ASC Sub-Function: Understeer

Understeer occurs when the driver wishes to turn a corner, but despite the front wheels being turned in the direction of the curve, the vehicle continues its forward track. This occurs when the front wheels no longer have sufficient lateral locating force (traction).

The DSC III can identify the situation and initiate a corrective action based on engine torque reduction followed by a controlled brake intervention sequence if needed.

Engine torque reduction is carried out by the DME from a request by the DSC via the CAN bus. The DME sends the torque reduction confirmation back to the DSC.

Brake intervention is carried out by the DSC III hydraulic unit if the driver is not actively braking. An example of a brake intervention at the inside rear wheel is as follows:

• All Inlet Valves are closed except for the right rear inlet.
• Intake Valve for rear circuit is opened.
• Both Changeover Valves are closed.
• Return pump operated.
  Fig 1: Example Of Understeer Correction With DSC III 5.7

  Courtesy of BMW OF NORTH AMERICA, INC.

Just as an ASC regulation, DSC brake intervention carries out:

• Pressure Build
• Pressure Hold
• Pressure release
  Fig 2: DSC III 5.7 Hydraulic Unit Circuit Diagram

  Courtesy of BMW OF NORTH AMERICA, INC.