For 1990-2009 cars

### Air Induction System

The air induction system provides air with oxygen for the combustion process. The air cleaner keeps dirt from entering the engine. Outside air is drawn into the air cleaner lower assembly and passes through the air cleaner element. Next the air enters the air cleaner upper assembly and flows through the inlet air duct to the throttle body, and into the intake manifold. Finally the air travels into the cylinder head and through the intake port, ending in the combustion chamber. The intake manifold contains the intake air temperature (IAT) sensor.

### Intake Manifold Tuning (IMT) Valve System

The intake manifold tuning (IMT) valve system uses variable air induction tuning in order to achieve maximum performance and efficiency over the entire operating range of the engine. The characteristic torque curve of a normally aspirated engine depends mainly on how the engines average pressure changes over the engine speed range. The average pressure is proportional to the volume of the air mass present in the cylinder when the inlet valve is closed. The design of the inlet system determines how large an air mass can be drawn into a cylinder at a given engine speed. An IMT valve is used to change the intake manifold plenum configuration. When the IMT valve is open, the intake manifold is configured to one large plenum. When the IMT valve is closed, the intake manifold is configured to two smaller plenums. The two intake manifold plenum sizes result in different torque curves which improves performance at low and high engine speeds.

During low speed, high load conditions the IMT valve is closed creating a longer runner path inside the plenum which increases torque. During higher engine speeds and loads, the IMT valve opens creating a shorter runner path inside the plenum which increases horsepower. Ignition 1 voltage is supplied to the IMT valve solenoid through a fuse when the ignition key is turned ON. The IMT valve solenoid is normally closed which will not allow vacuum to pass through it. When the engine speed and load are increased above a calibrated threshold, the ECM provides a ground to the IMT valve solenoid, energizing the IMT valve solenoid and allowing a vacuum from the IMT valve vacuum tank to be applied to the IMT valve actuator valve. The IMT valve actuator valve then opens the IMT valve in the intake manifold for desired performance. The variable intake manifold system consists of the following components:

• | The IMT valve solenoid

• | The IMT valve vacuum reservoir

• | The IMT valve vacuum actuator

• | The IMT valve

• | An intake manifold