Driving operation, function

W07.16-1060-79

If the drive control (CPC) control unit (A3) does not demand any idle or working speed control then this is normal driving mode. In driving mode the injection quantity is primarily adjusted according to requests from the driver. This means that the torque specification of the engine is primarily dependent on the position of the accelerator pedal. It is only in certain situations that it can happen that the engine speed is adapted independently of the accelerator pedal position or of the specified torque request, for example for downshifting for rotational speed comparison between the main shaft and the countershaft.

During vehicle operation, the engine management control unit (MCM) (A4) therefore initially compares the specified engine torque incoming from the drive control control unit (CPC) (A3), which is derived i.e.from the position of the accelerator pedal and provided via the drive CAN (CAN 4), with the current actual engine torque, which represents the engine's actual operating conditions.

If the required engine torque is less than the current actual engine torque, the engine management (MCM) control unit (A4) reduces the injection quantity, and if the required engine torque is greater than the current actual engine torque then it increases the injection quantity.

 The engine management (MCM) control unit (A4) can limit the specified engine torque transmitted by the drive control (CPC) control unit (A3) for engine protection reasons, e.g. if the coolant temperature exceeds a specific value or the engine reaches its final or maximum governed rpm to comply with the maximum permissible speed or due to a control intervention function of the anti-lock braking system (ABS) or the anti-slip control (ASR).

Limitation of the required engine torque always leads to limitation of the injection quantity.

The injection quantity is also dependent on the following input parameters:

 Engine speed

 Air mass

 Coolant temperature

 Fuel temperature

The altitude correction and smoke emission limitation can also influence the injection quantity (actuation period) as well as the start of actuation of the fuel injectors.

Altitude correction

The altitude correction is primarily designed in such a way that the turbine speed, the compressor outlet temperature and the turbine inlet temperature of the ATL, as well as the air/fuel ratio λ (Lambda) does not exceed or drop below established limits. To do this, the exhaust gas recirculation rate (EGR rate), the actuation begin as well as the actuation period (injection quantity) for fuel injectors for cylinder 1 to 6 (Y608 to Y613) are adapted.

Smoke limit

The fuel quantity is limited via the smoke limitation characteristics so that virtually no output of smoke occurs.

If the specified engine torque is negative, e.g. in deceleration mode, and if the motor speed lies above 950 rpm, the engine management (MCM) control unit (A4) interrupts actuation of the fuel injectors for cylinders 1 to 6 ( Y608 to Y613) and lowers the fuel pressure in the rail via the rail quantity control valve (Y642).

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. The driver can select between 3 brake stages.

If the motor speed drops below 950 rpm, the engine management (MCM) control unit (A4) increases the fuel pressure in the rail over the rail quantity control valve (Y642) and actuates the fuel injectors for cylinders 1 to 6 (Y608 to Y613).

The exhaust gas recirculation (EGR) is active throughout the whole driving mode to reduce the nitrous oxide emissions.

In the case of the exhaust gas recirculation (EGR), the suctioned out or supercharged fresh air is mixed with exhaust gas. This leads to the situation where the oxygen content of the suctioned out or supercharged air drops and its specific heat increases.

One can therefore achieve a lower combustion temperature and thus reduced output of nitrogen oxides (NOx), whose proportion increases with increasing combustion temperatures. The amount of exhaust gases produced is also reduced.