Turbocharging, function

Charging function requirements

 Circuit 61 ON

 No deceleration mode

Supercharging

The compressor makes it possible to raise engine torque, particularly in the lower rpm range.

The intake air is compressed in the compressor. The intake air (charge air) is heated by compression and then cooled in the charge air cooler. Compressing the charge air raises the volumetric efficiency of the cylinder, which increases the engine torque and power output.

For this purpose, the ME-SFI control unit (N3/29) reads the following sensors:

- Hot film MAF sensor (B2/13), engine load

- Charge air temperature sensor (B17/14), charge air temperature

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- Atmospheric pressure sensor (B18/4), atmospheric pressure

- Accelerator pedal module (B37/3), load request by driver

- Crankshaft sensor (L5/12), engine speed

- Actual value potentiometer for air recirculation flap (M16/46r1), recirculation flap position

- Knock sensor (A16/7), knock control

- Coolant temperature sensor (B11/18), coolant temperature

- Boost pressure sensor (B5/7), charge air pressure

The charging is divided into the following subfunctions:

 Boost pressure control

 Air recirculation flap actuator limp-home mode (M16/46)

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Boost pressure control

Boost pressure control takes place performance map dependent by the ME-SFI [ME] control unit with the aid of air recirculation flap actuator.

The air recirculation flap opens or closes the air recirculation line continuously. If the air recirculation flap is opened, the boost pressure drops since the charge air is led again to the compressor rather than to the individual cylinders.

 Charging increases the intake air mass detected by the hot film MAF sensor. The ME-SFI [ME] control unit then lengthens the injection time of the fuel injection valves accordingly.

Recirculated air flap actuator, emergency mode

The actual value potentiometer for the air recirculation flap consists of the actual value potentiometer (sliding contact 1) (M16/46r3) and the actual value potentiometer (sliding contact 2) (M16/46r4). The intact actual value potentiometer is switched over for failure of one of the two actual value potentiometers.

If the actuator motor (M16/46m1) or the actual value potentiometer for the air recirculation flap fails, the air recirculation flap is opened by the integral return spring, whereby no further boost pressure can be built up and the engine power is limited.