Turbocharger - Diesel: Operation
The turbine wheel is driven by exhaust gases. As exhaust gas flow increases with engine speed, the turbine speed increases and compressor discharge increases. The turbocharger is designed to provide a relatively high discharge pressure at mid-range RPM.
Turbocharger lubrication is supplied by the engine oiling system. The shaft is supported by bearings using pressurized oil for lubrication. The shaft seals are a piston ring type. Oil supply and pressure must be sufficient to prevent shaft bearing failure.
The wastegate actuator monitors discharge pressure from compressor. When pressure reaches 10 psi (.70 kg/cm2 ), actuator begins to open wastegate. As pressure increases, the regulator gradually increases wastegate opening.
Excessive compressor pressures may damage engine by inducing an overload, and are normally prevented by wastegate actuator. In case of failure of that system, a blow-off valve mounted on the end of the intake manifold is activated.