Turbocharger - Diesel: Operation

The turbine wheel is driven by exhaust gases. A shaft connects the turbine wheel with the compressor wheel. As exhaust gas flow increases with engine speed, the turbine speed increases and consequently compressor discharge increases.

Turbo compressor wheels rotate at a very high speed, requiring the shaft assembly to be carefully balanced. The shaft is supported by bearings using pressurized oil for lubrication. The shaft seals are a piston ring type.

The turbocharger is connected to the standard engine oiling system. Oil supply and pressure must be sufficient to prevent shaft bearing failure. The turbo compressor is designed to provide a relatively high discharge pressure at middle range RPM. To prevent excessive pressure at high speeds, several controlling and regulating devices are required.

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. Blow-off valve will open when pressure reaches 11.4-12.1 psi (.80-.85 kg/cm² ).