GF07.61-P-3028MIG Intake Manifold Switchover, Function

GF07.61-P-3028MIG Intake Manifold Switchover, Function
- as of model year 09


Function requirements for intake manifold switchover, general points
^ Circuit 87M ON (engine control ON)
^ Engine running

Intake manifold switchover, general points
The intake manifold switchover is used to switch between the long and short intake tracts. In this way the engine torque is optimized.

The ME-SFI control unit (N3/10) actuates the intake manifold switchover according to the signals from the following sensors:
- Hot film MAF sensor (B2/5), engine load
- Crankshaft Hall sensor (B70), motor speed

Intake manifold switchover function sequence
For the intake manifold switchover, the ME-SFI control unit uses a ground signal to actuate the variable intake manifold switchover valve (Y22/6), according to engine load and engine speed.

On engine 272, the switchover flaps for one cylinder bank are connected by a shaft and are each actuated by a vacuum unit. On engine 273, the two shafts are connected by a linkage and are both actuated by one vacuum unit.
The vacuum unit or vacuum units is/are connected to the variable intake manifold switchover valve by hose lines.

When the variable intake manifold switchover valve is not actuated, the vacuum units are ventilated and the switchover flaps are opened by spring force.
Air intake takes place over the short intake tracts.

When the variable intake manifold switchover valve is actuated, the vacuum units are charged with vacuum from the vacuum reservoir. This causes the switchover flaps to close, and air is admitted through the long intake tract.

Short intake tracts (section in cylinder level)

Component Identification:

The variable length intake manifold switchover flaps are opened in the following conditions:
- Engine load > 50 %
- Engine speed >3500 rpm

Air intake takes place over the short intake tracts. In this way an increase in engine torque and output is achieved.

Long intake tracts (section in cylinder level)

Component Identification:

The variable length intake manifold switchover flaps are closed in the following conditions:
- Engine speed <3500 rpm

Air intake takes place over the long intake tracts. In this way an increase in engine torque and output is achieved.