value is transmitted to the VTG control unit.
Automatic differential brake
The automatic differential brake (ADB-X) simulates the function of conventional limited-slip differentials by selectively applying brakes on individual wheels (known from the E53 and the E46 All-wheel drive).
Whenever a wheel displays a tendency to spin the ADB-X automatically brakes it down to a preset slip. This effect of this is to increase the drive torque on those wheels that have a higher friction coefficient on a lining.
Hill Descent Control
Hill Decent Control (HDC) is a cruise control on four-wheel drive cars for driving downhill (known from the E53 and the E46 All-wheel drive).
HDC can be activated and deactivated with a separate button.
When the HDC button is pressed, HDC automatically reduces road speed. The brakes are applied on all four wheels to reduce road speed to just above walking pace. HDC holds this speed constant (all DSC functions remain active).
The car's road speed can be freely varied within fixed values by pressing down on the accelerator pedal, brake pedal or the buttons for the cruise-control system.
The following control units and switches are incorporated in xDrive functions
- DME or DDE: Digital engine electronics or digital diesel electronics The DME or DDE modifies the engine response as required by the DSC control unit (such as power reduction to prevent the driven wheels from spinning).
- Instrument cluster display System states are displayed as follows: DSC/xDrive telltale and warning lights light up: DSC/xDrive not activated DSC/xDrive telltale and warning lights light up and acoustic signal: DSC defective, ABS not affected, VTG control unit OK or DSC OK, VTG control unit defective > All-wheel drive in emergency mode DSC/xDrive telltale and warning lights, ABS telltale and warning lights and general brake warning lamp light up and acoustic signal: Total failure of the DSC and/or malfunction of the VTG control unit > All-wheel drive in emergency mode > E53, E83 The instrument cluster is the data interface (= gateway) between the K-bus and the PT-CAN. JBE: Junction box electronics > E70 The JBE is the data interface (= gateway) between the K-CAN and PT-CAN. The junction box comprises the JBE and the power distributor.
System functions
xDrive comprises the following functions
- Control of the locking torque for the multi-plate clutch
- Emergency operation