For years we've been saying things like, "There's no such thing as too big an air cleaner" and "Run a tall element or double-stack two filters to avoid a restriction." But recent engine testing by Car Craft and Westech of a variety of free-flowing K&N air cleaners on a Comp Cams-equipped, 520hp Chrysler 448ci engine indicates the average street machine can actually scrape by with much smaller filter elements than previously believed.
We tried various new 14-inch-od open-element K&N units ranging in height from 2.25 to 6 inches. All the elements were tested with standard (no-drop) bases. The 2.25-inch unit was also tested with a 7/8-inch dropped base that could offer additional hood clearance in tight installations. For laughs, we also ran a tiny 3x7 K&N designed for the really space-impaired.
It turned out the joke was on us. The engine didn't care what air cleaner was thrown at it. All units tested made about the same power and torque. For example, peak power ranged between 518 and 522 hp, which is within the dyno's 1 percent error margin. The peak torque rpm point and peak power manifold vacuum reading tended to move up a hair with some of the smaller elements, indicating the beginning of incipient restriction, but the overall averages were…about average.
This engine needed about 585 cfm of airflow to make its 520-odd horsepower. According to the way K&N rates its filters, that should have required an air cleaner in between the 14x3 and 14x4 units. Obviously, K&N's flow ratings and recommended filter sizing methodology is extremely conservative--but in the real world an oversized filter provides a safety margin because it's more clog-resistant. Still, in an emergency, a small unit will do the job if serviced frequently. And K&N filters are washable and reusable, so it's still a decent investment in your engine's health.
Check out the individual air cleaner links below for the details....
