K&N Worse than Paper?

[ToeJam]

A buddy sent this to me today. He was looking at getting a K&N for his BMW, but found this on one of the boards he goes to.
http://bimmer.roadfly.org/bmw/forums...=338878&page=2

Interesting results. I can't seem to think of why a K&N would do worse than a paper filter? Any ideas?

[xoc]

I know this much crap gets past them...

[Antitree_hugger]

XOC is that with the K&N or Paper?

[Stormy]

Any chance that it's oil residue from the filter and not dirt?

[ChuckH]

Depends!

K&N filters are sensitive to proper oiling and use. Too much oil can cause problems with your sensors...too little will reduce filtration of small particles. Also, a K&N filter works better when it has some dirt in it. As far as Ian's pictures go, I don't believe that is any more dirt than would be found with a paper filter under the conditions we drive our trucks in. Only difference is that since a paper filter is dry, the dust goes straight into the engine. The K&N will allow some oil to get into the intake and the dust will stick to that, as shown.

As far as losing 15 HP, that's bullshit. You can't lose or gain 15 HP with any type of drop in filter unless it doesn't have holes in it or something. At most, you would see gains or losses of more around the 2-3 HP range which you won't even notice. Where you can lose 15 HP though is with an improperly placed cone filter. If a cone filter doesn't have a box around it to block engine heat, it will suck in hot air from the engine compartment instead of cooler air from outside. Colder air is more dense=better combustion. That's why cars feel more peppy in the winter time...they are.

Anyway, I wouldn't recommend a K&N filter to anyone who doesn't feel comfortable with the process of cleaning and oiling the filter. Not doing it right can cause a lot of grief and lost money.

[superjens]

So what's the trick with oiling it? How do you know if you've over done it?

[Kerensky97]

I've re-oiled them and it's really hard to tell.

For one thng the oil inthe re-charger kit isn't as red as the oil from the factory.

When you do re-oil it, do it in successive coats. It's easier to tell when the filter has enough oil because as its absorbed into the filter you need to put more oil on.
Pretty soon the oil doesn't soak in any more and you'll know that there is enough oil on it.

[OffroadX]

The hp gains are more percentage than anything. You would probably see 15 hp from a K&N in a big 300+ hp 5.9L V8, but no way you'll see it in a 170 hp 3.3L V6.

Brent

[xoc]

Originally posted by Antitree_hugger
XOC is that with the K&N or Paper?

That's with a K&N.

The white dusty stuff on the airbox is on the engine side. Very dry, and not oily at all. The stuff in the intake runner is gritty and oily.

I've run K&N's in all of my motorcycles for years, so I'm sure I'm cleaning and oiling it correctly.

[Kerensky97]

Originally posted by xoc
That's with a K&N.

I don't think that the powder is anything to worry about, stuff still gets through all filters.

I'm actually glad that its only fine powder that gets through, better than letting sand sized particles through.

[ozxterra]

Ive run K&N's in several trucks (GM and Nissan). They do work better with a little dirt on them. I have found the one for the XTerra is very sensitive to how its installed as the rubber around the outside can unseat and allow dust through the side. They are a good addition, particularly if you do a lot of miles. Id give em a thumbs up. Im not sure the performance gain is noticable though. I just like them. Recharge is fairly easy but to be honest I toss mine every 60,000 miles on the vehicles Ive owned ('coz I'm lazy).

[mudflap]

I quit running K&N's on my BMW's because of dust downstream even with K&N's sealing grease. I don't think that you will see that dust with a paper element. Will pull my M3's and the Xterra's filters for a look-see soon. Both are OEM paper.