October 29, 200520 yr Im lookin for a high performance air filter. So which one's the best? HP increase? MPG increase?
October 29, 200520 yr I just replaced my air filter with a K&N. Those are the best all around air filters that you can buy, you never will have to replace your air filter again.
October 29, 200520 yr This is for a '99 Legacy GT? You will note that plenty of people make claims about performance or mpg improvements for K&N and other after-market air filters. But I've yet to find one who carefully documented the performance and MPG of the vehicle before and after the change. I'd expect the mpg improvement to be approximately zero. And the performance improvement at public road speeds to be approximately zero. With the importance that buyers place on the EPA sticker #'s and 0-60 performance, if they were better they'd be OEM. The trade-off in engine wear due to particulate matter and increased noise aren't worth it.
October 30, 200520 yr Ranger is right. If they were so great, they'd be installed at the factory. If Subaru could gain event 1 or 2 MPG AND increase HP by even 1 or 2% by installing a so called "low restriction" air filter don't you think they'd do it ? Ditto for the so called "cold air intakes".
October 30, 200520 yr ALlow me to introduce you to the search button .... do it on airfilters. I just did this yesterday and posted it in a long thread, and sorry folks not up to it again. My pain pills for my back are giving me a nice ride. Detailed test on GM duramx Deisel and aftermarket filters. Guess who came out on top...the OE airfilter. any filter that has better air flow has to have larger poors, and let more air in, hence more dirt. The pistons can handle it, but the fuel injectors cant, nor can any sensors down stream from the airfilter. nipper
October 30, 200520 yr I agree with Nipper. Sure you might get 1-2hp by running a less restrictive filter but for longevity it definately isn't worth it. On a side note I've run my XT6 without a filter vs with on autoxing and have had a better time every single time when there was a filter on. (the engine is toasting slowly so I'm not real concerned about airborne diseases getting past!!!
October 30, 200520 yr Chip, noise and emission regulations limit the factory options. If oiled gauze is so bad, why does STi produce one? And many Subaru's have CAI stock. The older models draw air from the fender, interim models from behind the headlight (dubious CAI), and newer models suck from the bonnet/hood lip.
October 31, 200520 yr The factory filter will filter out smaller particles then the KN, so for longevity the OEM would be best. I bench flowed the air box and intake on a flowbench, you get 3 cfm tops, which on a good day might get you 1 hp. My opinion, don't waste your money. the reason everyone claims that they got so much hp from an air filter, is because they don't want to feel like the idiot who just spent 70 bucks on somthing that didn't do anything. just my .04
October 31, 200520 yr Author The factory filter will filter out smaller particles then the KN, so for longevity the OEM would be best. I bench flowed the air box and intake on a flowbench, you get 3 cfm tops, which on a good day might get you 1 hp. My opinion, don't waste your money. the reason everyone claims that they got so much hp from an air filter, is because they don't want to feel like the idiot who just spent 70 bucks on somthing that didn't do anything. just my .04 Thats a bummer, I wanted the hp.
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