K&N vs. Stock vs. UNI and others


20 replies to this topic
  • saccityfire

Posted January 02, 2010 - 02:05 PM

#1

Just wondering what you guys opinion is of the added benefit of going to an aftermarket air filter after getting the "full system" exhaust for my 09 YZ450. I currently run a stock filter and I have noticed huge gains in power but as usual, I want more! Thanks.
:moon:

  • FinchFan194

Posted January 02, 2010 - 02:40 PM

#2

I would steer clear of a K&N but I have never noticed a major difference in foam air filters as long as its dual stage thats all that matters to me.

  • grayracer513

Posted January 02, 2010 - 04:04 PM

#3

Read:

http://www.thumperta...541#post4782541

  • Wes Woodin

Posted January 04, 2010 - 06:40 PM

#4

Just wondering what you guys opinion is of the added benefit of going to an aftermarket air filter after getting the "full system" exhaust for my 09 YZ450. I currently run a stock filter and I have noticed huge gains in power but as usual, I want more! Thanks.
:moon:

I would run a uni, because it is a two stage filter that is the easiest to clean. The twin air is fused together so it is harder to clean and harder to get even distribution of oil between the filters, unlike the uni. Uni you can take apart do your work then put together the grease.

  • grayracer513

Posted January 04, 2010 - 07:23 PM

#5

The twin air is fused together so it is harder to clean and harder to get even distribution of oil between the filters, .

This statement puzzles me since the only time a foam filter is correctly oiled is when the oil is thoroughly worked through the entire mass of the filter foam. I know I have no problem doing that with my Twin Airs.

  • Family Man

Posted January 05, 2010 - 12:33 AM

#6

I really like Twin Air too. They last alot longer than a glued filter, which end up comming apart at the glued seems.

  • cwcarter

Posted January 05, 2010 - 02:54 AM

#7

+1 on the Twin airs. Been using them for 20 years.

  • saccityfire

Posted January 05, 2010 - 09:09 AM

#8

Thanks for all of the input. I guess what I'm looking for is whether or not there is any performance difference with the aftermarket vs.the stock (which is a dual layer foam filter). I understand that the oil is what traps the dirt. Gray, you and I have the same filter cleaning and oiling process currently.

Are the aftermarket filters better than stock? If yes, It sounds like Uni or Twin air are about the same in quality by all of the posts here.

  • grayracer513

Posted January 05, 2010 - 11:21 AM

#9

I guess what I'm looking for is whether or not there is any performance difference with the aftermarket vs.the stock

There are all kinds of claims made, of course, but I don't know of any documentation either way. The main thing to me is that the Twin Airs seem better made and more durable.

Are the aftermarket filters better than stock? If yes, It sounds like Uni or Twin air are about the same in quality by all of the posts here.

Both those are top tier products. I use Twin Airs because I get a deal on them, and they are as good as any other you can buy.

Dual layer, or dual density filters are a little bit of a gimmick, but they work fine, so it's not a real problem. Basically, a foam with larger pores is more open, and resists air flow less. It will also be more capable of holding larger amounts of dirt without restricting air flow, but is less capable of trapping fine dirt moving at higher speeds. A foam with smaller pores has the opposite properties.

To understand this, you first have to understand, as you said, that it is the oil that traps the dirt. The foam itself would allow some really very large particles to wiggle right through. The foam is a matrix of interconnected bubbles (cells, more correctly) that form indirect pathways for the air to move through it. As the air passes through these cells, it has to weave its way through a "web" of foam membrane that is (or should be) coated with a fairly deep layer of sticky oil. Air and dust move though this maze together, but as the air is forced to turn to pass around the foam membrane, the inertia of the heavier dust particles carries them straight ahead, and they collide with the oil coat and stick there, if all works well.

Here's where the oil becomes even more important. If the oil is only very thin, or is not very tacky, it can only hold the dust particles that will cover its exposed surface, and may release them into a high velocity air stream. But if the coat is deeper, and the oil stays wet and tacky, it can completely absorb smaller particles, wetting them entirely over, and expose oil to the next one to hit the same spot.

When this works right, dirt builds up on the oil coat. When the oil coat can no longer absorb more dirt, the dirt moves farther down into the element, where, if it was oiled correctly, there will be still more oil to stick to. But eventually, one or more of three bad things will happen:
  • Either all of the available oil coat will become saturated with dirt, and the element will no longer trap anything,
  • The dirt build up will be such that it begins restricting air flow,
  • Because of the air flow restrictions caused by the dirt buildup, the increased pressure difference across the element will begin to pull dirt out of the element and into the engine.
Cleaning frequently oiling correctly are therefore the absolute most important things about an air filter.

Having two layers of foam at two densities is effective in that it lets the exterior of the element collect a lot of dirt without clogging, while still providing finer filtration at the interior levels. In truth, this could be achieved by selecting the optimum gauge of foam media for the whole filter, achieving a balance between coarse and fine, which is why I said dual layer foam is a bit of a gimmick. Using dual densities does, however, allow the same mix of foams to work well for a wide variety of applications.

  • thumpinberry

Posted January 05, 2010 - 11:44 AM

#10

i use twin air and uni they are both good filters.i like to use a uni when it is real dusty.not much dirt gets by the outside filter.and it is easier to clean!!

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Wes Woodin

Posted January 05, 2010 - 08:09 PM

#11

This statement puzzles me since the only time a foam filter is correctly oiled is when the oil is thoroughly worked through the entire mass of the filter foam. I know I have no problem doing that with my Twin Airs.

Twin airs have different density foams. That are glued or fused together. I will tell you that I take my uni's apart to clean them and I will also say that I have had a tough time on several occasions getting the embedded sand out of the outer filter. I would sometimes have to do it from the inside. If I was using a twin air, there would have been no way to get it out when the filters are glued together, unless I ripped them apart. Just my experience.

The fastest Motocross and supercross on earth uses Uni for a reason:worthy: James Stewart on that sweet 2010 YZ450f:worthy:

  • grayracer513

Posted January 05, 2010 - 08:49 PM

#12

... I have had a tough time on several occasions getting the embedded sand out of the outer filter. I would sometimes have to do it from the inside. If I was using a twin air, there would have been no way to get it out when the filters are glued together, unless I ripped them apart. Just my experience.

The fastest Motocross and supercross on earth uses Uni for a reason:worthy: James Stewart on that sweet 2010 YZ450f:worthy:

I have had no problem cleaning Twin Airs, either. Don't know what to tell you.

The "reason" Stewart uses Uni's has nothing whatever to do with a choice made by him, and they have nothing to do with him being fast. If you don't see a UNI sticker on the bike, the San Manuel crew chief decided to use them because he likes them. If you see a sticker on the bike, that sticker and the filters are there because UNI paid the most.

  • cwcarter

Posted January 06, 2010 - 03:21 AM

#13

The fastest Motocross and supercross on earth uses Uni for a reason:worthy: James Stewart on that sweet 2010 YZ450f:worthy:


I'd use them too if they were given to me.:moon:

  • saccityfire

Posted January 07, 2010 - 12:14 PM

#14

Thanks for the info Gray and others. I guess I'll just get Uni or Twin, whichever is cheaper.

  • FinchFan194

Posted January 07, 2010 - 04:36 PM

#15

I am gonna go Twin from now on. My UNI's have been falling apart from the solvent I was using(kerosene)

  • DrThumper

Posted January 08, 2010 - 01:43 PM

#16

I have K&N's on everything I own.
On my YZ I think it really helped the low end trackability and torque.
I have heard about them being hard to clean, or at least, cleaning is really important for proper performance (I believe Grey will back me up on this one).
But my personal experience with K&N is nothing but stellar.
I don't seem to have a problem cleaning and re-oiling.
I think a good hint on proper oiling is to oil the inside slightly too, that way the pleats that are folded on the inside get some.

  • grayracer513

Posted January 08, 2010 - 02:13 PM

#17

I have heard about them being hard to clean, or at least, cleaning is really important for proper performance (I believe Grey will back me up on this one).
...I think a good hint on proper oiling is to oil the inside slightly too, that way the pleats that are folded on the inside get some.

As I pointed out, the downfall of K&N filters is in the difficulty involved with oiling them correctly. Just as with foam media, the ability to filter is completely dependent on the media being oiled through, from outside to inside, not simply coated on the exposed surface. Since foam can be squeezed and kneaded, this is relatively easy to do. Not so with pleated, layered gauze elements.

K&N's that are properly prepped do actually filter better with less resistance than foam, but they way most people oil them, they don't work any better than a wire screen, and they don't have the dust holding capacity of foam either.

  • roylo

Posted January 09, 2010 - 03:22 AM

#18

Just wondering what you guys opinion is of the added benefit of going to an aftermarket air filter after getting the "full system" exhaust for my 09 YZ450. I currently run a stock filter and I have noticed huge gains in power but as usual, I want more! Thanks.
:moon:



I went to the 'normal' Twin Air after the standard YZ filter started to show a bit of wear and tear and am happy with it. I dont think you will notice a performance increase though.

I have tried the thinner Twin Air 'high flow' filters they use in the high flow kit and they may flow a bit better but they definitly let dust through. I always smear some filter oil on the inside wall of the air boot and found small amounts of dust particals there when using the thinner filter but not with the standard Twin Air one.
I would stay clear of the thinner type foam filters.

  • moto278

Posted January 09, 2010 - 04:31 PM

#19

I have K&N's on everything I own.
On my YZ I think it really helped the low end trackability and torque.
I have heard about them being hard to clean, or at least, cleaning is really important for proper performance (I believe Grey will back me up on this one).
But my personal experience with K&N is nothing but stellar.
I don't seem to have a problem cleaning and re-oiling.
I think a good hint on proper oiling is to oil the inside slightly too, that way the pleats that are folded on the inside get some.


i too have a k&n on everything i own. they do take a lil longer to clean than a foam filter but i do love the durability and performance from them. on my 05 250f it improved the throttle a bit and i could tell the motor was breathing considerably better. and as soon as they come out with one for my 10 450 ill grab one as well. ive never had problems oiling them, but next time ill try oiling inside as well to see what that does. ive never had an issue of anythingn getting past the filter but no harm in tryin a new method

  • Wes Woodin

Posted January 10, 2010 - 07:20 PM

#20

I am gonna go Twin from now on. My UNI's have been falling apart from the solvent I was using(kerosene)

Well that's why! Solvent. Use PJ1 Foam Filter cleaner. It smells good and is water soluble.
Uni, PJ1 filter cleaner and bel ray foam filter oil.......... The winning combination! IMHO





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