Interesting read RE: K&N Filters...
 

From a Bimmer site...:D Food for thought... Let the games begin...

Jim Conforti (AKA the Land Shark) did some testing:
This was a scientific test, not one done by filter manufacturer X to show that their filters are better than manufacturer Y. The test results are pretty irrefutable as the test lab tests and designs filters where "screw ups" are absolutely NOT allowable (I can't say any more for security. Think "Glow in the Dark").

A scientific test was done on TEST filters where air was loaded with ACCTD (some standardized "test dust" called AC Coarse Test Dust) and sucked through the TEST filter then through an analysis membrane. From the Quantity of dust injected and the amount that gets through the TEST filter and is then captured on the analysis membrane we can calculate the efficiency of the TEST filter in Question.

BMW Stock Filter, Eff. Area of Media: 8.4 sq ft.
K&N Replacement, Eff. Area of Media: 1.6 sq ft.

The filters are the SAME size. They both fit in the STOCK BMW M3 airbox. The difference is that the STOCK filter has 65 pleats 1.5" deep and the K&N only 29 pleats each 0.75" deep.
Now, remember this ratio: " 5.25:1". It's the ratio of the AREA of STOCK to K&N. It's very important and will come into play later.

The STOCK filter efficiency started at 93.4% at 0 loading and increased to 99.2% efficiency as the loading increased to a max tested of 38.8 gm/sq ft of dust.


The K&N filter efficiency started at 85.2% at 0 loading and increased to 98.1% at the max tested loading of 41.38 gm/sq ft.

Now, I hear you. "Jim, that's only a FEW PERCENT". But is it?

Let's look. If we had 100 grams of dust on a new BMW filter we would let through a total of 6.6 grams of dust in. If we used the new K&N filter we get 14.8 grams of dust. That's 224% (TWO HUNDRED TWENTY FOUR PERCENT!!) more dust ingested initially, stock vs. "free flow" and this ratio is pretty much held. Somewhere between 200-300% more dirt gets "ingested" anywhere across loading equivalence. The more INTERESTING thing is when you look at what happens to the DP or Differential Pressure at a constant airflow as you dirty both filters equally with time.

The test used a rate of 75gr of dust per 20 min. Here's where the AREA difference comes MAJORLY into play. See, even though the BMW filter flows a bit less at the SAME loading, it also LOADS UP 5.25 times SLOWER due to it's LARGER effective area. So what happens is that the K&N initially flows better, but as the dirt continues coming in, the K&N eventually flows WORSE while still letting MORE dirt in.

Now, does any of this additional dirt cause problems? I dunno. I suppose we could have a few people do some independent oil analyses on different motors using both K&Ns and Stock filters. Get enough of them, and you'd have a good statistical basis. For me though, it's simple: More DIRT = BAD.

The additional short-term airflow might make sense on a track car. IMHO, it doesn't for the street.

-- Jim Conforti

K&N Response:

This 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 opinions are 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

Another interesting note seen in the March 2004 Panorama pg. 58 is the following statement "A BNC or K&N filter in the car can cause a problem with the oil on the filter passing through and ending up on the [MAF] sensor; causing a bad reading.

The above is refering to a Boxster, but still interesting that they claim oil in the filter may be going into the induction system.

I tend to think the best air filter is an often-changed OEM paper version.

Inexpensive insurance as an ineffective air filter can destroy an engine.

Its pretty well known, I always thought, that K&N filters both let in more dirt and the oil tends to negatively impact MAF sensors on cars so equipped.

Its a big problem on Audi S4's, I know. Everyone I know who had K&N's on their car kept having to replace one MAF after another until they went back to a stock filter.

Every manufacturer has a claim. I don't think the " ..we are still making them" argumant is very sound since Ford made alot of Pintos and Mustangs with fauty fuel tanks. Since there are no recalls for bad after market parts we are left to wonder if the filters work. I have to believe the ads bacause I have no other source of information.

I recently saw an ad for an Amsoil foam fiter. They claim that it filters better and flows very good (twice as good as stock), they did the same dust tests against a K&N filter and a stock filter. Their filter was better at removing dust and flowing air.

http://amsoil.com/products/ts.html

the problem is that a bad filter will not cause a motor to fail right away. we cant go, "damn you, k&n, look what your crappy filter caused!" it is pretty easy to get a bunch of kids all caught up with that on the counter display with the ball that floats on a pocket of air. the ball always floats higher with the k&n. just that every old timer original motor car with hundreds of thousands of miles always have the stock filter. for years i had a K&N on my pickup. everytime i clean the filter, i always take a damp cloth to wipe the airbox out. it was an epiphany, when i realized "WHY!". k&n suck.

Pipercross all the way

Ohh yes!

Wolfram wire in MAF that is used to measure air mass flow is heated to 700 degrees Celsius every time you shut off the car, to burn eventual residue. Problem is, when it gets coated with oil and then heated to 700 deg. the oil will coke and eventually either degrade and snap the wire or isolate it from surounding air.

A few comments from a science friend of mine:

1. If the K&N efficiency was 85.2, and the stock 93.4 at zero load, they both failed, since as the K&N response points out, the acceptable level is 96%.

2. The data doesn't support Jim's assertion that the stock filter holds more dust because of the plethora, myriad, or even multiplicity of pleats. The K&N filter conked out at 41.38g/sqft, the stock only held 38.8. Doing some math here, the efficiency per square foot for the K&N is 25.8625, while the stock filter is 4.619047(repeating decimal).

The conclusion I draw here is that the K&N keeps filtering when the air is 106% as dirty as with the stock filter, and does so with less than one fifth the material.

Okay, it's time for a real world test.

Let's run the left side of a 911 engine with a paper filter, and the right side with a K&N.

Now lets go run out test car like a banshee through the Mojave desert, through gravel forest service roads in the Colorado mountains, and enter in in the OTC. After a few hundred thousand miles, we'll tear down the engine, and inspect for wear.

My car is Motronic, and only uses one filter. Anybody with Webers want to donate your car?

Since running with no filter at all on a stock 3.2 doesn't make any more power, why would anyone bother with a K&N in this application?
-Chris

I would love to have a real test. The test mentioned by Amsoil seems to be objective but it is hard to believe companies ads. This would be a great topic for Panorama or Sports Car or GRM or....

I think the only advantage of a reuseable filter is that it is...reuseable. No thrown filters. No land fill junk.

It also seems that the longer between cleanings the better because filtering drops when clean.

I have an almost new K&N filter for 3.2, with cleaning kit and almost full bottle of oil....for sale.

PM me if you are interested. Make me an offer.

The PO purchased it. I removed it immediately upon purchasing the car from him.

sonic

It's the same reason someone would buy an off the shelf chip or swear on their momma's life that gas from Station A is better than Station B, after you had just witnessed the same tanker deliver gas to both stations.

K&N has done what many others do, exaggerate performance claims and try to sell their products based on the "coolness" factor.

The "coolness" factor evolves the older you get, thank god...

Run faster, Jump higher!!

Originally posted by ChrisBennet
"Since running with no filter at all on a stock 3.2 doesn't make any more power, why would anyone bother with a K&N in this application?
-Chris"

If you take the muffler off and doesn't make any more power why bother with a performance muffler? :D Just playin...

Apples and oranges. They weren't the same test. They didn't use the same dust. You can't compare the filter efficiency results against the SAE standard.

Neither filter 'conked out' in the first test. The poster does not give the criteria used for determining when the test ended. In fact the difference betweer 38.8 and 41.38g/sq ft is only about 6%. It could be that this test procedure is to stop in the neighborhood of 40g/sq ft. We'll never know.

However if you look carefully at the units he is saying that at 41.38grams per square foot of filter media the K&N filter was working at 98.1%. This would mean that after being loaded with 66.2 grams of dust (1.6sqft * 41.38g/sqft) it was passing 0.07grams per minute (70g/20min * 98.1%)

The Stock filter was tested until it was loaded with 38.8 grams/sq ft of filter media. When loaded with 325.9 grams of dust it was functioning at 99.2%. So it was passing 0.028grams per minute.

So the stock filter was took 4.5 times as long to get loaded to roughly the same level on a per area of filter basis and at the end was passing about 40% of the dust that the K&N filter was passing.


This conclusion is based on the idea that the filters stopped filtering by the end of the test. This is not the case. Both were filtering still at the stated percentage. I believe that you have also mistaken the 38.8gr/sqft and 41.38g/sqft as measurements of the amount of dust in the air, but that would be g/cubic feet. They are talking about loading on the filter surface.

What I don't understand is how in the first test the efficiency was measured at the different loading levels. Jim described the method as using a secondary filter to capture the dust that passed the test filter, then somehow the amount of dust on the secondary filter was weighed or measured. This method would only produce and average efficiency for the whole test.

The K&N representative does not present his test results in context with test results from stock filters. Also nothing here addresses how a K&N filter performs at varying times after the oil has been applied. Is it as effective after one month of use? One year?

I don't believe that anyone is claiming that under the SAE test conditions that a K&N filter fails to meet the 96% criteria.

Mike Benefield, PE

I can't understand why anyone would run a K&N filter in a stock airbox, but I can totally understand why you'd want to be rid of the stock airbox. A cone filter gives you better maintainence access, and is easy to remove to get out of the way, plus with a cheap piece of pvc elbow you can get it out under the grill where there is cooler air. Same reason you'd backdate your heat, cleans up the engine compartment.

I could really care less about all of these dust comparison tests, as what they all ignore is whether the "extra" dust passed thru the oiled filter is actually harmful, as opposed to assuming that its harmful. I submit that in the real world, regular runs to 6k probably have more affect on ultimate engine life than which filter is used.

There are two reasons I posted this... one, simply to see the response...two... to see the response.

What interests me in this whole issue are how the "opinions" of various sources are ascertained. Most are spouting internet rhetoric, or passing on false info riding the band wagon. Both on the pro side AND con side. Personally the subject is interesting, as it GLARINGLY shows the overall distrust of corporate claims. While some of these are indeed true, I think most corps get the bad rap when it comes to "claims" of product usefullness. The reality of ANY test that is based on stats is they can be "tweeked" in whatever way to make a point. I think it's somewhat sad that most people (to include myself) tend to fall into the "believe the negative" catagory and totally disregard the positive, simply because it's a large corp "making money".

We will never know whether or not the K&N is the garbage filter, or if paper is the engine savior... because as the previous post stated, the reality is that MOST engines get far more abuse from lack of care, than any filter could cause.

BTW, I've had a K&N type of filter (MSDS cone system) on my car for 5 years. Never an MAF problem, nor has there ever been any sign of dirt or oil residue in the intake. My guess is, like most problems that occur in the auto world, that issues arise from USER related errors or incompetence. My opinion of the filter is, I've never had a problem, and my mechanics, racers etc. that I know, don't have any problems with them either.

Fun thread!!!

re opinions, see my post today on the msd thread.

But "reality of ANY test that is based on stats is they can be "tweeked" in whatever way to make a point." is not true. Many valid statistical analyses are too clear to "tweak" -- not all. Your stmt is too extreme.

re user error -- Good product design compensates for user error. There is no way a paper filter will oil up a MAF wire. I'm not claiming paper is better mind you.

Fair enough on both counts... I just think the internet, for all of it's good has some pitfalls of "misinformation" that tend to be looked upon as the ABSOLUTE truth (both sides mind you) without further analysis. Not always, but often.

This K&N thread was not meant to prove anything, just to see the reaction to "stats" from both sides. And, as I thought, most of the K&N info was either ignored or called as incorrect, or misinformation. There are always two sides to every issue. Otherwise our spirited chip debates would never occur!!!

http://www.pelicanparts.com/support/smileys/wat6.gif

"I just think the internet, for all of it's good has some pitfalls of "misinformation" that tend to be looked upon as the ABSOLUTE truth (both sides mind you) without further analysis. Not always, but often."

Wow - now that is an understatement! The internet is the least reliable information source I know. Maybe word of mouth would be less relaible for most people, but most of the mouths I interact with are prudent and knowledgeable.

I propose ghettoizing all chip posts to a separate forum....

Has Consumer Report or other independent source done a test on filters? It is very hard to be objective when your magizine advertises a product. Companies are trying to promote their product so they are notorious for false advertising. I think there is a missing conclusion.

Why doesn't the PCA create a test site for various products using objective testing and verifiable results? We could pay a small fee for information to cover expenses.

We have to tell PCA that. I will if you will. Only a large no. of requests will motivate them.

I have always thought that the "club" concepts was to promote common goals and improve knowlege. I have not had much benefit from some of the organizations I have paid to join but many of the "Car Clubs" seem to have a real curiosity about improving their cars. I will write a letter and tell you the reply.

Randy,

I sent this letter to the Tech Dept of PCA to see if they have any possible answers. While I was there I did read an answer about using K&N Filters with a new intake which they seemed to think would add 5HP. They also said that no filter made noe change in HP. ???

It would be nice to have some objective answers. My letter below.

I and other Porsche drivers are always interested in improving/maintaining the performance of their Porsches. The problem is what do we believe?

Manufactures always show their product in the best light but rumors persist that certain changes are bad (some filters allow more dust/dirt and cause damage). I am speaking specificlly about the K&N Filter but there are many others. Some owners are so fearfull they will only use factory parts.

I have read many articles about synthetic oil, oil filters and air filters that significantly reduce engine wear and improve performance. I have owned reuseable oil filters that have significantly extended oil use (40-50,000 miles) with no significant wear. I would like to be able to take advantage of advances that improve performance and durability without sacrificing money or time to find the best answers.

The PCA could create a system for basic engine adjustments (oil, gas and air filters) that are and can improve or maintain engine performance. PCA could test a variety of products using verifiable results and make the information available to members for a small fee (to cover costs). I am sure this would help settle disagreements about what really works without any bias. Has this idea been suggested and is it practical?

Just a question. Has anyone here lost a motor, know anyone who lost a motor becuase of a K&N Filter? I dont, but I dont think they are better than stock either. But It sure seems like there should be a ton of busted up cars out there becuase of them. I would imagine K&N will be going bankrupt soon due to all of the law suits from peoples whos motors failed prematurely.

Sorry to sound sarcastic but I hear a ton of data on how bad they are and no data on the faliures that would surely be cuased if in fact this data is true and the assumptions are correct.

I am confident I am going to get my backside handed to me on this topic but I just want to see the data on the ramifactions of the extra mega tons of particlate that is being consumed by so many motors across the world. School me.

Thx DG624 - I will send in something similar. I hope other s will push for this also.

BTW, whether a different air filter will add hp or not depends on whether the stock filter is the "weak pt." the rstriction in the intake/exhaust system. Bruce A's column indicates that it is on some years and is not on others. Same concept as growing a big heart in your body to win a foot race -- no help unless the lungs are also bigger, and the legs longer, muscles stronger, etc...

Won't happen.
 

and right now I have K&N filters in my SC and my 740iL.

I can't see PCA ever conducting independent tests as long as they obtain advertising revenue from both K&N and Porsche NA. Why upset either 'customer' when they both advertise in PANO? The only way it would ever happen is if enough owners paid for test results to cover the loss in revenue when the "loser of the test" stopped advertising (and they would). I'm no marketing expert, but I would wager that beyond the subject being a talking point, not enough of us would buy the test results to cover the first month's loss in advertising. Face it, we'd get one copy of the test and pass it around. :D

IF enough ask it will happen -- we can also try Exl. mag.

I hope you're right and I'm totally wrong. I'm getting more cynical with age but I'm willing to try. It would be good if all the mail went to the same person/department. A totally independent, scientific test is the only way to put this to rest once and for all.

The K&N cone pulls more air than the BMC cone with the open end on it. Or at least my car is measureably quicker with the K&N. I ran three more G-Tech tonight with the BMC and it is a good .1 to .2 slower 0 - 60 than the K&N. I had hoped that the new BMC would give me a boost. Pretty dissapointed in it.

D. Hanson, if you tell anyone on this board that your K&N makes your car faster they will tar and feather you. Be carfull, its a lonley place on the K&N side of things.

These filters have been tested up the wazoo and in practice they make very little difference. I few HP loss here and maybe a couple of HP more there. They just aren't going to make much of a difference on a well designed motor. I remember someone dynoed a 3.2 with no filter at all and got a 3hp loss. Is anyone going to feel 3hp? It wouldn't surprise me if a motor made 3 more horsepower in the morning than it does at noon due to temperature differences.
The 3.2 and 964 3.6 run open loop at wide open throttle (ignoring the air flow meter) so no more fuel is added even if more air comes in. If the motor was running too rich before, maybe the added air will lean out the mixture and net a few HP. That's what a good chip is for though.
-Chris

My 914/6 came to me with K&N filters. After 1.5 years, the engine had tremedous blow-by.

I had the engine torn down and rebuilt. The Bottom end was perfect. The rings were done. The rebuilder asked me what air filter I was running: K&N.

I bought a stock airbox and stock filters.

Remember:

If you are running fuel injection with a MAP or air flow sensor, the filter will only hurt you at WOT. The throttle at anything other than wide open causes much more pressure drop than the filter. The engine doesn't care where the pressure drop comes from.

Carbs and MFI are a different story...

I know. That is the risk you run. Perhaps it would make a difference beuase I am not comparing a stock air filter. There is an absolute difference in power though between the BMC and K&N design. The K&N has a large air in flow surface.

Not only are the G-Tech times slow, My car does not catch second and third gear nearly as well when I am getting it. It is pretty night and day when I do the swap.

I put my stereo gear back in last night 120 pounds, reset the DMEnand reinstalled the K&N. The K7N was afster with the extra 120 pound 0 - 60s done only 30 minutes later. So far I have performed six 6 with no stereo equipment with the BMC and ll six runs were amrkedly slower on the G-Tech than the 6 runs with the K&N cone filter runs which included three heavy runs with all of my stereo gear installed.

Take it for what it is worth, but my experience is that the K&N gave better breathing and accelleration than the BMC fancy cone filter.

Caveat:

One problem that I may have encountered is that the end of the filter may have been somewhat covered up by the rear hinge of the deck lid. I don't have one of those pipes that redirect the filter out into the open. The end of the filter came very close to this hinge and when close, it looks like the hinge may really impeded air flow at the end.

I received this reply from PCA about testing air filters:

I think this is a great idea, however so many independent publications exist that do their own testing. For example consumer reports does various testing on all sorts of things. The man hours and time to do these types of test is almost not practical unless that is the business you are in. I have done several equipment test not through the PCA and I can assure you that the time to do it right and in a complete manner is extremely time and money consuming. It is really not the position of the
PCA to test and endorse or not endorse product. Our function as a Tech committee is to help you as the end user receive accurate information in regards to your specific model. In many cases the best choice of product is the factory version or the original OEM. We know that Porsche stands behind their product and it has been tested and tested time again.


Stephen Kaspar - PCA WebSite - 4/4/2004

I guess we should start looking through "Consumer Report" to find an unbiased source.

It is assumed it was the K&N, what was the previous history of the motor? Did you get it from a fresh rebuild with K&N filters or was there mileage on the motor?

Sorry, it could 'loosly' be assumed the K&N was the problem, but there could have been some previous issue/issues unknown to you. It is hardly emperical to say the K&N was completely at fault.

Apperently Jim Conforti has no problem using ITG filters. I thought those were as satanic as K&N and BMC?


https://secure3.nexternal.com/shared/StoreFront/default.asp?CS=bimmerworl&BusType=BtoC&Count1=9986 23073&Count2=915763497

Sigh...
This thread (and almost all other K&N threads) make an eronious assumption that ALL dirt particles that enter an engine will create wear and damage.
I suggest there is a point where particles uder a certain size will not cause measurable wear. Same with an oil filter. There is technology available to filter oil down to sub-one micron size but no one runs them. Why? because it would be a waste of time!
An engine with a 5 micron oil filter will last just as long as an engine with a 1 micron oil filter.
it would be easy to design and sell an air filter that will trap 99.99999% of all measurable particles and still provide good flow using commonly available technology based on latest generation HEPA. No one has done it because I don't believe it is necessary or of any benefit. The cost would drastically outweigh any perceived benefit, real or not (and I say not).

IMHO, a K&N filter will not provide any notceable increase in power on a 3 liter CIS equipped engine. I have tried it and the seat of my pants could not tell a difference.
I also suggest that the amount and small particle size that gets past a well prepped K&N filter and also an OEM filter is too small to worry about.
I believe If an engine is equipped with a K&N filter and the filter is maintained and installed correctly, that engine will last just as long as the same engine with stock filters.

For what it's worth, I'd like to throw out a little background on the beginnings of K&N, as I am good friends with one of the founders. The name of the company was derived from their first names, Kenny and Norm. At the time, they did a bit of racing in the dirt for fun and invented this new filter to keep the dirt clods out of their carb intakes. Others took notice of what they had done and they began making them for off-road racers and sprint cars, and the like. The original intent was simply to keep an engine alive for the duration of whatever race it was in.

Years pass and my friend gets out of the business, which takes off big time, supplying motorcycle racers and others with air filters. Then came the street bike aftermarket filters and carb jetting kits, followed by the realization that the car aftermarket was lucrative too.

It's certainly a much different company than what it started out to be.

Gotta go to work now,
JR