Supercharger boost pressure control function - GF09.50-P-3002G

ENGINE 111.944 in MODEL 202.025 

ENGINE 111.975 in MODEL 202.024 

ENGINE 111.973 in MODEL 170.447 

ENGINE 111.943 in MODEL 170.445 

Task 

Regulating boost pressure at part load by means of the recirculated air flap.

Design 

The recirculated air flap actuator is positioned at the top part of the air cleaner for regulating the boost pressure. The recirculated air flap can be steplessly operated between 0° - 90° by means of a pulse width modulated (PWM) signal. As a result of this, the boost pressure downstream of the supercharger is regulated through the recirculated air pipe.

The flap is always closed at full throttle (maximum boost pressure).

Function 

When the supercharger is engaged, a pulse width modulating (PWM) signal is supplied simultaneously to the recirculated air flap by the engine control module.

• On/off ratio about 100%: recirculated air flap closed (b), maximum boost pressure (e.g. full throttle)
• On/off ratio about 10%: recirculated air flap open (a), no boost pressure (aspirated mode through recirculated air pipe)

The boost pressure is determined indirectly from the boost pressure map on the basis of the following parameters:

• engine speed
• air mass
• throttle valve position

If the momentary boost pressure differs from the specified pressure, the recirculated air flap actuator is operated accordingly.

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