A cold air intake is an air intake system which takes the intake air charge from outside of the engine compartment. Most factory air intake breathers are placed within the confines of the engine compartment where the intake air charge consists of hot air. By installing a cold air intake on a vehicle and drawing cool air from outside of the engine compartment, a vehicle can pick up horsepower and have a noticeable feel of added power and throttle response. The typical cold air intake is routed under the vehicle near the bottom of the front bumper or inside the front fender near the wheel well.
The cooler the intake air charge is, the more power the engine will make. Cold air intake systems use this fact to generate more power with a minimal amount of work and cost to the vehicle owner. The factory air box and inlet tubing is restrictive and ineffective when it comes to performance. Many of the after-market cold air intakes utilize a portion of the factory intake system and add a section that is re-routed to a better location in the cooler air flow. Others use an entirely recreated system with as few turns and bends as possible. Both types of cold air intakes typically utilize a different free-breathing air filter.
The free-breathing air filter is often worth several units of horsepower in and of itself. The factory air breather and air filter is often a small, flat design which hinders air flow and creates a blockage of the intake air charge. This intake air charge acts much like the ram air systems of the 1960s, where cold air was actually forced into the engine by placing the cold air intake tubing in the front of the vehicle. As the vehicle was driven, the air was scooped up by the forward-facing intake openings and forced into the engine. The ram air system was perhaps the first cold air intake system.
Other early attempts at forcing cold air into an engine were found in the use of hood scoops. A hood scoop has an opening facing forward and allows the air to be forced into the engine as the vehicle is driven. The bulk and vision impairment of the hood scoop forced the development of the internal cold air intake system popular on vehicles all over the world today. In most cases, the factory offers a cold air intake kit for the vehicle owner to add to his vehicle and improve the performance himself.