Variable Induction System: Description and Operation

GF09.20-P-6002MAR Component Description For The Variable Intake Manifold
- ENGINES 156.981 in MODEL 230.470 as of Model Year 09 /Modification Year 08 model refinement package





View of engine from front left
22 Variable intake manifold

Location
The variable intake manifold is located in the middle between cylinder heads.

Task
The variable intake manifold optimizes the engine torque characteristic by switching between different lengths of intake tract.





Design
External structure shown
16 Connector for throttle valve positioner
22a Housing top section for variable intake manifold
22b Housing bottom section for variable intake manifold
22/6 Vacuum unit for variable intake manifold
22/6a Variable intake manifold gearshift linkage
B17 Intake air temperature sensor
B28 Pressure sensor (intake manifold air pressure)
M16/3 Front throttle valve actuator
M16/4 Rear throttle valve actuator
Y22/6 Variable intake manifold switchover valve





Internal structure shown
22/5 Throttle valves
22/7 Variable flaps
22/8 Air guide duct

The variable intake manifold consists of a number of magnesium pressure castings.
When assembled, these form the individual intake pipes and the air collector. The different parts are separated from each other by plastic seals.

The variable intake manifold must not be disassembled down to the housing bottom section and the throttle valve actuator.

Function
The variable intake manifold allows switching between long and short intake tracts. The vibration response of the intake air for different operating conditions is used in a specific way to achieve internal charging.

The variable intake pipe lengths also allows better distribution of the mixture which leads to better combustion and thus to a higher engine torque.

The switchover flaps for one cylinder bank are linked together by a shaft. The two shafts (right and left) are joined by a linkage at the rear of the variable intake manifold, and actuated by the variable intake manifold vacuum unit.
The variable intake manifold vacuum unit is connected via a hose line to the variable intake manifold switchover valve.

If the variable intake manifold switchover valve is actuated by the ME-SFI [ME] control unit (N3/10), it switches the vacuum from the vacuum reservoir through to the variable intake manifold vacuum unit. The variable intake manifold vacuum unit actuates the two shafts and the switchover flaps close off the short intake tracts.

When not actuated, the variable intake manifold vacuum unit admits air and the switchover flaps are opened by a spring in the vacuum unit. This short intake tracts are then open.