Fiat 1995 Brava, Service Manual

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Bravo-Brava ft*» E n g i n e
Fuel system
10.
S Y S T E M FOR R E C I R C U L A T I N G G A S E S C O M I N G F R O M T H E C R A N K C A S E ( B L O W - B Y )
This system controls the emissions from the crankcase of breather gases, made up of mixtures of air, fuel
vapours and burnt gases which escape through the piston seals and of lubricant oil vapours, drawing
them in again and burning them in the engine.
The breather gases coming from the crankcase reach the cylinder head and are directed into two differ-
ent inlets (1) and (2).
With the butterfly open, the gases flow through the inlets (1) and (2) to be drawn into the manifold.
With the butterfly closed the vacuum in the inlet manifold draws in the gases through the intake (1) in
which there is a PCV limiting valve (3) (Positive Crank Ventilation) which shutters the intake.
The PCV valve, in effect, can be modulated and the quantity of gases which pass through is proportional
to the vacuum in the inlet manifold.
When the butterfly valve is completely open (condition A ) , the vacuum inside the inlet manifold is mini-
mal, the spring (5) is completely extended and the PCV valve allows the maximum flow of breather gas-
es.
Viceversa, with the butterfly completely closed (condition B ) , the vacuum inside the manifold is maxi-
mum, this causes the movement of the piston (4) which shutters the opening for the flow of breather
gases inside the PCV valve and thereby restricts the intake into the manifold of the actual gases.
P4A45BJ01
1. Inlet on butterfly casing with PCV
2. Inlet on sleeve
3. PCV valve
4. Piston
5. Spring
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