CCV system

Introducing Blow-by and the PCV System

Internal combustion engines are essentially controlled bombs; air and fuel combust to drive pistons and crankshafts. One byproduct of this violence is power, but there are darker horses to contend with. During combustion, high pressure on the top side of the piston pushes combustion gasses, as well as droplets of oil and fuel, past the piston rings and into the crankcase. This mixture is known as "blow-by."

To keep the crankcase from becoming pressurized, causing issues with oil sealing and robbing the engine of power, blow-by is pulled from the crankcase via the positive crankcase ventilation (PCV) system and routed back into the intake. You may be seeing the problem already; oil and fuel are not what you want in your air intake system. Many modern cars employ some sort of air-oil separator system to minimize the amount of oil and fuel vapors that reach the intake. Due