Interesting Air filter review

[Jeff N.]

http://home.stny.rr.com/jbplock/ISO5011/SPICER.htm

[Sweetwater]

http://home.stny.rr.com/jbplock/ISO5011/SPICER.htm

I vote for a sticky here.....

Happy New Year.

[bigtisas]

In a nutshell, we don't need K&N.

[nirvana19]

Is K&N really THAT bad? Those figures say yes and it seems unbiased so I guess so. Always though K&N was a decent brand though.. glad I stuck to regular

[philbyil]

K&N's may be fine for an application that requires minimum filtering/restriction but, especially in the case of BMW's, stock filters have been proven to be the best for OUR applications. A similar test was done on a couple of motorcycles with virtually the same results and there was also a study published (trying to find it!) showing stock vs K&N filters on a BMW Boxer motor and the stock filter was actually better all around.

I have only ever used BMW or OEM BMW filters in both the car and my bike.

[Jon K]

I wonder how the newer AEM and ITG filters compare

[attack eagle]

more airflow = less filtration.
CAVEAT:
unless you are significantly increasing the size of the air filter without changing filter element construction... not really feasible in most cars.

[Anton CH.]

I remember reading a not-so-scientific test done on air filters. K&N basically came in last. Apex'i came first in terms of filtering power. It's the one I am running right now, it uses dry technology so you never need to oil it.

[NovceGuru]

http://www.bimmer.info/forum/showthread.php?t=19852

:P

[AngryPopTart]

I know rodders who have been running engines over 200k using either no filter at all (just scoops) or a metal screen (at the bottom of the scoop) and the engines are not getting tired or anything. And they always have their foot in it. Now, as far as it making the oil dirty faster, okay, but if you don't give oil a chance to go bad, it won't. These guys change every 2k (me too), at the very least so it really doesn't seem to matter.

I see alot of tests that prove one filter filters better than the next, flows better than the next, etc. I haven't seen one that proves using one filter as opposed to another, or no filter for that matter, causes premature engine failure in comparison to actually using one. Unless you're a fool who let's the oil get completely contaminated and useless, I don't see what the problem is.

However, I do see how this could be a problem to an extent on many cars since it would probably cause, say, a MAF to get dirty faster. Other than that...? What say you?

[attack eagle]

That dirty doesn't get to your oil... until it has been in the cylinder scratching up the walls.

[leicesterboy15]

Is the AC Delco standard fitment? I have a K&N in mine and I haven't noticed any difference really, good or bad, with the performance or sound. My MAF is still fine and I've been running it for about 8k now.

But surely it stands to reason that a more free flowing filter is going to let more dirt in but isn't it striking a balance between a 'safe' amount of dirt and restricting performance? Do these tests depict a true driving environment? How likely is it that something that gets through the filter could get the chance to scratch the cylinder walls before it is burnt up in the combustion? How weak are the cylinder walls if they can withstand combustion?

I guess if it's not making any difference I shouldn't take the risk and all the above are probably not likely but theres always a chance no matter how small.

I am not pretending to know these things when I don't, in fact I don't even understand half the technical details in the article, I'm just looking at it from a real life point of view and playing devils advocate - what do you guys think?

[Morgenster]

What about the filter's performance in the face of frozen condensation? I hear paper filters can turn into serious blockages during harsh winters.

[spyrot1]

Just playing the Devil's advocate (I also use K&N filters on all my cars and I have never had a problem)...

Taken from www.bmwe34.net:

K&N Response:

It is incorrect. The difference between 99.2% and 98.1% (his results) is 1.1% not 224% as he states!!! (bmwE34.net: who didn't go to school, Jim was measuring the amount of dust that goes inside the engine). Furthermore, does he realize that 96% meets OEM standards? K&N has been around for over 30 years and we sell over 2,000,000 units a year. If there were any sort of problem, one would think we would know by now and so would everyone else. One Internet "expert's" opinion is not reason for concern and should be taken loosely at best.

That information is 100% untrue. Don't believe all you read on the Net. Most is opinions not based on any sort of factual evidence. Our filters are tested by an outside, independent laboratory. They have been proven to stop at least 99% of particles on a SAE dust test. This test uses particles as low as the 0 - 5 micron range and goes up to 20 microns.
For comparison, a paper filter also stops 99% on the same test and the OEM minimum standard is 96%. Foam is generally the worst media with a typical efficiency rating of 75 - 85%. To get higher ratings, the foam must be more dense and therefore way more restrictive. The "tack" characteristic of a K&N allows for increase filtration without loss of flow as well. The testing procedure used is SAE J-726 using ISO Test Dust.
This test is the standard of the air filter industry. The test procedure consists of flowing air through the filter at a constant rate (airflow rate is determined by the application) while feeding test dust into the air stream at a rate of 1 gram per cubic meter of air.
As the filter loads with dust the pressure drop across the
filter is increased to maintain the prescribed airflow rate. The test is continued until the pressure drop increases 10" H2O above the initial restriction of the clean element (in this case .78" to 10.78" H2O). At this point the test is terminated. The dirty filter element is then weighed. This weight is compared to the clean element weight to determine the total Dust
Capacity. The amount of dust retained by the filter is divided by the total amount of dust fed during the test to determine the Cumulative Efficiency.

The K&N filter achieved the following results:
- Dust Capacity: 305grams
- K&N Cumulative Efficiency: 99.05 %

Holding the filter to the light is useless, pin holes are normal.
That is what makes a K&N filter. There are actually hundreds of microscopic fibers that cross these holes and when treated with oil, capture and hold the very fine particles. On the same hand, they allow the filter to flow more air than paper or foam. The filter is 4 ply cotton gauze unlike some competitors synthetic material filters. The synthetics do not
have the very small fibers that natural cotton does. Also, the oil can be pulled off of a foam filter contaminating electronic sensors. It will absorb into cotton and stay in the media. In fact, Honda and Toyota only recommend K&N filters when using aftermarket high flow filters as K&N is the only brand of filter the oil does NOT come off of. They will not cover a failed sensor if foam filters were used.
We got started over 30 years ago making filters for motorcycles and off road racers. The filters did so well that these guys wanted them for their cars and trucks. We started making filters for these applications and here we are today. If they did not work, we would not still be here and growing every year.
We now make filters for Chrysler/Mopar, Ford Motorsports, Edelbrock, Rotax Engines, and Harley Davidson. We come as original equipment on the 2000 Ford Mustang Cobra-R. We even made filters for the Apache helicopters used in Desert Storm because of maintenance problems with the original paper design. If they work in these conditions they will work for you.

Rick from knfilters.com (Information emailed by Martin)

let the flaming begin!

[attack eagle]

Is the AC Delco standard fitment? I have a K&N in mine and I haven't noticed any difference really, good or bad, with the performance or sound. My MAF is still fine and I've been running it for about 8k now.

But surely it stands to reason that a more free flowing filter is going to let more dirt in but isn't it striking a balance between a 'safe' amount of dirt and restricting performance? Do these tests depict a true driving environment? How likely is it that something that gets through the filter could get the chance to scratch the cylinder walls before it is burnt up in the combustion? How weak are the cylinder walls if they can withstand combustion?

I guess if it's not making any difference I shouldn't take the risk and all the above are probably not likely but theres always a chance no matter how small.


you aren't going to burn up silicon... aka sand. primary component of dust around here. maybe pollen but not sand... and none of it is good for your engine.

the point is for a modest 2 to 0 hp gain you are letting more dirt into the engine... and K&N agrees that it is 224% more dirt. ;) cause they are geniuses at marketing, not numbers.
the safe amount of dirt is 0.000000000 percent.


i like his retort that "if there was a problem, people would know about it..." problem is they do. people don't see any gains after driving a week or two on a k&N only when they are freshly cleaned, you get oil on your maf with them because it is impossible to get "exactly" the right amount of oil that provides maximum protection without bleeding, and finally that most of the GAINS in economy are a result of increased audible intake noise resulting in a reduction in throttle application by the unacclimated driver.


btw Ihad an FIPK on my last car becasue it was the best option on a DSM. the airbox location means the post ic piping is as flat as a vaccuum cleaner nozzle, so you have to dump the box to get bettor normal piping in.

K&N better than foam, but paper better than k&N

[AngryPopTart]

That dirty doesn't get to your oil... until it has been in the cylinder scratching up the walls.

That explains why I don't see any difference. I don't think the air filter will ever be a bottle-neck in my 525i so it probably doesn't matter either way. Except that you can change the sound the car makes by playing with the air-box, right?