Purpose and Benefits (ASR)

General
Acceleration slip regulation (ASR) is an automatic system for improving the starting off and acceleration capability as well as directional stability.

The basic ABS and ASR components are combined in the ASR hydraulic unit.

The ABS and ASR circuits are also combined in the electronic system of the brake control circuit.

Brake Moment Control Circuit
ABS prevents the wheels from locking when braking and therefore maintains the steerability and directional stability when the vehicle decelerates.

ASR prevents the drive wheels spinning while driving. it also improves directional stability with an increased traction capability throughout the entire speed range.

Drive Moment Control Circuit
In the case of the gasoline engine the electronic accelerator (FA) and injection and ignition systems (HFM-SFI, LH-SFI, ME-SFI or MSM and if necessary DI/KSS) are used to control the drive moment control circuit. Engine control using the throttle valve and ignition timing or fuel shut-off is performed by these systems on the gasoline engine. The fuel quantity is controlled by the IFI, DFI or CRD control modules on the diesel engine.

Engine braking regulation (EBR) is also integrated in the ASR (except on the gasoline engine with fuel shut-off). It prevents the drive wheels slipping in overrun mode and ensures directional stability.

The connection between the ASR control modules and the respective control modules of the engine control (LH-SFI, HFM-SFI, ME-SFI, MSM, DFI, IFI, CRD and if necessary LA and DI/KSS) and the transmission control (ETC) is made via a CAN data bus. There is a CAN connection to the instrument cluster as of approx. 06/96.

The switching circuit for the cruise control system (CC) is included in the EA, HFM-SFI/MFI or ME-SFI control module. The drive moment control circuit can be switched off via an ASR off switch (ASR OFF). The brake moment control circuit takes over a function similar to the ETS.

Advantages
^ Improves starting-off and acceleration capabilities through increase traction; particularly advantageous on road surfaces with different adhesion and on corners.
^ Increases the active dynamic safety as only a wheel which is not spinning permits optimum propulsion without loss of lateral control.
^ Automatically adapts the engine torque to the respective transmission capabilities of the wheels to the road, if the driver accelerates too much.
^ A warning lamp in the speedometer signals to the driver that he has approached the physical driving limits of his vehicle, provides information on the ASR control mode and the ASR cut-out,
^ The vehicle stability on the overrun is increased by MSR control.