GF07.10-P-1017MAW Intake Manifold Switchover, Function

GF07.10-P-1017MAW Intake Manifold Switchover, Function
ENGINES 156.9 in MODEL 204.0 /2 /3, 212.0 /2

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

Intake manifold switchover, general points
The intake manifold switchover is used to switch between the long and short intake tracts. This optimizes the engine torque.

The ME-SFI [ME] control unit (N3/10) actuates the intake manifold switchover according to the signals from the following sensors:

- LH and RH hot film MAF sensor (B2/6, B2/7), engine load
- Crankshaft Hall sensor (B70), engine speed

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

The switchover flaps are operated by the variable intake manifold vacuum unit by means of a linkage.
The vacuum unit is connected to the intake manifold switchover valve by a hose line.

When the intake manifold switchover valve is not actuated, the vacuum unit is ventilated and the switchover flaps are opened by spring force. Air intake takes place over the short intake tracts.
When the switchover valve is actuated, the vacuum unit is charged with vacuum from the vacuum reservoir. This causes the switchover flaps to close, and air is admitted through the long intake tract.





Switchover flaps open (Cross-section at cylinder level)

A Throttle valve
B Variable flap
C Intake port for left cylinder head
D Intake port for right cylinder head

At low engine speed and low engine load or at high engine speed, the variable intake manifold switches to the short intake tract. The short intake tract allows the engine to reach high rpm.

Switchover flaps closed (Cross-section at cylinder level)

A Throttle valve
B Variable flap
C Intake port for left cylinder head
D Intake port for right cylinder head

The variable intake manifold ensures a full torque curve at low engine speed and high engine load.