Crankcase ventilation system
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A crankcase ventilation system removes unwanted gases from the crankcase of an internal combustion engine. The system usually consists of a tube, a one-way valve and a vacuum source.
PCV valve on Ford Taunus V4 engine (feeding from left side valve cover into the inlet manifold)
PCV system of a 1995 Mazda MX5 Miata
A PCV valve from a 1995 Mazda MX5 Miata
Piston ring
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A piston ring is a metallic split ring that is attached to the outside of a piston in an internal combustion engine or steam engine.
Crankcase ventilation system
…and a vacuum source (such as the inlet manifold). The unwanted gases, called blow-by, are gases from the combustion chamber which have leaked past the piston rings. Early engines released these gases to the atmosphere simply by leaking them through the crankcase seals. The first specific crankcase ventilation…
Two piston rings mounted on a two-stroke engine piston. The ring gap for the bottom ring is visible in the centre of the image.
Spring-loaded piston rings