Principle of Operation
Principle of Operation
DSC
DSC calculates the current driving conditions and corrects detected driving instability through active brake interventions. For example, in the event of vehicle oversteer, DSC initiates brake intervention at the front wheel furthest from the curve to create a stabilizing, opposing torque.
In the event of vehicle understeer, active interventions at the wheels nearest to the curve provide a stabilizing counter torque. DSC stabilization is performed in all driving situations: normal running, acceleration and braking.
The DSC control module is combined with the hydraulic unit and is located on the right front strut tower in the engine compartment.
The DSC function can be deactivated by the Controller in the Control Display menu and the DSC light in the instrument cluster will illuminate to alert the driver. DSC can be reactivated by the Controller or automatically when the ignition is cycled.
Anti-Lock Braking System (ABS)
The ABS system will operate under a full or failsafe state:
- ABS full system: the control module achieves a stabilizing effect on the driver's requests through active brake pressure increase at the individual wheels. Information from the wheel speed sensors, the yaw rate and steering angle sensors determine the vehicle speed. At vehicle speeds <60 km/h an individual control operation matching each situation shortens the braking distance.
- ABS failsafe level: the ABS adopts the failsafe level in the event of a sensor failure or a CAN Bus fault. In this case, the vehicle speed is determined by the wheel speed sensors. In addition, the "select low" control for rear axle stabilization will be applied and the active interventions during brake activation and MSR will be deactivated.
Automatic Stability Control (ASC)
ASC prevents the wheels from spinning during acceleration on all types of road surface. The ASC function is the same as models currently in use.
Engine Drag Torque Control (MSR)
When the accelerator pedal is abruptly released or in the event of unadapted downshifting to a lower gear, the MSR function maintains stability on the rear of the vehicle.
The MSR function is activated at vehicle speeds above 15 km/h to decrease strong load changes through a brief engine torque increase by increasing the Valvetronic lift, advancing the ignition timing, increasing the injected amount of fuel, etc.
Dynamic Brake Control (DBC)
The DBC function is designed to provide the maximum braking force available during rapid (panic) braking situations and includes the following subfunctions.
Dynamic Brake Support (DBS): DBS assists the driver in panic braking situations. This function is triggered by a sufficiently fast actuation of the brake pedal.
The brake pressure generated by the driver is increased by the hydraulic pump to the extent that the front and rear axles go into ABS control mode. The driver can achieve a full deceleration with low pedal force.
Fading Brake Support (FBS): FBS is a new subfunction of DBC that compensates for the brake force loss from an increase in brake temperature. The diminishing braking effect due to hot brakes requires the driver to press the brake pedal more firmly.
This increase in pressure is assumed by an activation of the DSC hydraulic pump. The temperature measurement is a virtual value which is calculated by the DSC control module based on wheel speed, brake pressure, braking time (length) and ambient temperature.
Cornering Brake Control (CBC)
The CBC function is activated in the event of medium to high lateral acceleration. If a vehicle drives into a curve under braking and threatens to oversteer, an increase in stability is achieved through a partial release of the rear wheel brake nearest the curve.
During corner braking, CBC provides the best possible directional stability through optimum brake force distribution. The hydraulic pressure in the rear brake calipers is controlled individually to prevent the vehicle from oversteering.
CBC controls the vehicle prior to ABS or DSC intervention. CBC also operates even when DSC is deactivated and CBC is deactivated in the event of an ABS failure.
Driving Performance Control (FLR)
FLR is a new subfunction of DSC that protects the brakes against overloading (misuse). When a temperature of over 600 °C is determined, the engine power is reduced (max. engine torque 330 Nm) by the ECM. This engine torque reduction is stored as a fault (driving performance control active).
Dynamic Traction Control (DTC)
To improve propulsion, the ASC slip thresholds can be increased up to a speed of 45 mph (70 km/h). The permissible slip is doubled which offers advantages when driving on poor roads and in heavy snow (increased rear wheel spin is permissible).
When chassis dynamics increase as measured by the yaw rate sensor, the slip thresholds are reduced back to the normal mode for stability reasons.
The DTC function can be activated/deactivated by the Controller in the Control Display menu.
When the DTC traction mode is activated, the "DTC" light is illuminated above the DSC safety light (in the instrument cluster).
Parking Brake (Hydraulic Section)
DSC controls the hydraulic function of the Parking Brake. The "Automatic Hold" and "Dynamic Braking" functions affects a hydraulic braking operation on the front and rear service brakes (refer to the E65/E66 Brakes).