Traction Control/ESP, engine torque limitation

Fig 1: Identifying Traction Control/ESP, Engine Torque Limitation Graph

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Cars with certain engine variants can be equipped with Traction Control in the TC/ABS/ESP control module. The TCS function in the TC/ABS/ESP control module works both by reducing engine torque (request to Trionic) and applying the brakes on the driving wheels. The rear wheel speed is used as a reference to compare both driving wheels individually. Wheel spin occurs when one of the driving wheels rotates faster than the rear wheels.

TC/ABS receives 2 bus messages from Trionic T7:

• Engine torque 

  The value of the bus message "Engine torque" can vary between -100 Nm and 400 Nm.

  TC/ABS/ESP uses the engine torque value to calculate the current driving wheel torque.

• Pedal position 

  TC/ABS/ESP uses the value to determine how much wheel spin to allow.

• Current gear 

  Knowing the engine torque and the current gear ratio, TC/ABS is able to calculate the driving wheel torque.

  TC/ABS/ESP sends one bus message used by Trionic T7:

  Fig 2: Traction Control/ESP, Engine Torque Limitation Circuit Diagram

  Courtesy of SAAB-SCANIA OF AMERICA, INC.
• Requested engine torque 

  The value of this requested torque is used for Traction Control/ESP.

  Trionic T7 converts Nm to mg air/combustion. The value constitutes the maximum air mass/combustion allowed by TC/ABS/ESP.

For further information on Traction Control and TC/ABS/ESP , see TC/ABS 5.3 or TC/ESP .