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K & N Airfilter opinions

Discussion in 'Bling and Appearance' started by BJR, Jun 17, 2007.

  1. I'm thinking of fitting a K&N airfilter in my GSXR but, are they worth it? do they make any difference? Let me know what your opinions are........

  2. I put a K and N in my stock Honda vt 750 cruiser and immeadiately noticed an improvement in acceleration.

    I also put a K an N in my Yamaha TTR250 with no noticable difference.

    Some swear by them, others don't.

    If you are goingto ride in "dust free" environments, the Kand N are fine.

    Good thing is at service time just clean and replace. Esy.
  3. in my opinion K&N's improve performance a little on some things, but not everything. although thats not why i like them.
    If you have a K&N you will never have to buy another air filter you can just clean it at recomended intervals. its awesome
  4. Fitted a K&N to my old VTR firestorm and got a noticable improvement along with re-jetting and modded pipes ran great.

    Would recommend one for sure.
  5. Never tried them in a bike but have them in both my cars and they make a difference - not so much in peak power but there's a noticeable improvement in engine response and mid to low-range torque. They're also the only aftermarket filter I know of that is proven to provide just as much dirt protection as OEM - so there's definately no downside there.
  6. Love my K & N Air & Oil filters for all of the above reasons!
  7. i found that it makes the bike rev more easily and smoother.
  8. With or without a Power comannder??
  9. remember though guys, the reason that K&N filters flow better is because they filter less.

    If you plan on keeping your bike in a dust free environment and not keeping it too long all is good. Otherwise expect higher engine wear.....

    Like free lunches, there is no free horsepower in life guys.
  10. And you're basing this on what exactly? All K&Ns are tested to ISO standards, all are around 97-98% efficient (or higher). Yes some other filters may be more efficient at stopping dirt (though obviously only by 1-2%). But then there are filters that run as low as 92-93, and since they don't actually give any results or guarantees you'd never know.
  11. Don't forget uni-filter. Australian owned and run and cheaper.
  12. A K&N did bugger-all for the Hornet 900, dyno verified. I wouldn't bother.
  13. I highly recommend a Pipercross filter, they are made in England and are guaranteed for life. The best thing about a Pipercross foam filter is that the flow rate does not significantly change when the filter gets dirty, unlike a cotton filter (eg K&N, BMC & DNA).

    For sports bikes you can buy an even less restrictive (read, more performance) race version.
  14. Another forum I was on (in another life) had an engineer who did a hell of a lot of testing on K&N products and posted some information about their lab's testing on volumes of dirt injested.

    Pretty much any coarse weave material is going to be bad - whether it's K&N, unifilter or anyone else.

    there are better filters and worse. Up to you to decide how much longevity you'll swap for performance.

    remember, what works on the racetrack is power- the motors are rebuilt after every race anyway and they dont care about life expectancy over anything beyond race distance.
  15. I think you are overlooking the role of the tacky oil in the equation. Paper filters don't have this and have to be a finer weave as a result. You can achieve a courser weave for the same filtration if you have a tacky substance collecting the dust.
  16. So, "mystical dust attracting oil"...

    Not overlooking the tacky oil at all, i just have a basic understanding of physics.

    If there is a little bit of oil on the filter, all you get is where there are drops of oil (a very small proportion fo the total surface area) it *may* catch some of the dust.


    Most likely it wont even do much of that, since those areas where there is oil concentrated will have lower airflow and thus most of the air and dust will just bypass them. Basic flow dynamics.

    Alternatively, If there is more oil in the filter, then it's harder to breath through oil than a paper air filter. Try it some time and tell me - I'll put my mouth to the paper filter and you can suck through the oil.... we'll see who passess out first.

    If you put enough oil on the filter to actually have any noticable filtration effect, you lose all your performance, and screw up your mixture, and suck down heaps of filter oil into your intake. not good for your motor either.

    You can't guarantee an even consistency when you apply the oil no matter what you do. You'll still get points where there is little oil and thus you get ineffective filtration, and over time the oil gets drawn to the bottom of the filter so your filter doesnt filter at the top.
  17. Did he actually mention the testing standard used or at the very least the method and particle size distribution of the test sample - because if not then frankly their results don't mean crap. I've seen plenty of manufacturers that give data "proving" their filters are the best but when you look at their test method (if they'll tell you it at all) you usually find they've biased the test to achieve the result they want ie using a disproportionately large amount of material within a certain size range. This may show a certain filter results in less dirt "ingested" but not all size ranges are particularly harmful to an engine - so the filter that lets more material through (in the biased test) may still be stopping more of the material that actually causes damage. One look at a paper filter under an electron microscope and you'll soon realise just how inefficient their design is. The random nature of the fibres means that they're always going to be a compromise between something that has numerous holes but lets air through (like a car filter), or something that blocks everything but chokes very easily (like a lab filter).
  18. Clearly you've never had one of these things in you hands. The oil is tacky and does cover the entire weave if you load it properly.

    Also, your theory on the oil only catching a small proportion is incorrect. The air flow within a filter like this would be very turbulent. The result is most of the dust would tend find it's way near the surface of the weave on the way though.

    You just need some way of keeping it there. The tacky oil does that.

    These things drop off quite markedly in performance if you don't clean them, which is proof they do work.
  19. Omg... I used to work as a bike mechanic, I've owned a string of trail bikes, pod filtered road and race two strokes and you dont think I've ever touched a K&N or Unifilter?

  20. Also the other thing to cosider is how often you clean a foam filter against how often you replace a paper one.

    I clean and reoil my foam filters EVERY oil change, dirt bikes 500k (every ride if dusty conditions), road bikes 5000k.
    When i did the 75000k service on the VFR recently (only had bike about 18months) i checked the air filter and it was filthy (yeah should have checked it when i bought the bike) and it had 25000k written on it :shock: FARK, hasnt been replaced for 50000k.
    So i replaced it with a K&N and will clean it every 5000k.