Audi 4.2-liter V8 FSI, Обучение по обслуживанию

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Engine Mechanical
9
Fine Oil Separator
Blow-by gas volume is dependent on engine load and
RPM. The fine oil (“oil spray”) is separated by means
of a cyclone separator. Cyclone separators have a high
separation efficiency over only a small volumetric range.
For that reason, one, two, or three cyclones of the fine oil
separator operate in parallel, depending on the gas-flow
rate.
The cyclones are released by the control piston. The
displacement of the control piston against its spring
force is dependent on the gas-flow rate. Piston ring
flutter at very high engine RPMs and low engine load can
result in a very high gas-flow rate.
The crankcase internal pressure is set by the two-stage
pressure control valve. The bypass valve, together with
the control piston, ensures that the cyclones operate at
the optimum operating point (if the volumetric flow rate
is too high or too low, it will impair the functioning of the
cyclones).
When the bypass valve opens, a fraction of the blow-by
gas flows to the engine untreated, but the remainder is
optimally treated by the cyclones.
The separated oil is collected in an oil reservoir beneath
the cyclones. The oil cannot drain out of the reservoir
until the oil drain valve is opened. The oil drain valve
is closed as long as the pressure in the crankcase, i.e.,
below the valves, is higher than in the oil separator. The
valve opens automatically due to gravity only at very
low engine RPMs or when the engine is at a standstill,
because the pressure conditions above and below the
valve are in equilibrium.
The crankcase ventilation system also includes the
crankcase breather. Air is extracted downstream of the
air filter and flows through a non-return valve into the
crankcase from above.
The non-return valve is located at the end of the vent
line and is bolted between the two cylinder banks in the
engine block.
A damping chamber is located below the non-return
valve in the engine block. This prevents non-return valve
flutter and eliminates noise.
A restrictor bore connects this chamber to the inner
chamber of the crankcase. It has the task of supplying
only a defined volume of fresh air to the crankcase.
377_011
Control Piston
Oil Reservoir
Triple Cyclones
Oil Drain Valve