Chevrolet Sonic Repair Manual: Air Intake System Description

Circuit/System Description

The primary function of the air intake system is to provide filtered air to the engine. The system uses a filter element mounted in a housing. The filter housing is remotely mounted and uses intake ducts to route the incoming air into the throttle body. The secondary function of the air intake system is to muffle air induction noise. This is achieved by the use of resonators attached to the air intake ducts. The resonators are tuned to the specific powertrain. The intake air temperature (IAT) sensor is used to measure the temperature of the air entering the engine.

Intake Manifold Tuning Solenoid Valve

The intake manifold tuning solenoid 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 intake manifold tuning solenoid valve is used to change the intake manifold plenum configuration. When the intake manifold tuning solenoid valve is open, the intake manifold is configured to one large plenum. When the intake manifold tuning solenoid 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 intake manifold tuning solenoid valve is closed creating a longer runner path inside the plenum which increases torque. During higher engine speeds and loads, the intake manifold tuning solenoid valve opens creating a shorter runner path inside the plenum which increases horsepower. Ignition voltage is supplied to the intake manifold tuning solenoid valve solenoid through a fuse when the ignition key is turned ON. The intake manifold tuning solenoid 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 intake manifold tuning solenoid valve, energizing the intake manifold tuning solenoid valve and allowing a vacuum from the intake manifold tuning valve vacuum tank to be applied to the intake manifold tuning actuator valve. The intake manifold tuning actuator valve then opens the intake manifold tuning valve in the intake manifold for desired performance. The variable intake manifold system consists of the following components:

• The intake manifold tuning solenoid valve
• The intake manifold tuning valve vacuum reservoir
• The intake manifold tuning vacuum actuator
• The intake manifold tuning valve
• An intake manifold

Ignition voltage is supplied directly to the intake manifold tuning solenoid valve. The engine control module (ECM) controls the intake manifold tuning solenoid valve by grounding the control circuit via an internal driver switch. The primary function of the driver is to supply ground for the intake manifold tuning solenoid valve. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the voltage on the control circuit.

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