A cold air intake (CAI) replaces the restrictive factory air box with a high-flow filter and smooth piping routed away from engine heat. By drawing cooler air from the fender well or front grille, it increases the air density entering the combustion chamber. This modification slightly improves horsepower and creates a much louder, aggressive induction sound under heavy throttle.
I bolted on a CAI and a cat-back exhaust over the weekend, and the throttle response is way sharper.
Most cheap aftermarket CAIs actually sit in the hot engine bay without a heat shield, turning them into hot air intakes that lose power.
Related terms
Intake system
The complete path that channels outside air into the engine combustion chambers.
Intake manifold
The engine component that distributes incoming air or air-fuel mixture evenly to each cylinder.
Forced induction
The process of compressing intake air to increase the power output of an internal combustion engine.