Crankcase Ventilation

It is quite possible that the product of combustion containing nitrogen, water and carbon dioxide may leak through piston rings into the crankcase. The crankcase ventilation is used in all automotive engines. It consists of passing through the crankcase a constant stream of air which picks up and carries away most of the fuel  vapor and water  vapor before they can condense out and dilute the lubricating oil. Air is drawn into the crankcase through the breather cap and is discharged through an outlet tube at the side of the engine. There are two type of crankcase ventilation used in automobile engines.

• Open Crankcase Ventilation. In open crankcase ventilation, the crankcase  vapors are exhausted into atmosphere.

Open Crankcase Ventilation

• Positive Crankcase Ventilation.  In  positive crankcase ventilation, the crankcase  vapors are returned to the engine through the intake manifold, instead of being exhausted into atmosphere. The crankcase out let tube is connected to the intake manifold just beneath the  carburetor, so that the  vapor are drawn into the intake manifold and utilized into the cylinder during the combustion.

Positive Crankcase Ventilation