The Turbocharger Wastegate

Turbocharger wastegate.

The turbocharger wastegate controls the turbocharger's output. It opens to divert exhaust away from the turbine wheel, depriving it of its source of energy. Without this necessary reduction in output, excessive manifold and cylinder pressures would damage vital engine components. When manifold pressures reach their maximum, the wastegate opens, depriving the turbine wheel of exhaust and allowing the compressor wheel to slow, reducing pressure. Once boost pressure is under control and reaches normal operating pressure, the wastegate closes.

Turbocharger cutaway view.

A turbocharger is an exhaust-driven pump and compressor that increases air intake volume. It improves the volumetric efficiency of an engine. Because a turbocharger is driven by expanding exhaust gases, it is said to be a free source of boost.

Turbocharger Function

Expanding exhaust gases drive the turbine wheel. It's fastened to a shaft that drives the compressor wheel. The compressor wheel compresses the air-fuel charge in the intake manifold. This compressed charge is denser in comparison to a normally aspirated engine. Aspirated engines rely on the downward stroke of the pistons to create low pressure or vacuum in the intake manifold. A turbocharged engine's denser charge is forced into the cylinders by the increased intake manifold pressure.

Turbocharged engines are port injected and have a lower compression ratio than standard engines. The parts are usually not interchangeable.

Turbocharger Bearing Failure

Turbocharger bearing failure.

Premature failure is typically due to a lack of maintenance, contaminated, and unchanged oil result in bearing damage. Turbocharger bearings spin at very high speeds; they quickly overheat if not lubricated sufficiently. One of the symptoms of a faulty turbocharger is blue-gray exhaust from oil leaking past the seals, mixing in with the air-fuel charge, and burning off in the cylinder.

Turbocharger Cooling System

Turbochargers are usually cooled by the engine's cooling system. The cooling system lines to the charger must be maintained and functioning correctly. Check the air tube for obstructions and that the air filter is clean.