Engine
SHOP MANUAL MT26-31 - 06.2005
Tier-3 710655-
Ch 1 page 67
Turbocharger
The purpose of the turbocharger is to increase the
volume of air entering the engine’s cylinders. With
more air the engine can burn more fuel and so de-
velop more power and achieve cleaner combustion
than a corresponding engine without supercharg-
ing.
The turbocharger is driven by the engine’s exhaust
gases and consists of a turbine part and a com-
pressor part. The compressor part compresses the
engine’s intake air.
The compressor wheel is mounted on the same
shaft as the turbine wheel. This shaft runs in a bear-
ing housing between the compressor and turbine.
Higher power output from the engine gives more
exhaust fumes and the increased exhaust means
that the turbine wheel and therefore the compres-
sor wheel rotate faster. In this way, the quantity of
air is adapted to engine requirements without any
special control devices.
The turbocharger wheel rotates extremely fast.
At full power, speed is about 100,000 rpm. At the
same time, the temperature on the exhaust side
of the turbine wheel is above 600°C.
This makes big demands on the rotating parts in
regard to balance, cooling and lubrication.
The shaft is mounted in two bushings which rotate
freely in the bearing housing. The bearing hous-
ing seals for the turbine and compressor consist of
seals which are similar to piston rings.
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