MG MG6 Series 2011 Service Manual page 71

Engine Mechanical-1.8T
The oil pump is directly driven from the crankshaft which
incorporates a pressure relief valve. If oil pressure is too high,
the oil pressure relief valve opens and the excess oil is diverted
back to the intake side of the oil pump. Oil leaving via the outlet
port of the oil pump is fed through a full-flow cartridge type
oil filter mounted on an adapter attached to the oil filter head.
The filter incorporates a bypass valve which relieves excess
pressure in the event of a blockage in the filter.
An oil pressure sensor is also fitted into the head outlet port to
monitor the oil pressure at the outflow side of the filter. If the
oil pressure falls below the specified pressure, 0.2 - 0.58 bar,
the sensor switches to earth and illuminates the oil pressure
light.igh pressure oil is then fed into the cylinder block via the
oil rail attached below the main bearing ladder. High pressure
oil is fed through the main oil gallery and then through cross
drillings to direct oil to the main bearings. The crankshaft has
cross-drillings which carry oil from the main bearings to the
big-end bearings.
A passage in the oil pump housing connects to a drilling in the
cylinder block which supplies high pressure oil to an oilway in
the cylinder head, through the cylinder head to two full length
oilways in the camshaft carrier to supply oil to each hydraulic
tappet and camshaft bearings.
The cylinder walls are splash lubricated from the crankshaft.
The con rod small ends are lubricated from oil collected on
the underside of the piston crown. Oil is fed from the con rod
small ends to the gudgeon pins and bushes via a drilling.
A revised engine block and bearing ladder is used.
incorporates a turbocharger oil drain facility. The oil feed
for the turbocharger is taken from the oil filter housing. The
oil circulates around the turbocharger, providing cooling and
lubrication to the bearings. A drain pipe takes the oil from the
turbocharger to a boss on the bearing ladder in the engine.
Turbocharger
The turbocharger is an exhaust gas driven device that supplies
compressed air, or boost, to the engine's cylinders increasing
its volumetric efficiency. The turbine wheel housed in the
Version 2.0
turbine housing receives the hot exhaust gases from the
exhaust manifold, driving the turbine wheel.
is transmitted through a shaft supported by a bearing to
the compressor wheel in the compressor housing.
compressor draws air from the air cleaner and forces the
compressed air, through the intercooler and into the inlet
manifold. This increase in delivered air, when mixed with fuel
at a given air to fuel ratio, gives the effect of increasing the size
of the engine and improving engine performance.
The shaft bearing is supplied with a high pressure oil feed from
the filer housing and returns to the oil rail via a drain tube.
The exhaust gases exit the turbocharger into the exhaust front
pipe.
Boost pressure is limited by the wastegate. The wastegate,
located within the turbocharger, provides a bypass of the
exhaust driven turbine, in order to limit the pressure entering
the engine as the turbocharger's output exceeds the engine's
volumetric flow. A pneumatic actuator controls the wastegate,
bypassing the excess boost pressure in response to a signal
from the boost control solenoid valve.
Crankcase Ventilation
During engine operation a small amount of combustion gases
escape past the piston rings into the crankcase, these are
known as blowby gases.
unburned hydrocarbons (HC), contaminate engine oil and, at
higher engine speeds create excess crankcase pressure that
can lead to oil leakage from seals and gaskets. A positive
crankcase ventilation system is used to vent these gases from
This
the crankcase to the air intake system.
In addition, a one way valve is fitted in the breather hose
between the camshaft cover and the inlet manifold. This valve
is open when the engine is at idle and on overrun, when the
throttle butterfly is closed, and allows crankcase gases to enter
the inlet manifold. The valve closes when the engine is on
boost, preventing crankcase gases from being forced back into
the engine. The gases are diverted, via a separate breather
hose, back into the inlet side of the turbocharger.
Engine
This drive
These gases, formed mainly of
The
55