What is the purpose of the air filter? The primary function of an air filter is to deliver both airflow and superior dirt protection . Air filters is to provide minimum restriction allowing airflow into an engine. In the vast majority of cases increased airflow will increase engine performance measured by horsepower and throttle response (torque). K & N Performance High Flow Air Filter More air entering the engine increases the efficiency of the combustion process creating more horsepower and torque. Horsepower is a measure of the engine's maximum power while torque measures how quickly you can accelerate. The K&N High Flow Air Filter is unique in all the world. It uses premium quality oiled cotton gauze sandwiched between layers of wire screen. This special design permits very high flow rates, minimum restriction, maximum filtration, and very long filter life. When dirty, simply wash, re-oil and install. to increase engine performance in both horsepower and thr