I'm installing a HMF muffler and I want to install the best filter. I do mainly trail riding, going up hills, and doing mud. what is the best filter to get

 

Mud = wet conditions = Uni/Twin Air or some other type of foam filter.

 

You can not go wrong with a K&N and an outerwear or a nice two stage foam from Uni or Pro Design. I have had both types and have been more than satisfied with the performance of both foam or the gauze K&N. Supposedly if you are riding in very dusty areas, foam is supposed to be better. Well oiled, either have worked fine for me. Going to have to rejet with the added air your slip on and air filter will give your engine.

 

i would get either the k&n with outerwear or the uni foam filter both work well i have the k&n with outerwear

 

I run k&n's on our quads. On the mojave, it's exposed to the elements even though it's under the seat. It's been run through creeks and puddles with no problems[img]i/expressions/face-icon-small-smile.gif[/img] Just run an outerwear on them[img]i/expressions/face-icon-small-smile.gif[/img]

 

i know a guy who has a uni with an outerwear on it. i told he has way to much money laying around but he didnt care

 

If you want the best, as you say, you will get the most air flow (while still getting optimum filtration) from a cotton guaze filter (K&N). I would recommend spending a little extra for the Pro-Flow Adaptor kit so your filter will clamp on rather than relying on the airbox lid to hold it on.

Some will tell you that a foam filter (like UNI) will perform as well as a cotton guaze (K&N), but that is completely false. Of the three types of air filters (paper, oil treated foam, and oil treated cotton gauze), foam has the most restricted air flow while cotton guaze has the least restricted flow. Concerning filtering (based on particle restriction and air flow maintenance as filter get dirty), paper filters the worst, then foam, and cotton guaze the best.

Here is a third person research study, comparing the abilities of the three types of filters using name-brand examples.

~HoundDog

 

Yeah guys, if you read the signature its for a utility quad not a racer. Personally I believe that the foam filters perform better in wet and muddy conditions and are also a lot easier to clean out when you get it wet/muddy or submerge the quad. The minor flow increase availible by the K&N w/ an outerwear does not outweigh these concerns IMO, not to mention the foam is about half the price of the K&N filter itself, plus another 15 for the outerwear.

 

I would have to disagree. To me, the outerwear becomes the savior in wet/muddy conditions. It's extremely small diameter mesh stops extremely fine mud from ever reaching the filter and its water repellent nature has saved our grizzlies more than once from a soaked filter. We run alot in deep river crossings and floating a bike is nothing unusual. I have yet to see an instance where a foam filter dried out quicker than a properly oiled K&N. Like he said... JMO... By the way, there's more than a "little" difference in metered airflow between a foam and cotton guaze filter (see article above^).


~HoundDog

 

I've read the article you posted, the flow change on this machine would be within the margin of error on any dyno. That article is no more unbiased than any other and there are not adequate controls.

The outerwear has nothing to do with the K&N filter, you can put an outerwear on any filter including a foam one. They are used because the K&N type are prone to let finer particles through and they perform poorly in wet conditions so the outerwear was needed to even the score. If you have the time to let your filter dry then thats one thing, but try ringing out your K&N...