TURBOCOMPONENTS

A turbo consists of many parts manufactured from special materials that have to endure temperatures approaching 1 000 degrees Celsius while the rotating parts may exceed 200 000 r/min. Therefore, all the rotating components are individually balanced by a machine cutting away small amounts of excess material. The nal centre rotating-hub assembly is then balanced to a ne degree on a machine similar in operation to a tyre-balancing unit but which is able to test at maximum speeds employing compressed air. The nal adjustment is done by removing minimal material from the assembly nut on the shaft.

The following main components are important when it comes to reliability.

1 HOUSING

The compressor (and turbine) housing’s shape is de ned by the area and radius dimensions, and forms the outer shell of the turbo.

2 WHEELS

The compressor and turbine wheels consist of radial blades designed to compress the intake air and extract energy from the exhaust gas. The design, size and shape determine the air ow, pressure ratio and ef ciency on the compressor side and power capability (and ef ciency) on the turbine side. These two wheels need to be perfectly matched to each other and the engine application.

3 SHAFT

The shaft connects the compressor wheel to the turbine wheel and runs through the journal (or ball) bearings.

4 BEARINGS

Journal bearings lubricated with engine oil are most common, although high-end turbochargers now employ ball bearings.

5 THRUST BEARING

This bearing plate deals with the axial loads on the shaft of the turbocharger.

6 TURBO “SEAL”

A seal is an improper term to describe the component because it’s actually closer to a piston ring. This metal ring prevents oil leaking to the compressor or turbine side through the sealing action, but also by allowing pressurised air (or exhaust gas) through the ring gap to keep the oil back into the centre housing.