Supercharger Boost Pressure Control Function

Supercharger Boost Pressure Control Function

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




50 Supercharger
50/2 Pressure connection fitting (supercharger output)
76 Recirculated air pipe
B2/5 Hot film mass air flow sensor
K40 Relay module
K40/4 Fuse and relay module
L5 Crankshaft position sensor
M16/1 Electronic accelerator (EA)/Cruise control (CC)/Idle speed control (ISC) actuator
M16/7 Recirculated air flap actuator
N3/4 HFM-SFI control module
N3/10 ME-SFI control module
Y2/1 Electromagnetic clutch

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.