Charging, function

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General

Charging takes place via an exhaust gas turbocharger (1).

By compressing the suctioned in air in the exhaust gas 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 ATL (1) consists of a turbine and a compressor which are fitted to a joint shaft (6).

The exhaust (D) flows over the turbine wheel (3) and causes this to rotate. This rotational movement is transferred to the compressor wheel (5) via the shaft (6).

Through the compressor impeller (5) the intake air is compacted by the air filter (A) and passes over a charge air pipe to the charge air cooler.

In the charge air cooler the compacted air is cooled whereby the air density of the fresh gas filling and thus the output of the engine is increased.

The charge air then passes from the charge air cooler (C) via the charge-air distributor (2) into the individual cylinders.

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Boost pressure control (over wastegate)

The engine management (MCM) control unit (A4) determines the current boost pressure via the charge air pressure and temperature sensor in the charge air pipe (B608).

If the engine management (MCM) control unit (A4) recognizes that the current boost pressure is too high, it limits the boost pressure in that it actuates the boost pressure regulator (Y636) with an appropriate pulse width modulated signal. Via the duty cycle of this signal, the engine management (MCM) control unit (A4) can influence how much pressure (up to 2.8 bar) is applied to the pressure cell (4). The valve (7) is opened over a linkage according to this pressure, so that more or less exhaust (D) is passed over the bypass opening (8) on the turbine wheel (3) depending on how far it is opened.

Since only part of the exhaust (D) hits the turbine wheel (3) the acceleration is not so strong anymore and the boost pressure drops.

Turbocharger protection function

To protect the exhaust gas turbocharger, the rotor speed of the exhaust gas turbocharger (1) and the temperature of the intake air from the air filter (A) are additionally monitored on the compressor inlet for vehicles with engine version Euro VI Standard.

This occurs with the aid of the turbine wheel rpm sensor (B610) and the temperature sensor downstream of the air filter (B611).

Since these sensors are not available for vehicles with engine version Euro V Standard, the engine management (MCM) control unit (A4) is oriented toward the ambient temperature and the altitude of the vehicle. The latter is determined using the installed atmospheric pressure sensor.

Dependent on the determined values and values stored in the characteristics maps for the turbocharger protection function the engine management (MCM) control unit (A4) adapts the injection which leads to a lowering of the combustion temperature.

One indirect effect of actuation of the boost pressure regulator (Y636) can be reduction of the rotor speed of the ATL.