Turbocharger (6.5L & 6.6L Diesel)

CAUTION: On a turbocharged engine, any modification to the air intake or exhaust system which upsets the airflow balance may result in serious damage to the engine.

CAUTION: The rotating assembly in the turbocharger can reach speeds of 150,000 RPM. An adequate supply of clean engine oil is essential for cooling and lubrication. Whenever a basic engine bearing has been damaged or the turbocharger is replaced, the oil and oil filter should be changed and the turbocharger flushed with clean engine oil. Loss of pressure or contamination of the oil supply to the turbocharger bearings can result in major turbocharger damage.

The turbocharger is basically an air compressor or air pump. Its major parts include a turbine wheel, shaft, compressor wheel, turbine housing, compressor housing and center housing. The center housing contains a turbine seal, compressor seal and bearings.

The internal combustion engine is an air pump. The amount of power produced by the engine is determined not by the amount of fuel it uses, but by the amount of air it pumps in a certain period of time. Air must mix with fuel to complete the combustion cycle. When the air/fuel ratio reaches a certain point, additional fuel produces only black smoke, not more power; the denser the smoke, the more the engine is being over-fueled.

The turbocharger increases the quantity and density of air in the engine combustion chambers. The increased volume of air allows more fuel to be used while maintaining the proper air/fuel ratio. The increased air and fuel allows the engine to produce more horsepower than a non-turbocharged engine.

The turbocharger uses the normally wasted energy in the engine exhaust gas. As load on the engine is increased and the throttle is opened wider, more air/fuel mixture flows into the combustion chambers. The increased flow is burned and produces a larger volume of exhaust gas. The gas enters the exhaust manifolds, flows through the turbocharger turbine housing and turns the turbine wheel and shaft. The shaft is coupled to the compressor wheel. The compressor wheel compresses the air it receives and sends it to the intake manifold. The higher pressure in the intake manifold allows a denser charge to enter the combustion chambers.

Intake manifold pressure, or "boost", is controlled by an exhaust by-pass valve (6.6L engine), or wastegate (6.5L engine). The wastegate is operated by a spring-loaded, diaphragm-type actuator which responds to boost pressure. The actuator, which is controlled by the wastegate solenoid, opens the wastegate to allow exhaust gases to by-pass the turbine wheel, thereby maintaining the correct boost level. The wastegate solenoid is controlled by the PCM through a turbo boost relay.