Have you ever been to an auto parts store and seen air cleaner boxes that promise extra power and more torque than the factory filter? High flow air filters don't need to be changed as often as regular filters, and they offer better airflow and filtration of the air entering the engine. This can lead to increased horsepower by 3-5 HP and higher torque, as well as improved fuel efficiency. But do these performance air filters really work?YouTube's Engineering Explained decided to put them to the test. Jason from EE took a two-part scientific approach to proving the claims, using a dynamometer and real-world acceleration tests on his Subaru.
He analyzed four filters: a dirty material filter; a new, clean material filter; a new, inexpensive replacement filter; and a K&N high-performance filter. The results showed that moving from the factory dirty filter to the factory clean filter, to the low-performance filter, and finally to the K&N filter, produced a small power increase at each step. Real-world acceleration results confirmed these production increases; the fastest second-gear acceleration time was with the K&N installed. The aftermarket CarQuest filter was truly surprising, as it performed better than the clean OEM filter even though it cost less. This is because it allows a little more air to pass through than a standard paper filter - 0.14% more air than a standard paper filter in an independent real-world test.
High flow filters can also increase fuel efficiency by extracting cold air from outside of the car instead of hot air from inside the engine compartment. Cold air is denser and therefore will burn better, thus improving your engine performance. However, one problem that has been observed is that due to increased air intake, high-performance filters can expose the engine to more debris and contaminants. Whether you want to increase power, fuel efficiency, or simply reduce the hassle of regularly changing your air filter, a high flow filter can be a good option. But if you have an unshielded cone filter, you will only get good cold air flow to the filter when you go very fast - until then, you'll lose performance with a high-performance air filter.