In Reply to: K&N filter worth it?? posted by norman on September 19, 1999 at 20:18:43:
: the upgrade bug bites again. Do K&N filters improve performance? mileage? thanks
Nope, I would say that a K&N might give you the extra .0005 hp you need in racing/competition, but it's practically useless on the street (IMHO). The only practical advantage in having one is the ability to reuse the filter again and again. But BMW air filters are cheap anyway, so who cares? I tried a K&N cone filter out for a few months. It made great noise above 4000 RPM, but I saw no performance gains. What turned me off of the K&N was its poor filtering ability. At my next oil change, I removed the filter and found a filmy residue and thick cheesy substance lining the intake and throttle body. The K&N was letting WAY too much pollen and dirt into the intake. But it was designed to do this: more airflow = more dirt. Anyway, I took the darn thing out. It probably wasn't hurting anything, but I bet the additional debris in the intake would eventually shorten the life of the engine. I'd stick with the stock filter if I was you. If you want, you could modify the factory snorkel (behind the headlights) to make it a wider diameter, somewhat increasing airflow (and noise).
Please check the archives under "K&N" or "air filter" to see other people's opinions.
90 535iM, sharked, CCA