In modern automobiles, the air must be cleaned before it gets sucked into the engine's air intake plenum and combustion chambers. If not, you run the risk of dust, dirt and debris quickly fouling up the engine, causing poor performance and potentially shortening the life of the car.
Foreign particles act as abrasives on the metal parts of an engine, wearing away at engine bearings, piston rings and cylinders.
Cold Air Intakes
The colder that air is, the more dense it is, and denser air provides more oxygen in any given volume (inside your engine cylinder), allowing your engine to burn more fuel and generate more power.
Commonly, decreasing Air Intake temperature by 10° F will Increase Horsepower and Increase Torque by 1%. A Cool Air Induction System does just that, pulls much cooler air into the engine than your stock Air Intake Box, resulting in an average gain of 5hp-11hp.