K&N Air Filters.

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stchman

stchman

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Ok, I know that this topic may have been discussed ad nauseam, but I am acutually looking for some hard evidence, not just "my buddy said they let in too much dirt".

After a LOT of Googling, all I can find is forum banter that K&N air filters are junk, they are good, they are great, they will make your engine fail, etc.

I have used K&N air filters for years and never had an engine fail. I will however admit that I am wrong if there is some compelling evidence to back it up.

I have also noticed that no manufacturer will publish a spec on acceptable dirt level in an engine. I know that no air filter will remove 100% of all airborne particles, so there must be some acceptable level.

I have seen some folks post UOAs that show higher than normal levels of silicon in the oil, but what is considered too high and will damage engines. Then others post that PCV and other small vacuum leaks are more than likely responsible for higher than normal dirt getting into the engine.

K&N is a really big company with a great reputation, I would think that they would make quality products.

Thanks.
 
Fact is they filters are of good quality (construction wise) but they do let in more dirt and dust. A quality paper air filter will do a better job at filtering and will provide plenty of air to the engine.
 
Originally Posted By: gregk24
Fact is they filters are of good quality (construction wise) but they do let in more dirt and dust. A quality paper air filter will do a better job at filtering and will provide plenty of air to the engine.


No disrespect at all, but you saying it is fact does not make it fact unless backed up with testing and scientific data.
 
The filter test listed above says it all for me. I have yet to see where changing the drop in air filter has resulted in increased HP or increased mileage.
 
Last edited:
i too used K&N for years, and up till about 9 months ago had them in all my autos.. I performed my own "white glove test" I ran my k&m for 6 months, reoved the plumbing and ran my glove inside the throttle body intake.. yes there was very very fine dirt. same test with a napa air filter installed and almost nothing on the glove.. simple enuff, yep K&n lets in a bit more dirt.. I dont run them anymore for daily driving. However if im pulling a trailer or taking a over the road vacation i will throw my k&n back in.. ever so slightly more power and just a tick better mpg.. not much.. but a tad..
 
Originally Posted By: bobbobtar
Here are some tests done a few years ago.

http://www.dieselplace.com/forum/3-power...-they-work.html


Originally Posted By: Sunnyinhollister
The filter test listed above says it all for me. I have yet to see where changing the drop in air filter has resulted in increased HP or increased mileage.


To be fair, the test date on that was done in September of 2004.
 
Look up some UOA where people have used a K&N air filter, look down at the silicon, the higher that number, the more dirt and dust got in.
 
I use the K&N short ram intake im my CRV. I'm probably letting more dirt in than the OEM filter but I do feel a slight increase in power with "my seat of the pants dyno". I know that I won't go 3,000,000 miles like Irv Gordon did in his Volvo and I won't put 1,000,000 miles on my engine. Sure I'm probably allowing some rough particles into my combustion chamber which may scuff my cylinder walls a little or possibly cause a burnt valve or seat but as long as I can go 300,000 miles on my engine, I'm happy. I'm at 150,000 miles and don't burn any oil yet. I'm half way there with K&N.
 
I'll repeat what I just posted on the other thread. All you need do is compare efficiency specs. Before comparing, you need to know whether the spec quoted is based on an ISO 5011 test done with fine test dust or coarse. The numbers are better with any filter using coarse... and that's what K&N shows. They are ~98 percent on coarse. Same filter on fine... ~ 94-96%. Many of the better cellulose filters and some aftermarkets dry filters can do 98-99% on fine dust. 98% on coarse is generally OK in the larger scheme of things, especially if you live in a clean air environment, but since the air filter is the one door open to engine/oil contamination, better air filtration is... better.

The 2004 Spicer test is still valid in many ways, if nothing else to show the difference of the K&N on coarse dust vs fine. Most of the tests Spicer had done were on coarse but at the back, you will see a few done on fine. Note how far the K&N dropped on fine. K&N hasn't changed the basic design of their filters recently. Most are two layers of gauze. Some of the HD elements are three layers and their efficiency is better. If they used three layers on everything, we wouldn't be having these perpetual tiffs over efficiency. I agree that K&N is a great company with a great R&D department and you will be seeing some great things from them in the future... but oiled cotton gauze is an icon of the past.

There are also tests done by SWRI for AEM (which is now a part of K&N) that showed how much of a difference was between coarse and fine dust with a KN. They also did testing to show how much the K&N degraded when it was improperly cleaned. You can go from ~98% on coarse to around 75% if you aren't careful. When K&N bought AEM, those papers were removed but you could likely find them on the Wayback. I printed them out for reference.

As with other filters, run the K&Ns a long time and/or use a restriction gauge to indicate when it's time to change/clean. Efficiency dropped 1-2% on the K&N even when it was cleaned properly but efficiency on any fitler improves as it loads up-2-4%. That's important for a K&N because they will improve enough when dirty to nearly match the better cellulose filters but their design allows them to retain good airflow.

Randomhero: 3whp and 2wtq is well within the margin for error on every rear wheel dyno and moreso on ones that are infrequently calibrated or improperly operated. You can gain or lose that much by having hot transaxle oil or cool oil, and/or hot or cool engine oil. There are many other variables. Most times, there is an agenda and the best runs are cherry picked to show gains when they really should be 8-10 runs averaged. What was shown in the link was just two runs and no indication of averaging. Spent a lot of time in dyno rooms in the past 20 years.
 
Yes i realized that is within the Dyno error and too many variables to narrow it down to the air filter.

What are your thoughts on AEM dry flow filters? My Civic has a cheapo eBay intake on it and i wana replace the filter with something higher quality. Ive had good silicone numbers on my UOAs for my Accord (which has an AEM intake).
 
Originally Posted By: randomhero439
Yes i realized that is within the Dyno error and too many variables to narrow it down to the air filter.

What are your thoughts on AEM dry flow filters? My Civic has a cheapo eBay intake on it and i wana replace the filter with something higher quality. Ive had good silicone numbers on my UOAs for my Accord (which has an AEM intake).

I had a large cone filter on my supercharged L67 and I ran the Dry Flow for 50k miles and when I took it off the intake was clean to the touch.
Very good filter.

ROD
 
Originally Posted By: stchman
Are there any cases where using a K&N air filter was directly attributed to engine damage?


Probably but it's usually operator or installer error (improper cleaning, for example). As I said, K&N filtration is "adequate." If that's good enough for you... good enough!

Many filters have better efficiency, though. I got religion on this because if you want to do long OCIs, you have to eliminate as many contamination inputs as possible. The air filter is the primary route for contaminants in the oil so you want to eliminate as much of that as possible by having a high efficiency filter.

If you want to know how much difference various efficiencies make in the amount of dirt getting into your engine, check out this chart from an engineer at Parker Filtration.

Code:
For Every 10 Pounds of Dust Drawn Into the Air Filter Inlet:



EFFICIENCY OF FILTER DUST INTO ENGINE



99.95% 0.005 lbs.

99% 0.10 lbs.

98% 0.20 lbs.

95% 0.50 lbs.

90% 1.0 lbs.


Look at the difference between 98 and 99 percent, which is a typical difference between a premium cellulose and a K&N. Remember also that the ISO 5011 test is the final efficiency... that means at the END of the filter's life. At the beginning of service, they start at 2-3 (sometimes 4) percent less efficiency and that leads to the statistic, also from the engineer at Parker, that 90 percent of the contamination ingested by the engine over an air filter's life comes in the first 10 percent of use. The filters load pretty quickly and efficiency improves rapidly, so if you don't replace the filter too often, or clean it too often, you can run in that high efficiency realm a lot longer.
 
I wish somebody would collect all (or several) UOA's here that have a K&N as a filter and place them in one place for easy viewing and reference. We all have seen the effects but it would be nice to have a link to the info in one place.
 
wsar10: The only time a K&N would produce a wickedly bad UOA is if the vehicle was run in a very dusty environment, or had been badly mauled during cleaning. As I have said, they are "adequate" but not "superior" at the air cleaning game.

That said, we have seen some not-so-hot UOAs with K&Ns and some ok to good ones but they all are essentially useless for comparative purposes unless the vehicle was run first for a long period in it's normal environment with a "regular" filter and then over the same period and generally same operational cycle with the K&N. You might be able to glean something by comparing the K&Ns to the universal averages for the vehicle type and brand but that would still be a yardstick when a micrometer is needed.

The fact that the K&N, and most other oiled cotton gauze filters, are at the low end of the efficiency scale cannot be disputed. Whether it matters alot in all cases is another debate.. and largely a moot one. When operated in a relatively clean environment, with "normal" oil change intervals, there is little harm done, because filration is "adequate." Some of us need/want more than "adequate" so we avoid two ply K&Ns due the lower efficiency.

Hey, you have the same access to the UOAs as any here... you could be the guy to collect the UOAs into one place.
 
I am going to get a UOA here in about 2K miles. I will then put my factory air filter back in and do another UOA later down the road.
 
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