[Hoiho]

Given the bad rep K&N and other reusables often get for poor particle filtration; I'm suprised that so many folk install these things in place of the stock filter.

Are most folk at the drag strip each wkd trying to eke out every last micro-hp, or have they just turned a blind eye??

Discuss 

[RalphG]

I've used K&N filters for over 30 years.   No inclination to stop.

Ralph

[6504me]

Most problems with K&Ns are the loose nut in front of the filter.

Drying them with compressed air is a BIG no-no. Over oiling is another mistake lots of people make.

Properly cleaned and oiled K&Ns give good service on the street and save $$$ in the long run.

[NVDucati]

Given the bad rep K&N and other reusables often get for poor particle filtration; I'm suprised that so many folk install these things in place of the stock filter.

Are most folk at the drag strip each wkd trying to eke out every last micro-hp, or have they just turned a blind eye??

Discuss 

Honestly, the bad rep that K&N has been given over the last couple of decade has me stumped.
Anyone who really wants to find out about air filters and compare the various types and brands should start with learning about the "Frazier Permeability Test ".
   In respect to everyone's time and because i don't know how many people care I'll just drop a couple of URLs and  snipits as a starting point.
http://frazierinstrument.com/products/fap/fap-description.html
"The Frazier Precision Instrument Company manufactures a Differential Pressure Air Permeability Instrument in three models.  The First model, The Low Pressure Instrument  was developed by the National Institute of Standards and Technology for measuring the air permeability of textile type materials and is the acknowledged standard of the U.S. Government and the U.S. Textile Industry. Frazier, in conjunction with the  U.S. Air Force developed a second model, the High Pressure Instrument on the same principle as the Low Pressure Instrument, but designed it with a much greater versatility of use through its higher attainable air flow and differential pressure. The third model is the Frazier 2000TM.      Model Comparison Chart

The Frazier 2000® is the next generation of Frazier Differential Pressure Air Permeability Instruments.  This new instrument builds on Frazier's well-known reputation and implements electronic pressure sensing as well as computerized logging and manipulation of the electronic measurements.  The Frazier 2000® brings a whole new era of reliability and productivity to the field of permeability testing and measurement.  The Frazier 2000® has all the same features of High Pressure Permeability Instrument in addition to those listed. (Additional Information about the Frazier 2000) The Frazier 2000 requires the use of a Windows based personal computer not included."

https://www.knfilters.com/efficiency_testing.htm
"K&N operates an in-house filtration test lab with two different testing machines built in consultation with Southwest Research Institute, one of the pre-eminent testing companies in the world. Most of the filtration testing we perform on our air filters is performed in our lab that operates on a year round basis. Occasionally, we send air filters out for testing with an independent lab, either to confirm our in-house testing or to reduce the capacity requirements on our lab.
   We perform tests of filters both in the factory air box and in SAE/ISO recommended test housing fixtures. Our goal is to design filters with the maximum possible airflow achievable while providing guaranteed engine protection.
   Our actual air filters when tested generally demonstrate a cumulative filtration efficiency of between 96% and 99%. All this testing we do allows us to guarantee our air filters provide all the protection your vehicle will ever need.
   For a more technical explanation of our filtration test stand procedures see our Efficiency Testing Procedure."
https://www.knfilters.com/efficiency_testing_procedure.htm

https://www.totalmotorcycle.com/downloads/aftermarketfilters-Airfilters#PAPER

[Karl Fenn]

Well to be honest it's the cost that stops me using them, and also l am not convinced it filters particles and microns as well as the stock filters.

[zimmemr]

Given the bad rep K&N and other reusables often get for poor particle filtration; I'm suprised that so many folk install these things in place of the stock filter.

Are most folk at the drag strip each wkd trying to eke out every last micro-hp, or have they just turned a blind eye??

Discuss 

 I used K&N filters on most of my dirt trackers, sometimes with a "sock" if it was dusty, more often without one for at least thirty years and never lost an engine due to dirt ingestion. I'd venture to say that among dirt trackers the K&N is probably the most popular filter out there.

 I can also tell you that it's an extremely popular filter in the construction industry. Lot's of earth moving and farming equipment have them installed, normally with a pre-filter, which is standard practice. If your excavator or combine goes down, it's expensive and a huge PITA for everyone involved so nobody skimps on filters,  I think the popularity of the K&N in that instance would speak volumes.

Lastly given the size of the company you'd have to think that they must be doing something right to sell all of those filters.

For the record I have one in my Interceptor and my DR400EZ. And will install one in my Himalayan as soon as it needs one.

[GravyDavy]

Well to be honest it's the cost that stops me using them, and also l am not convinced it filters particles and microns as well as the stock filters.

I don't know if this is still the case, but they used to advertise airflow measured with a new, clean filter, and filtering effectiveness with a very dirty one.  They didn't specify filtering effectiveness of a new one with all of the big holes that you can clearly see light through, only one that was approaching being clogged.

Once I noticed that, I never looked at them again.  Does anybody know if they are publishing the micron rating of a new, properly oiled one?

[Jack Straw]

For the last 25 vehicles I've owned I don't think Ive given more than 90 seconds of thought to elfin' air cleaners.

[NVDucati]

I don't know if this is still the case, but they used to advertise airflow measured with a new, clean filter, and filtering effectiveness with a very dirty one.  They didn't specify filtering effectiveness of a new one with all of the big holes that you can clearly see light through, only one that was approaching being clogged.

Once I noticed that, I never looked at them again.  Does anybody know if they are publishing the micron rating of a new, properly oiled one?

Geez ... (you're just pulling my leg? Right?)

[GravyDavy]

Geez ... (you're just pulling my leg? Right?)

Unfortunately, no.  Those were really their claims in ads and magazine articles. Bear in mind that I'm talking about sometime in the 70's when they were still a new innovation.  A whole lot may have changed since then, but after that first impression I've literally never looked at gauze filters again. I'm not a performance or ultra-mileage rider, so buying a new paper filter every few years just isn't an issue for me.

[Effektor]

Seems like most if not all the "bad rap" they get is from people using testing data of dubious relevance while the people who have used them for decades like them and have had no issues. I don't worry about using them and don't get paid to convert others to their use, so I don't worry about them using them either.

[BlackIce619]

This is a great discussion. I have always used reusable air filters on all my vehicles. It probably has saved me money in the long run for sure, but am going to hang out in this post to see what everyone thinks. If the complaint is about K&N, then I am glad I have the S&S version 

[NVDucati]

Unfortunately, no.  Those were really their claims in ads and magazine articles. Bear in mind that I'm talking about sometime in the 70's when they were still a new innovation.  A whole lot may have changed since then, but after that first impression I've literally never looked at gauze filters again. I'm not a performance or ultra-mileage rider, so buying a new paper filter every few years just isn't an issue for me.

No worries GravyDavy. I was reacting to your question “Does anybody know if they are publishing the micron rating of a new, properly oiled one?” when I had just, minutes before, posted links to specific, independent information.

I truly get it that none of this might matter, at all, to some folks. But I guess I could have also mentioned that the FAA has certified K&N filtration for aircraft. One supplier cites:
“K&N re-cleanable air filter media
Up to 50% more air flow with the same dirt holding capability
NO ADS (Airworthiness Directive) 
Increased horsepower
Reported fuel savings of .3 to .5 gallons per hour”
A third to a half gallon saved per hour is a big deal for pilots. Not so much as a money saver but for the effect on available range. (from 6000ft you can’t just push your plane to the next gas station) Even if one only looks at it from an ecological viewpoint including the notion of the disposables… it is not just a drag strip thing. Don’t know if that matters.
   Last, how often one changes a air filter is subject to a lot of considerations. One consideration should be that as any air filter gets covered with dust, it creates a vacuum on the fuel intake side. Paper filters are more prone to eventually suck the particles right on through much sooner.

[Hoiho]

So, this is the problem as i see it: once the oiled-cotton filter gets dirty enough that all the oil dries out, it’s possible for dusty air to make its way through the more porous filter media and into your engine, whereas a paper filter with it's much smaller voids would simply become blocked.

Am I missing something?

[viczena]

Do you want a blocked paper filter or a k&N which is regurlary moisted by the oil from the casevent?