Positive Crankcase Ventilation: Description and Operation

PURPOSE
To reduce unburned hydro-carbons (HC) emission, crankcase blow-by gas (HC) is routed through the PCV valve to the air intake chamber for combustion in the cylinders.

OPERATION






Blow-by gas is drawn from the crankcase by intake manifold vacuum and crankcase pressure acting on the spring loaded PCV valve, which regulates the size of the opening through the valve.
At idle the passage through the PCV valve is very small, while on acceleration or during heavy load conditions the passage is fully opened.