Controlling diesel air intake is very vital if you have diesel engine vehicle. Since a diesel engine requires close tolerances in order to achieve its compression ratio, and since most diesel engines are supercharged or turbo charged, the air that enters it must be clean and free of debris, and also as cool as possible. To improve the efficiency of a supercharged or turbo charged engine, the compressed air must be cooled once it has been compressed. These tasks are performed by the air intake system of the vehicle.