System Operation

Turbocharger And Charge Air Cooler (CAC) Systems 

Turbocharger System 

A turbocharger is an exhaust gas driven device used to increase the power output of an engine by the turbocharger compressor increasing the pressure of the air entering the engine. The turbocharger uses exhaust gas energy to drive the turbine connected to the compressor. Compressing the air causes the temperature to increase. The CAC lowers the temperature of compressed air which increases the density of the air before entering the cylinder.

The wastegate on the turbocharger turbine side is opened to reduce exhaust gas flow through the turbine when boost pressure is not needed. A pneumatic actuator controls the wastegate valve opening. The turbocharger wastegate is controlled by the PCM by a PWM signal to the turbocharger wastegate regulating valve solenoid.

The pneumatic wastegate is vacuum actuated, and the poppet style wastegate valve is normally opened at idle or low engine airflow conditions depending on vehicle configuration and requirements such as fuel economy and boost performance. The turbocharger wastegate regulating valve solenoid supplies vacuum to the wastegate actuator to close the poppet style wastegate valve.

The 3 cylinder system uses only 1 turbocharger and 1 turbocharger wastegate.

Charge Air Cooler (CAC) System -- Air To Air Cooled 

The CAC system cools the intake air which has been heated by the turbocharger. The removal of heat from the pressurized air going into the CAC increases the air density which improves combustion efficiency, engine horsepower, and torque. The system consists of a CAC radiator in the grille and tubing to interconnect these components. The CAC is positioned after the turbocharger directly in the flow of the intake air. As the heated air flows through the CAC, it is cooled by the airflow through the grille. The PCM maintains a desirable intake air temperature by monitoring the MAP / IAT2 (located at the intake manifold) sensor.