Other Limitations

Other Limitations

Engine protection function
Under certain operating conditions, engine torque must be limited to prevent damage. Examples of protective functions:





^ When driving at high altitudes, engine torque may be limited to prevent the turbocharger from overrevving.
^ When the engine is cold, engine torque is limited to prevent engine damage.
^ If there is a risk of overheating, engine torque is limited by restricting air mass and through fuel cut-off.
^ Limitation of maximum permissible engine speed.

Torque limitation in the event of a diagnostic trouble code
Certain diagnostic trouble codes cause torque to be limited in order to prevent damage.





Brake
Maximum permissible engine torque must be limited when the brake pedal is depressed for reasons of durability.





Safety-related fault in throttle control.
If there is a safety-related fault in the throttle control, throttle control is in limp-home mode or pedal sensor is in limp-home mode, the engine's maximum torque is limited.





Misfiring
To protect the turbocharger and the catalytic converter in the event of misfiring, engine torque is limited if there is a risk of overheating. The degree of misfiring that is allowed without engine torque limitation depends on the current operating point, engine speed and load.





Emission limitation
Increases in engine torque can be limited in order to reduce emissions. A rapid increase in torque requires relatively high fuel enrichment, giving higher exhaust emissions.





Active surge dampening
Surges (variations) may occur during acceleration. These are caused by sudden increases in engine torque combined with a certain elasticity in the power train and engine mountings. Through compensation, these variations can be reduced or eliminated completely.





The anti-surge function detects variations in engine speed and dampens them by changing engine torque via ignition timing, which is usually retarded.

Maximum permissible vehicle speed
If vehicle speed exceeds the programmed value for speed limitation, the function limits engine torque, thus limiting the car's maximum speed.