Dynamic Stability Control (DSC III)
All of the familiar braking and straight line traction control features and system communication carry over from DSC II. Based on select high/select low logic, the DSC III control module selects a vehicle stabilizing strategy based on the specific input signal values it is monitoring at the moment. For all DSC strategies this begins with engine intervention to reduce torque:
- For the 750iL this is handled via CAN communication, DSC III to EML to minimize the throttle angle of the DK motors (750iL). For the 740i/iL and 540iA this is handled by direct DSC III activation of the ADS II throttle housing.
- If additional torque reduction is necessary, DSC III informs DME over CAN to:
- Retard ignition timing
- Shut down the fuel injection to individual cylinders
DSC III monitors under/oversteer conditions through the following components:
- The driver's desired steering angle - steering angle signal over CAN bus.
- Vehicle speed and speed differential at front wheels - wheel speed sensors
- Dynamic forces of lateral acceleration and yaw placed on the vehicle. This is possible with these two new components. The results are as follows:
The expanded hydraulic control of individual wheel circuits is apparent when stabilizing a vehicle exhibiting an oversteer condition as follows:
Transmission system intervention also occurs during any ASC/DSC regulating phase. Through CAN bus communication the AGS control module is informed to delay any gear changes during regulation. This prevents any unwanted driveline dynamic changes during DSC regulation.
Though DSC III provides state of the art, electronic correction of undesirable vehicle handling characteristics, it is important to remember vehicle stability is always subject to the physical laws of centrifugal force and extreme road conditions. Good judgement and common sense on the part of the driver are still required.