Charging function

Forced induction is used to provide the engine with the appropriate boost pressure in all operating phases, thus increasing engine power and torque.

In turbocharging, the flow energy of the exhaust gases is used to drive the turbocharger.

The turbocharger draws in fresh air at the compressor inlet, pre-compresses it, then passes it through the compressor outlet, the charge air pipe, the charge air cooler and the air intake manifold to the individual cylinders in the engine.

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Turbocharging is controlled by the boost pressure control, and regulated by the CDI control unit according to the following values and their related components:

 Engine speed, from the crankshaft position sensor

 Injection quantity, determined from the injection time of the fuel injectors and the fuel pressure in the rail (the fuel pressure in the rail is measured by the rail pressure sensor)

 Coolant temperature, from the coolant temperature sensor

 Charge air temperature, from the charge air temperature sensor

 Atmospheric pressure, from the pressure sensor downstream of the air filter

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After evaluating the input signals, the CDI control unit actuates the boost pressure positioner with a pulse width modulation (PWM) signal, according to the boost pressure performance map.

The position of the guide vanes in the turbocharger is adjusted by the control rods of the boost pressure positioner. This directs the exhaust gases that drive the turbocharger, thus controlling its rotational speed.

The turbocharger rotational speed determines the quantity of pre-compressed air, and thus the boost pressure. The boost pressure is monitored continuously by the boost pressure sensor, and the corresponding signal is sent to the CDI control unit.