System Description

Turbocharger System Operation:

The turbocharger system provides pressurized air to the intake air system to increase engine power output. The turbocharger utilizes engine exhaust gas to drive a small high-speed turbine and air compressor assembly. In operation, the compressor receives air from the air cleaner and pumps it through an intercooler to the intake plenum.

As increased power is required and the throttle is opened, more air-fuel mixture flows into the combustion chambers. As this increased flow is burned a larger volume of higher energy exhaust gas enters the turbocharger turbine housing. Some of this energy is used to increase the speed if the turbine wheel. The turbine wheel is connected by a shaft to the compressor wheel. The increased speed of the compressor wheel compresses the air it receives and delivers it to the throttle body unit and the intake manifold. The resulting higher pressure in the intake manifold allows a denser charge to enter the combustion chambers. the denser charge develops more power during the combustion cycle.

The intake manifold pressure (boost) is controlled to a correct maximum value by an exhaust bypass valve (wastegate). The valve allows a portion of the exhaust gas to bypass the turbine wheel, thus controlling turbine speed. The wastegate is operated by a spring loaded diaphragm (actuator assembly) that responds to the wastegate solenoid to adjust the boost level.

A compressor bypass valve (air bypass valve) responds to high vacuum during deceleration, and opens to relieve the system of excess high pressure air and accompanying noise. Under conditions of heavy load or acceleration, the boost pressure is controlled by an exhaust bypass device or wastegate.

A solenoid valve, governed by the Electronic Control Assembly (ECA), controls the turbocharger boost pressure applied to the wastegate actuator. If a fault develops in the wastegate, actuator, or solenoid valve, resulting in excessive boost pressures, an overboost warning chime will sound. The chime is activated by the vane airflow meter through the ECA. The knock sensor and knock control unit combine to retard the engine spark advance when engine knocking occurs due to overboost by the turbocharger system.