Quantity control at part load/full load - function

At partial load or full load the delivery quantity is primarily adjusted to meet requests from the driver.

If the specified torque requested by the driver changes in that he, for example, presses on the accelerator pedal, the engine control (MR) alters the fuel delivery quantity (over the delivery angle) in such a way that the delivered actual torque is exactly the same as the specified torque requested by the driver.

Limitation of the specified torque, for example to stay within the legally prescribed maximum speed, because of a control intervention function of the antilock brake system (ABS) or the acceleration slip regulation (ASR) or to protect the engine will lead to limitation of the fuel delivery quantity and therefore a corresponding change in the delivery angle.

-----------------------------------------------------------------------------------------

The delivery angle which is determined over performance maps in the MR/PLN control unit is dependent on the following input parameter:

 Engine speed

 Air mass

 Engine temperature

 Fuel temperature

The last parameter is only determined on engine 541.9 up to engine end no. 094097 and on engine 542.9 up to engine end no. 094246 over a fuel temperature sensor. The fuel temperature for all other engines (engine 541.9 as of engine end no. 094098 and engine 542.9 as of engine end no. 094247) is also determined over a performance map.

-----------------------------------------------------------------------------------------

It is only the altitude correction and smoke limitation in the engine control (MR) which can additionally influence the delivery angle:

Altitude correction

There is an atmospheric pressure sensor inside the MR/PLN control unit. It determines the air pressure of the ambient air from which the engine control (MR) deduces the altitude correction.

The altitude correction prevents too much fuel being injected at a high altitude.

Smoke limit

The quantity of fuel is limited over a smoke limitation map so that no output of smoke occurs.