Operating strategies
Drive wheel slippage

Intervention times in road conditions with good grip (asphalt):
Torque reduction by the engine control unit by altering ignition advance - 6/100 s after the skid threshold is exceeded;
Further torque reduction by reducing throttle opening (by the engine control unit with motorized throttle body) - after 15/100 s. Hydraulic system intervention (braking force on drive wheel) - after 2/10 s.

Operation under conditions of poor grip:
The system is able to detect this situation by comparing drive wheel acceleration with torque transmitted by the engine (engine load via engine control unit).
The system performs in the same way as when both drive wheels are in road conditions with good grip (asphalt) and the cut in thresholds are at the lower limit.

Only one drive wheel slipping:
Torque reduction by the engine control unit by altering ignition advances - 6/100 s after the threshold is exceeded.
Further torque reduction by reducing throttle opening (by the engine control unit with motorized throttle body) - after 15/100 s. Effect on hydraulic system, braking action is exerted on the slipping wheel to give the differential a resistive force on the side with poor grip (T.C.).
This resistive force allows the differential to transmit an equal torque with good grip.

One wheel slipping on a bend with good grip (asphalt):
The system detects the presence of a bend from the rear wheel speed (drawn).
It implements the same intervention procedures described for when only one drive wheel is slipping; the cut-in thresholds are increased to the upper limit. The torque reduction is applied gradually.

One wheel slipping on a bend with poor grip (snow or ice):
It implements the same intervention procedures described for when only one drive wheel is slipping; the cut-in thresholds are increased to the lower limit. The torque reduction is accentuated (to ensure good car lateral containment).


 
Under A.S.R. operating conditions, when the control unit simultaneously receives a signal from the brake light switch, the system ceases to act on the brakes. The torque reduction part remains active.
 
With the brake lights switch activated, but with maximum braking pressure (e.g. tip of heel, defective switch, etc.), if the system detects a speed difference between the front and rear wheels which implies the operation of the A.S.R., only torque reduction is implemented. Brake intervention is excluded.

 




Modulating braking torque with engine decelerating:
Car instability during deceleration with poor grip
The system recognises the condition from engine load, front and rear wheel speed and brake pedal sensor. In this case, drive torque is increased when the engine control unit cuts in to open the motorised throttle. This overcomes the natural instability of the car due to the engine braking torque with poor grip.