carock said:
"In the years I ran my dyno business, we replaced the original air filters with direct K&N replacements at LEAST one hundred times in back to back comparison tests with the original factory filter. In ALL BUT ONE case, the K&N filters made LESS power than the stock filter. I remember the only car that showed a power improvement was the Volkswagon Corrado with the supercharger. I was never impressed with these filters. It goes to show that measuring pressure drops is NOT the same as measuring power. K&N filters have measured lower pressure drops than factory filters, but this does not translate into more power. By the way, there are a lot of other examples where improved air flow measurements or pressure drops actually reduced power."
I've been following the K&N air filter debate for two or three years on this and on 3 Ford Ranger forums and a Subaru Forester forum, with great interest. I think that this is the best argument I've seen for the claim that the K&N does not increase power, assuming that what he says is true, and I have no reason to believe that it isn't. That said, I'd really appreciate it carock if you would elaborate on what you said. Was it a truly professional shop, with a quality dyno? Were the tests run under controlled conditions? For example, run on dyno with paper filter, immediately switch to K&N, and immediately run on dyno again? No gain in EITHER hp or torque? Do you know if other dyno shops also rarely or never measured any power gain, and whether any dyno shops DID measure a power gain?
I'm running the K&N in two 2003 vehicles. I've become increasingly sceptical the past year or so of the value and advisability of doing so. Besides your post carock, I've been very interested in the often-posted link on what appears to be an excellent independent study of the air flow of the K&N and other types of air filters, a study that is not at all favorable toward the K&N. I'm about ready to switch back to paper and your post might just have tipped me over that edge.