Repair Manual MAN-00190
THAR CRDe BS-IV MAY 2012/Rev 1
The repair methods given by the manufacturer in this document are based on the technical specifications at the time of release. The methods may be modified as a result of changes introduced by the
manufacturer in the production of the various component units and accessories from which the vehicles are manufactured. The reproduction, translation, transmission, in part or whole of the present
document, are prohibited without the prior written consent of Mahindra & Mahindra Ltd. The use of this document by any person other than the trained personnel, at the Authorized Service Centre of
Mahindra & Mahindra Ltd., will amount to unauthorized use and shall be liable for penalty/prosecution© 2012 Mahindra & Mahindra Ltd.
Working Principle, Inspection & Fitment procedures of the Turbocharger –
The Turbocharger is basically an axial inflow air compressor, which is driven by an exhaust gas driven
turbine.
The exhausts gases coming out of exhaust manifold impinge on the turbine blade give the drive to
turbine shaft. At the other end of the turbine shaft the compressor is assembled. The whole assembly
is supported on a floating bush. The bush gets an oil supply directly from the engine and has oil film
between the shaft and bearing as well as the bush and the central housing.
The exhaust gases from the Turbine impinge on the turbine blade & rotate the shaft. The compressor
blades at the other end suck the air from the air filter. After compression the temperature of the
compressed air increases thus reducing the air density. Hence if the air is cooled and then the air
density increases thus helping in getting more power as well as improve emissions. The compressed
air is sent to the intercooler, which is mounted just below the radiator. Hence the incoming ram air
also cools the compressed air and gives it to the intake manifold.
The turbocharger is matched to give an optimum boost for the desired engine speed band. A waste
gate controls the boost. The waste gate is used to bypass the excess exhaust gas away from the
turbine and thus maintain the boost as well as control the backpressure. A spring-loaded diaphragm
controls the waste gate.
A flap valve is installed in the turbine housing just before the turbine blade. Opening the valve allows
the excess gases to bypass the turbine. The flap movement is controlled by a push rod, which is
controlled by a spring-loaded diaphragm. At the other end of the diaphragm the compressed air is
sensed through a hose which is connected at a tapping in the compressor housing.
The length of the pushrod, functioning of the diaphragm and the hose connection are essential for the
precise operation of the push rod. Any air leak from the hose connecting the compressor housing to
the waste gate-controlling diaphragm will also affect the performance of the turbocharger/ engine.
Inspection
Inspect the suction side (i.e. up to the air cleaner) for oil traces.
In a close crank case ventilation system it is normal to have oil in this area. These oil particles are
carried from blow bye of the engine, which gets condensed from gas to oil. Look for any undue
gumming of oil, hard carbon particles in this area. If such an observation is present then all the
causes for excess blow symptoms have to be checked and eliminated.
Inspect the compressor and turbine blades for any damage caused by foreign object. The
inspection can be done through the compressor housing inlet and turbine housings outlet.
Inspect the blades outer edge and observe if any rubbing marks are noticed on the housing.
Rotate the shaft wheel assembly by hand and check for freeness, and any binding.
Push the shaft to side and rotate to check for wheel rub. It should turn smoothly.
Lift both end of shaft up and down at the same time and feel for excessive journal bearing
clearance. If clearance is normal then very little shaft movement will be detected.
If all the above checks are satisfactory then the turbocharger can be reused.
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