Intake Manifold Runner Control (IMRC) Vacuum Actuated System
The IMRC subsystem is used to provide increased intake airflow to improve torque, emissions and performance. The IMRC vacuum actuated system consists of a manifold mounted vacuum actuator and a PCM controlled electric solenoid. The linkage from the actuator attaches to the manifold butterfly plate lever. The IMRC actuator and manifold are composite/plastic with a single intake air passage for each cylinder. The passage has a butterfly valve plate that blocks 60% of the opening when actuated, leaving the top of the passage open to generate turbulence. The housing uses a return spring to hold the butterfly valve plates open. The vacuum actuator houses an internal monitor circuit to provide feedback to the PCM indicating the butterfly valve plate position.
On the initial engine start up the IMRC butterfly valve plates may remain open until the desired engine load and speed is reached. Once the desired engine load and speed are met, the IMRC vacuum actuator is energized which allows the manifold vacuum to close the IMRC butterfly valve plates. The IMRC butterfly valve plates open when the engine shuts off during a normal operation and close when the engine restarts.
- The PCM monitors the throttle position (TP) sensor, cylinder head temperature (CHT) sensor, and crankshaft position (CKP) sensor signals to determine activation of the IMRC system. There must be a positive change in voltage from the TP sensor along with the increase in engine load and engine RPM at the proper engine temperature to open the valve plates.
- The PCM uses the information from the input signals to control the IMRC electric solenoid based upon changes in the throttle position, the engine temperature, the engine load, and the RPM.
- The PCM energizes the solenoid with the key on engine running. Vacuum is then applied to the actuator to pull the butterfly plates closed.