The target engine torque calculation function is described by way of example on engine 926.9 (6 cylinder).
A3 | Drive control (CPC) control unit |
A6 | Engine management (MR) control unit |
A60 | Exhaust gas aftertreatment (ACM) control unit (only for engines with BlueTEC) |
CAN 4 | Drive train CAN |
CAN 12 | SCR-CAN (only for engines with BlueTEC) |
Z3 | Connector sleeve |
G30.35-A001-80
General
The target engine torque is a value that is calculated by the drive control (CPC) control unit. This value represents the driver's request (e.g. accelerate) under consideration of the current driving condition.
The drive control (CPC) control unit transmits the current target engine torque to the engine management (MR) control unit via drive train CAN.
Function
During operation, the engine management (MR) control unit compares the target engine torque incoming from the drive control (CPC) control unit with the current actual engine torque, which represents the engine's actual operating conditions. The incoming target engine torque is derived, among other things, from the position of the accelerator pedal and provided via drive train CAN.
As well as the accelerator pedal position, the drive control (CPC) control unit evaluates additional information, which can limit the target engine torque depending on the situation:
Exhaust aftertreatment status
Vehicle speed
Further influencing factors depending on the engine area of application
The maximum available engine torque is evaluated in addition to this information. The information about the maximum available engine torque is provided by the engine management (MR) control unit. The engine management (MR) control unit evaluates the current coolant temperature, the fuel temperature and the engine rpm to do this.
The engine management (MR) control unit transfers the maximum engine torque available to the drive control (CPC) control unit. From the sum total of the information, the drive control (CPC) control unit calculates the corresponding target engine torque.
The calculated target engine torque is output as a positive value. For example, if the accelerator pedal is not operated, the target engine torque is specified as "0", and in overrun mode the target engine torque is shown as a negative value.
If the requested target engine torque is less than the current actual engine torque, the engine management (MR) control unit reduces the injection quantity. If the requested target engine torque is greater than the current engine actual torque, it increases the injection quantity.
If the target engine torque is negative, such as in overrun mode, and the engine speed is above 950 rpm, the engine management (MR) control unit interrupts actuation of the single injection pumps for cylinders 1 to 6 (Y600 to Y605). In this way the braking effect of the engine is used and the fuel consumption lowered. The engine brake can be activated to reinforce the braking effect.