Mark VIII V8-4.6L DOHC (1996)
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) energizes the IMRC solenoid that controls the vacuum signal to the vacuum actuator which in turn, opens and
closes the valve plates.
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 to improve 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 electro mechanical vacuum actuator with two valve plates and two air intake passages per
cylinder.
