Maximum Permissible Engine Torque

Maximum Permissible Engine Torque





General
The maximum engine torque allowed for the engine is stored as a table in the control module memory. The table specifies the highest torque the engine is allowed to generate at various engine speeds.

Calculation, engine torque
Engine torque is primarily calculated using air mass per combustion and engine speed. But, ignition timing and current lambda value also affect the torque calculation. Retarded ignition timing generates lower engine torque. This is the case in knock control. As regards the lambda value, there is an optimal lambda value for each operating point. If the engine runs richer or leaner than the optimal value, engine torque reduces.

Note that a lambda value lower than the optimal value (richer mixture) produces lower torque.

The calculation also takes into account the torque used by the engine itself, i.e. the internal friction. Values for air mass, engine speed, coolant temperature and idling torque are used for this calculation.





TCM





Torque limitation, automatic gearbox
Engine torque must occasionally be limited for the sake of comfort in gear changing and in certain cases also for reasons of durability.

Engine torque limitation, bus from TCM
TCM determines the maximum engine torque to be allowed. During gear changing, engine torque is often reduced somewhat for comfort. Torque can also be reduced for reasons of durability.

Engine torque limitation, stalling
Engine torque for a stalling gearbox is limited to 200 Nm to protect the gearbox.





Manual Gearbox





Torque limitation, manual gearbox
ECM calculates the current gear via vehicle speed and engine speed. The following gears are subject to torque limitation:
^ 1st gear
^ Reverse gear