Exhaust blow-by gasses are routed from the crankcase to the intake manifold, where they are combined with the fuel/air mixture and burned during combustion. This reduces the amount of hydrocarbons emitted by the exhaust.
A PCV valve is used in the line to prevent the gases in the crankcase from being ignited in case of a backfire. The amount of blow-by gasses entering the mixture is also regulated by the PCV valve, which is spring loaded and has a variable orifice.
The important components of the PCV system are the following:
| Fig. 1: The PCV valve functions differently according
to the engine operating conditions
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| Fig. 2: PCV system flow
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