K&N air filter

I just put a K&N air filter on my 99 R110R and it appears to make a huge difference. Anyone experience the same or is it just in my head? Any one have anything bad to say about these filters?

I have a K&N, it came with the bike. (1150 GS) Several wrenches said they are fine except in very dirty enviornments. If riding a lot of dirt road or sand they said to use a stock filter as the pour size is much smaller on a stocker. There have been a few times I found a little bit of grit inside my airbox, inside the filter. That's not a good situation.

performance wise; I find it odd that K&N doesn't have dyno information plastered all over their web site and ads. Makes me wonder

If little old me can think of it, why haven't they??

wanderer said:

Several wrenches said they are fine except in very dirty environments. If riding a lot of dirt road or sand they said to use a stock filter as the pour size is much smaller on a stocker. There have been a few times I found a little bit of grit inside my air box, inside the filter. That's not a good situation.

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What Wanderer said.
Be careful in dusty areas, as the K&N does let more air through, they will also let more dirt in. I have one on my truck and it made a lot of difference in torque and HP. On a bike I doubt if it will make a big difference over the stock paper filter. If you want to increase power, than an exhaust and computer mod are your best bet.

R1100RinOR said:

I just put a K&N air filter on my 99 R110R and it appears to make a huge difference. Anyone experience the same or is it just in my head? Any one have anything bad to say about these filters?

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Pretty common topic; I've seen this discussed on the BMW-Tech list, the GS list, and elsewhere on cage lists I'm on, including both enthusiast-type discussions as well as professional tech discussions.

I don't have specific experience with a K&N in an oilhead but I can cite some K-bike info. (1) Brian Curry and Don Eilenberger did a dyno study on air filters and other performance tweaks on a K bike several years ago. Writeups are available on the IBMWR site. They found NO, repeat ABSOLUTELY ZERO, improvement with a K&N. (2) Personally, when I bought a used K100RS it came with a K&N. I put in a stock BMW paper filter and certainly could not discern even the remotest difference with my butt dyno.

The real issue from a performance standpoint is whether the stock filter is actually a choking point or not. Again, I can't claim I've done dyno work on an oilhead, but my understanding is that motor vehicle engineers the world around have figured out how to make an engine breathe very effectively with a good old paper filter. The likelihood that BMW screwed up the intake design and accidentally choked off the engine with the stock filter, such that you'd find a "huge difference" as you say, is very close to zero probability in my book. (This notion is certainly supported by Curry and Eilenberger above.) Is it possible your previous filter was horrendously clogged? That's the only scenario that makes sense to me.

Beyond performance, there is certainly the camp that believes the oiled-gauze fabric (K&N) has pore openings so much larger than a paper filter that filtration effectiveness has to be much lower. K&N's marketing materials throw smoke and mirrors at that notion, trying to make you believe there's some sort of magic that helps small particles get trapped even as they fly through relatively large openings. Beyond that, there's two more questions that are nearly impossible to answer - one, just how much particulate is in the environment where you are operating the engine; and two, how many particles, how big, for how long, before there is any detectable engine damage? Most people who care about engine longevity prefer to err on the side of caution when those two questions are posed.

Then there's economics. K&N's are washable and reusable. Over a long period of time (maybe VERY long) they might be more economical. As long as they don't trash your engine over that same long period of time, of course.

And finally there's Zen and the Art of Motorcycle Maintenance: The K&N gives you something to futz with if you're the type who laments the passing of points and condensers and other mechanical bits that you used to be able to get up close and personal with.

soffiler said:

And finally there's Zen and the Art of Motorcycle Maintenance: The K&N gives you something to futz with if you're the type who laments the passing of points and condensers and other mechanical bits that you used to be able to get up close and personal with.

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There is something about a rider bonding with his/her machine.

Dunno if this is really true, but I heard somewhere that the stock paper filter performs more consistently over its life than a K&N does between cleanings.

With what stock filters cost though, the economic argument could get compelling. The BatBike's filter runs about $30 for the stock item.

Hi, All,
K&N air filters also are more difficult to install correctly in my K1100LT's or Harriet's K75's. I'm still running stock filters for that reason and the results of the Curry/Eilenberger dyno runs. The K&N frame is of a softer, more pliable material than that of the stock filter and is more prone to leak around the edges. That said, if anyone wants a K&N to fit a K75/100/1100, I have one (used, cleaned and re-oiled) for $25, shipping included, anywhere in the lower 48.

K&N

I used a K&N for 132,000 on my '96 R1100RT. At the end of that time oil comsumption was nill and compression and bleed-down tests were within factory specs.

Randy

I've heard of several folks that have used K&N air filters on bikes with relatively high miles with no problems. One thing that seems common with folks with relatively high mileage machines is regular maintenance, including oil changes every couple of thousand miles.

There have been several more-or-less scientific studies of the filtering capability of K&N filters. These studies seem to conclude that the K&N will allow more fine particulate matter to pass through the filter than will a stock paper filter.

Many of the BMW Airhead gurus have indicated that they will not use K&N air filters. One could search the Airlist archives to find specific postings on the subject.

Some links with more info and test data follow:

http://www.ibmwr.org/otech/airfilter.html

http://faq.f650.com/FAQs/KN_Air_Oil_Filter.htm

http://www.bobistheoilguy.com/airfilter/airtest1.htm

http://motorcycleinfo.calsci.com/Filters.html

http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm

http://www.knfilters.com/testmethod.htm

http://offroadpakistan.com/bitsnpieces/tech/how_well_do_kn_air_filters_work_1.html

http://www.4by4connection.com/airfilters2.html

http://www.hotrod.com/techarticles/70738/

For what it's worth,when it comes to after market filters, you should check out BMC Air Filters

They're used on some of the Superbike and Supersport racing teems as well as Farrarri, BMW, Mclaren, and Toyota in Formula one racing.

Just to add to the mix - I did have a K&N on my old K1100LT, but when I traded it in, the GS had the OEM paper. Since I work part-time at a shop that is primarily dirt-oriented, I looked at what off-road machines use. I invested in a UNI oiled-foam filter, only about $12, and cleanable. So far, in 2 years, it's been doing well.

After reading all the tests done on K&N vs. stock...I'm back to using a stock filter after many years of K&N use.

I read a few articles of independent tests from the web, and it seemed that both work great. The OEM proved to protect against the fine particulates better than the gauze types for obvious reasons. I chose to stay with the OEM filters just because they work so well, and because dust can be plentiful on my fave trails. Also because I don't want to carry the filter oil with me on long trips. I can gently shake the OEM filter just fine to shed debris.

At the end of it all both will work and as posters have already attested to high mileages on K&Ns w/ no reported observed damage it is hard to arrive at any other conclusion than it is just what you prefer. After riding dirt for some years though, just remember to oil the darn thing...lol.

K&N

After many years of use in all my autos and bikes, I have never had a problem, and have been very happy. More noticable improvement in the autos, but since I am a street bike guy, dont forsee, nor ever had a problem. Just do the maint. every other summer.