Originally Posted by guy48065

You guys are getting a little carried away with the filter size thing. The Rzr runs great with a brand-new stock paper filter doesn't it? Does doubling the filter size get you any real increase in power? I doubt it could be measured. Some facts:
Stock 4x7 filter = 88 sq. in. of surface area
P181050 filter in UMP is a 4x10 filter = 125 sq. in. - A nearly 50% increase.
P181054 filter in BTI is a 6x12 filter = 339 sq. in.

So the Donaldson filter used by UMP is already a 50% improvement over the stock filter but it isn't for more power--it's to hold more shit. The stock filter holds a lot of shit, too, but the issue is how much of the nearly unmeasurable fine dust that gets through it.

Someone over at PRC posted some interesting filter facts many months ago. I don't know who, what or when and I'm not going to go dig it up but the essence of it was this:
Say Brand X filter traps 99.8% of 10 micron particles and is considered an excellent filter.
Brand Y traps 99.9% so it's only .1% better and probably not worth the bother, right? Wrong! It's 100% better because the amount that got through was 1/2 what Brand X passed. That makes Brand Y an amazing filter even though it would be very hard to measure or see such a small difference.

Originally Posted by keowee1

Well said.....i cant measure hp for sure. but i can compare. I raced a buddy of mine that got one about the same time.. i did a few times..we were about the same everytime.... put on snorkel and BTI and beat him by ALOT everytime.....later met MUDWIESER(another member) for a trail ride. great guy...never met him before... raced him that day. he has a gibson pipe and a fuel controler and we were side by side....he just bought the BTI/DFR because of it. can't tell you increases but can tell how my machined changed...if something comes out better please let me know...i will change!!!