The turbocharger is essentially an exhaust
driven blower (Fig. 1). Its purpose is to increase engine
power by supplying compressed air to the combustion
chambers permitting greater fuel consumption at an
efficient air-fuel ratio.
The turbocharger consists basically of the
turbine wheel and shaft assembly, turbine wheel
housing, compressor wheel and housing and the center
Fig. 1. Turbocharger
1. Center Housing
2. Turbine Housing
3. Compressor Housing
The turbine wheel housing, bolted to the center
housing, receives exhaust gases from the engine. The
exhaust gases spin the turbine wheel and shaft in the
range of 70, 000 rpm at rated engine speed and load.
This motion is transferred to the compressor wheel
secured to the other end of the shaft.
Outside air, after passing through the air cleaner,
is piped to the compressor wheel housing which is
clamped to the center housing. Here the air is
compressed and directed into the intake manifold.
The center housing supports the shaft on two
bearings. These bearings "float" on a film of oil and
touch neither the housing or Shaft. Oil to cool and
lubricate the bearings is supplied under pressure through
passages in the center housing. A sealing ring at each
end of the shaft prevents oil from leaking into the turbine
wheel or compressor wheel housings and also prevents
exhaust gases or compressed air from leaking into the
center housing. A thrust collar and thrust washer absorb
any slight axial movement of the shaft.
In a naturally aspirated or normal breathing
engine, air enters the engine at atmospheric pressure,
mixes with a specified amount of fuel and is burned in
the combustion chamber, producing a certain amount of
It was found that if more air could be put into the
combustion chamber (Fig. 2), more fuel could be burned
and greater power produced from the same size engine.
This increased amount of air or air-fuel mixture forced
into the combustion chamber became known as a
Fig. 2. Air Being Forced Into Engine
2. Increased Power
Printed in United States of America