Charging, function

W09.00-1016-79

General

Charging on engine 936.912 takes place by a turbocharger (1). Through compression of the suctioned in air in the turbocharger (1) a larger air mass is brought into the combustion chamber.

The following advantages result through this:

 An increase in the engine power and the torque

 Reduction of fuel consumption in comparison to not supercharged diesel engines of the same power output

 Reduction of the pollutant emission

Function

The turbocharger (1) consists of a turbine and a compressor which are fitted to a common shaft (8). The exhaust (E) flows over the turbine wheel (7) and causes this to rotate. This rotational movement is transferred to the compressor impeller (9) over the shaft (8). The compressor impeller (9) compacts the intake air (B) cleaned by the air filter, which heats it in the process. The heated charge air (C) passes over a charge air pipe to the charge air cooler (3). In the charge air cooler (3) the heated charge air (C) is cooled whereby the air density of the fresh gas filling and thus the output of the engine is increased. The cooled charge air (D) subsequently passes from the charge air cooler (3) over the charge air housing (4) into the individual cylinder.

Boost pressure control (via wastegate)

The engine management (MCM) control unit (A4) determines the current boost pressure with the aid of the charge air pressure and temperature sensor (B616). If the boost pressure is too high, it transmits an appropriate message to the boost pressure regulator (Y636) which opens the boost pressure control flap (10) over a linkage. Dependent on how wide the boost pressure control flap (10) is opened there will now be more or less exhaust (E) passed by over a bypass on the turbine wheel (7). Since only part of the exhaust (E) hits the turbine wheel (7) the acceleration is not so strong anymore and the boost pressure drops.