Torque request: General

Several different functions, whether they be external or internal control module functions, can request engine torque. This request can be either positive or negative (limitation). ECM combines these sometimes opposing requirements.

The following functions can request positive engine torque. The highest value is selected and sent on to "limitations."

• Pedal request (from driver)
• Cruise control
• TCS/ESP
• Idle speed control
• Compensation for A/C, generator
• Active surge dampening

But it is not always that the requested engine torque can be attained. This can be due to the maximum permissible engine torque for the engine speed in question has already been attained or that TCS/ESP has requested a reduction in torque. The following functions can limit engine torque:

Fig 1: Identifying Torque Request - Communication Diagram (2 Of 2)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

• Maximum permissible engine torque
• TCM
• Manual gearbox
• Engine protection function
• Brake
• Safety-critical fault in throttle control.
• Misfiring
• Emission limitation
• Active surge dampening
• Maximum permissible vehicle speed

Once the engine has been started, all torque requests are combined into a joint driving torque request. When starting the engine, there is a starting torque request that is selected by upon start of the engine. The result - a starting or driving torque request - is sent on to be converted to an air mass request.