Variable Induction System: Description and Operation

PURPOSE
The air induction system improves engine performance by using the Intake Manifold Runner Control (IMRC) assemblies.

CONSTRUCTION
The intake manifold has two runners per cylinder, feeding each of the intake ports in the cylinder heads.
The IMRC is integral to the lower intake manifold.
The assemblies are located between the upper intake and the cylinder head.

OPERATION
The IMRC assemblies provide two air passages for each cylinder.
One air passage is always available to direct throttle input
The other passage switches from closed to open by means of a valve plate, the intake manifold runner control actuator and cables.
- Below 2800 rpm, this valve plate is closed to improve low speed and cold engine performance.
- Above 3500 rpm, this valve plate opens to improve high speed engine performance.

The valve plates are opened and closed by the electric actuator and cable assembly, which is controlled by the PCM.