Variable Induction System: Description and Operation

PURPOSE
Is designed to improve cold engine, low speed, as well as high speed engine performance.

OPERATION
- The Intake Manifold Runner Control (IMRC) system uses two runners and two valve plates per cylinder for air flow into the combustion chamber. The air passages are controlled by valve plates located in between the intake manifold and each of the intake ports in the cylinder heads.

- The Powertrain Control Module (PCM) maintains the valve plate position by using a direct mounted vacuum actuator system. The PCM commands a vacuum control solenoid allowing vacuum to pass to the vacuum actuator drawing the valve plates closed or releasing the vacuum allowing the actuator to push the valve plates open.

- At engine speeds below 3000 rpm, one valve plate is open and the other closed to improve low speed and cold engine performance. At speeds above 3000 rpm, the PCM commands the second valve plate open to allow more air flow, thereby improving high speed engine performance. The PCM also receives a signal from the IMRC system indicating valve plate position.

CONSTRUCTION
Consists of an aluminum housing casting, an IMRC vacuum actuator with two valve plates and two air intake passages per cylinder.