The concentration of hydrocarbons in the engine crankcase and fuel tank can be many times higher than that recorded in the exhaust gas. The crankcase ventilation system directs crankcase gases to the intake manifold, the oil separation system allows some of the oil to be returned to the oil pan (pic. 4.23).
The crankcase gases enter the combustion chamber for afterburning.
Fuel tank ventilation system (pic. 4.24) directs the fuel tank vapors to the adsorber, which is purged with atmospheric air and gasoline vapors enter the intake manifold for afterburning.