Variable Induction System: Description and Operation
Intake Air System:
The Intake Air system provides clean air to the engine, optimizes airflow and reduces unwanted induction noise. The Intake Air System consists of an air cleaner assembly, resonator assemblies and hoses. The main component of the intake air system is the air cleaner assembly. The air cleaner assembly houses the air cleaner element that removes potential engine contaminants, particularly abrasive types. The Mass Air Flow (MAF) sensor is attached internally or externally to the air cleaner assembly and measures the quantity of air delivered to the engine combustion chamber. The MAF sensor can be serviced or replaced as an individual component. The intake air system also contains a sensor that measures the intake air temperature which may also be integrated with the MAF sensor. (Refer to Electronic EC Hardware - PCM Inputs for additional information on the MAF and IAT sensors.) Air induction resonators can be separate components or part of the intake air housing (i.e., conical air cleaner). The function of a resonator is to reduce induction noise. The air induction components are connected to each other and to the throttle body assembly with hoses.
There are two basic types of intake air sub-systems:
- Intake Manifold Runner Control (IMRC) electric actuated system
- Intake Manifold Tuning (IMT) Valve
These subsystems are used to provide increased intake airflow to improve torque and performance. The overall quantity of air metered to the engine is controlled by the throttle body.
Intake Manifold Runner Control (IMRC) - Electric Actuated:
Intake Manifold Runner Control (IMRC) Electric Actuated System
The Intake Manifold Runner Control Electric Actuated system consists of a remote mounted motorized actuator with an attaching cable for each housing on each bank. Some applications will use one cable for both banks. The cable of linkage attaches to the housing butterfly plate levers. The Escort/Tracer 2.0L (2V) IMRC uses a motorized actuator mounted directly to a single housing without the use of a cable. Each IMRC housing is an aluminum casting with two intake air passages for each cylinder. One passage is always open and the other is opened and closed with a butterfly valve plate. The housing uses a return spring to hold the butterfly valve plates closed. The motorized actuator houses an internal switch or switches, depending on the application, to provide feedback to the PCM indicating cable and butterfly valve plate position.
Below approximately 3000 rpm, the motorized actuator will not be energized. This will allow the cable to fully extend and the butterfly valve plates to remain closed. Above approximately 3000 rpm, the motorized actuator will be energized. The attaching cable will pull the butterfly valve plates into the open position. Some vehicles will activate the IMRC near 1500 rpm.
WARNING: SUBSTANTIAL OPENING AND CLOSING TORQUE IS APPLIED BY THIS SYSTEM. TO PREVENT INJURY, BE CAREFUL TO KEEP FINGERS AWAY FROM LEVER MECHANISMS WHEN ACTUATED.
1. The PCM uses the TP sensor and CKP 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 rpm to open the valve plates.
2. The PCM uses the information from the input signals to control the IMRC motorized actuator based upon rpm and changes in throttle position.
3. The PCM energizes the actuator to pull the butterfly plates open with the cable(s) or linkage.
4. The IMRC housing contain butterfly plates to allow increased air flow.
Intake Manifold Tuning (IMT) Valve
The intake manifold tuning valve is a motorized actuated unit mounted directly to the intake manifold. The IMT valve actuator controls a shutter device attached to the actuator shaft. There is no monitor input to the PCM with this system to indicate shutter position.
The IMT valve motorized unit will not be energized below approximately 2600 rpm. The shutter will be in the closed position not allowing airflow blend to occur in the intake manifold. Above approximately 2600 rpm, the motorized unit will be energized. The motorized unit will be commanded on by the PCM initially at a 100 percent duty cycle to move the shutter to the open position and then falling to approximately 50 percent to continue to hold the shutter open.
1. The PCM uses the TP sensor and CKP signals to determine activation of the IMT valve system. There must be a positive change in voltage from the TP sensor along with the increase in rpm to open the shutter.
2. The PCM uses the information from the input signals to control the IMT valve.
3. When commanded on by the PCM, the motorized actuator shutter opens up the end of the vertical separating wall at high engine speeds to allow both sides of the manifold to blend together.