Internal combustion engines use spark to detonate an air-fuel mixture. The air in this mixture enters the engine through the air intake system, which consists of at least an air filter, housing, and duct hose to bring air in. The system may include sensors and some other parts that help optimize intake.
Cold air intakes (CAI) are popular mods for this system, because they free up intake air flow and tend to be simple to install. Freer flow lets more air into the engine so it can run with more power. CAIs can commonly be installed by replacing the air filter, housing, and duct with the CAI assembly.
Learn more about air intake systems: You can read these informative articles or talk to an associate at the nearest AutoZone.