Warm air intake

A warm air intake, or WAI, is a system to decrease the amount of air going into a car for the purpose of increasing the fuel efficiency of the internal-combustion engine.

All warm air intakes operate on the principle of decreasing the air density and therefore the amount of oxygen available for combustion with fuel. Warm air from inside the engine bay is used opposed to air taken from the stock intake which may pull in colder (and more dense) air.

It is similar to a cold air intake (CAI), which significantly differs by collecting air from a colder source outside of the engine bay where the air has a higher density and therefore more oxygen.