A turbocharger is an exhaust driven pump and compressor that increases air intake volume. This improves the volumetric efficiency of an engine. Because a turbocharger is driven by expanding exhaust gases unlike a supercharger that is driven by engine power, it is said to be a free source of power boost.
A turbine wheel driven by the expanding exhaust gases is fastened to a common 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 conventional engine that relies on the downward stroke of the pistons to create low pressure or vacuum in the intake manifold. The denser charge is forced into the cylinders by the increased intake manifold pressure to provide additional engine horsepower.
A turbocharger’s output is controlled by the wastegate diaphragm or bypass valve that opens and closes the wastegate. The wastegate opens to divert some of the exhaust away from the turbine, depriving it of its source of energy. Without this necessary reduction in output, manifold and cylinder pressures would damage vital engine components. When manifold pressures reach their maximum, the wastegate opens depriving the turbine of exhaust and allowing the compressor wheel to slow. This reduces boost pressure. Once boost pressures are under control and reach desired operating pressures the wastegate will close.
Most turbocharger failures are oil related. Contaminated and unchanged oil will result in bearing damage. The bearings spin at very high speeds and will overheat or become damaged very quickly. One of the symptoms of a bad turbocharger is blue gray exhaust. This is because as the turbo fails, oil is mixing with the air fuel charge and burning off in the cylinder. Turbochargers are usually cooled by the engine’s cooling system. Inspect the engine’s cooling system and make sure it’s maintained and functioning properly.