Oil Bath Air Filter:

Further to cleaning the air, the intake system is commonly designed to intake fresh air from as far away from the engine as practicable, commonly just outside of the engine's building or enclosure. That gives the engine along with a supply of air which has not been heated through the engine's own waste heat.

Figure: Oil Bath Air Filter

The purpose for ensuring in which an engine's air supply is as cool as probable is that cool air is denser than hot air. This means in which, per unit volume, cool air has more oxygen than hot air. Therefore, cool air gives more oxygen per cylinder charge than less dense, hot air. Further oxygen means a more efficient fuel burn and additional power.

After being filtered, the air is routed through the intake system within the engine's air box or intake manifold. The manifold or air box is the elements in which directs the fresh air to every of the engine's intake valves or ports. The fresh air will be compressed with a blower and possibly cooled before entering the intake manifold or air box if the engine is turbocharged or supercharged. The intake system also serves to decrease the air flow noise.