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D
E
4
AILY
URO
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Oil vapour recirculation (Blow-by)
Part of the gas produced by the combustion during the
engine operation blows by the piston snap ring ports, in the
oil sump, and mixes with the oil vapours present in the oil
sump. This mixture, conveyed from the chain compartment
to the top, is partially separated from the oil by means of a
device situated on the top side of the distribution cover and
is introduced in the air suction system. This device consists
mainly of a rotating filter (3), fit flush on the stem (1), a high
pressure/shaft control and a cover (2) where the valves (4
and 5), usually closed, are fitted. The diaphragm valve (4)
regulates the partially purified mixture and keeps the pressure
inside the chain compartment around a value of ~ 10 ÷ 15
mbar.
The umbrella valve (5) discharges some of the oil still present
in the mixture coming from the filter (3) in the chain
compartment and the oil condenses in the chamber (6).
Operation
The mixture which passes through the rotating filter (3) is
partially purified from the oil particles, as a result of
centrifugation, and so these particles condense on the cover
walls to return to the lubrication circuit. The resulting purified
mixture is let in through the stem holes (1) and the
diaphragm valve consensus (4) inside the air vent upstream
of the turbocharger. The opening/closing of the valve (4)
depends mainly in the ratio between the pressure operating
the diaphragm (4) and the depression below it. The oil still
present in the mixture coming from the rotating filter (3) and
which condenses in the chamber (6) is drained into the chain
compartment through the umbrella valve (5), when the
pressure that keeps it closed drops as a result of the engine
stop.
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F1C ENGINE
Figure 299
Gas with oil level above 10 g/h
Gas with oil level ~ 0,2 g/h
Condensed oil returning to the oil sump
Base - March 2006
88062
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