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      01-30-2008, 10:34 PM   #23
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Jim Conforti on K&N filters:

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:

It is incorrect. The difference between 99.2% and 98.1% (his results) is 1.1% not 224% as he states!!! 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



You decide...
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      01-30-2008, 11:01 PM   #24
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K&N filters are messy as hell
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      01-30-2008, 11:06 PM   #25
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Quote:
Originally Posted by SCCAForums.com View Post
The other thing is if you look closely at the first dyno graph... you can see the last two pulls (green and dark blue) the K&N pulls ahead of the stock filter after 6,000 Rpm... which is closer to the testing I found... and it made more torque.
Quote:
Originally Posted by Terry Burger
The first batch was with the JB2H, the second batch with the JB2HR. Each combination was run 2-3 times and the plot represents the best numbers of each. All runs were done with the same 2 minute cool down, on 96 octane.
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      01-30-2008, 11:52 PM   #26
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Quote:
Originally Posted by BzzzBom View Post
K&N filters are messy as hell
Huh?

No messier than any other aftermarket filter, which is to say is about as messy as it would be for you if you had to clean 1 wheel every 15,000 miles.

Trill, interesting find, good post.

What it really comes down to is the debate between stock OEM paper filters and aftermarket "oiled" cotton filters will rage on as long as the debate between whether Mobil 1 fully synthetic is better than Royal Purple.
Or whether Mother Wax is superior to Meguire's.
Or whether Chevron gas is better than Shell.

I personally saw a gain with the K&N filter.
I saw over 4 peak rwhp and 2 peak rwtq (but in some areas saw as much as 12-14 rwhp gains) and I did the first two runs on the stock filter and the third run with when my engine was at it's warmest with the K&N.

I know I kid about K&N, BMC, etc.
But they are both the same filter.
I've NEVER been a fan of foam filters and would never use them (ITG for our cars).

But I agree with K&N in the post Trill made.
They've been making filters for decades and everybody from onroad to offroad race teams use them.
Don't you think those race teams themselves have done some testing to see if filters like the K&N actually make more power?
And if they didn't stop the dirt from going into the engines, surely offroad race teams wouldn't use them for endurance races or rally races, or any other kind of dirt race where you suck in an awful lot of dirt.

The reality is, they seem to provide some power benefit, but surely if they were the greatest thing since sliced bread in the way of intake filters, manufacturers would use oiled cotton filters as OEM. I'm sure the reason they don't is because the benefit is small, and it's not worth the trade off of the cleaning maintainence for the average customer.
Cheaper and easier to just change a paper filter every 15K miles.
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      01-31-2008, 12:34 AM   #27
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I have read some BMW literature on their superior pleat design allowing tremendous surface area of effective filtering media. Its kind of hard to argue with the advantage of surface area. Surface area is your ally when it comes to air filters, radiators, intercoolers, heat sinks, pool filters, etc, etc. If it were superior to just use a simple one sheet membrane, everyone would do that. But the fact is, everyone goes through the expense of constructing these elements with more surface area for a good reason. As far as my 15 runs comparing my K&N vs Stock filter, I will make some more runs and then put the stock filter back in and see what happens. If there is any indication that the stock filter increases the overall HP, then I am leaving it in.
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      01-31-2008, 12:36 AM   #28
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Stock doesn't go VRRRRRROOOOOOOOOMMMMMM!

K&N sounds like VRRRRRRRRRROOOOOOOOOMMMM!
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      01-31-2008, 12:41 AM   #29
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Quote:
Originally Posted by NaTuReB0Y View Post
Stock doesn't go VRRRRRROOOOOOOOOMMMMMM!

K&N sounds like VRRRRRRRRRROOOOOOOOOMMMM!
Wow, I didn't notice any difference in sound with mine...but to me, whatever puts out more horsepower is gonna be my choice. I would take "quiet and powerful" over "loud and slow" any day.
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      01-31-2008, 09:40 AM   #30
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Wow, I didn't notice any difference in sound with mine...but to me, whatever puts out more horsepower is gonna be my choice. I would take "quiet and powerful" over "loud and slow" any day.
I'll go with that, but if something makes the same amount of power but goes vrooooom, I'll take that.
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      01-31-2008, 09:57 AM   #31
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Quote:
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I'll go with that, but if something makes the same amount of power but goes vrooooom, I'll take that.
Damn the Vrooooom...I'm after the power. I guess to some folks...vrooooom=power. I like my power minus the vrooooom now! Stealth!
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      01-31-2008, 02:10 PM   #32
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BTW, I got the gain from the k&N filter and I don't think it wasn't my car "adapting" to the dyno either.
As with my first two runs the car made essentially identical power, the 2nd run was actually a touch less than the first IIRC.
The gain came after switching in the K&N filter, it was also the run done with the most heat to the car. I did let the car sit for 7-8 minutes between the runs though. But still not enough to bring the temps back down to where it was after the frist and second run.

Next time I dyno I'll do the opposite and do the first two runs with the K&N and the third (and even do a 4th) with the stock air filter.
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      01-31-2008, 02:40 PM   #33
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Quote:
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BTW, I got the gain from the k&N filter and I don't think it wasn't my car "adapting" to the dyno either.
As with my first two runs the car made essentially identical power, the 2nd run was actually a touch less than the first IIRC.
The gain came after switching in the K&N filter, it was also the run done with the most heat to the car. I did let the car sit for 7-8 minutes between the runs though. But still not enough to bring the temps back down to where it was after the frist and second run.

Next time I dyno I'll do the opposite and do the first two runs with the K&N and the third (and even do a 4th) with the stock air filter.
I predict the power will be higher with the Stock filter this time around...
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      01-31-2008, 03:57 PM   #34
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I don't think there is a doubt that the OEM filter filters better than aftermarket.. but the question is.. how much air can it pass with the same amount of - pressure.
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      01-31-2008, 04:00 PM   #35
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If anyone want to do an independent test at home.. i think the easiest way is to get a bunch of dirt/sand or whatever u can find and make sure that they are about the same amount. Put the filter over it and get a vaccum <make sure it is 100% clean> and then just suck on the backside of the filter for a set amount of time and see what u catch in the vaccum. Yes, we won't see any % results but I think the naked eye can see a different between a small pile and a big pile.
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      01-31-2008, 07:09 PM   #36
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Quote:
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I predict the power will be higher with the Stock filter this time around...

Who knows.
Terry and I spoke this morning and discussed the stock vs OEM.
Though this dyno chart is a little misleading, Terry said, as the day went on, and he got several dynos on the car, he would let 2 minutes cool down time between runs.
He stated, with the car fully heated up at this point and swapping between stock and the K&N there was virtually zero change.
Meaning, once the car was on the dyno for a bit, fully adapted to it, and running at the same temps, it didn't matter which filter was in, he got the same results.

I do predict one thing is for sure, if I do it again, it will have different results than the first time around and give more people stuff to discuss.

As Terry and I both agreed, we don't see how it's possible for the K&N not to flow better, but as he stated, "it probably does to a degree" but the honest to God thing is, since there's really NO way to ever get the same results twice on a dyno, we'll never really know for sure.

I'm sure the OEM filter will do just fine for most.
If the K&N or BMC gives 2-3 hp at most, it's worth it to some.
All I know is, it's not enough of a difference to really worry our heads about anyway.
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      01-31-2008, 07:14 PM   #37
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Quote:
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If anyone want to do an independent test at home.. i think the easiest way is to get a bunch of dirt/sand or whatever u can find and make sure that they are about the same amount. Put the filter over it and get a vaccum <make sure it is 100% clean> and then just suck on the backside of the filter for a set amount of time and see what u catch in the vaccum. Yes, we won't see any % results but I think the naked eye can see a different between a small pile and a big pile.
Well I don't know if I'd use dirt.
I did a very similiar VERY ROUGH science project but instead of dirt I used a feather and my shop vac.

It seemed I needed to get about an inch closer to the feather with the stock filter than I did with the K&N before the vac. sucked the feather up to the filter.
The other test is those fan and ping-pong ball displays you see at autoparts stores.
They show more flow with a K&N too.

But again, it's car dependant and pretty minor when it comes down to it.
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      01-31-2008, 11:27 PM   #38
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E90AW335... I don't understand your quotes... it's still obvious... the K&N out flows the stock air filter from 6K on... on the same comparison of last two pulls?

"The other thing is if you look closely at the first dyno graph... you can see the last two pulls (green and dark blue) the K&N pulls ahead of the stock filter after 6,000 Rpm... which is closer to the testing I found... and it made more torque"

This is honestly stupid if you people don't think the K&N makes more Power...

Here are my dyno's... and I did them K&N IN FIRST... PAPER in 2nd... and both had the SAME mileage on each of them...

Honestly... if I had to race against any of ya... I hope you run the paper filter! :P

You can see my pulls are almost the same as Terry's... with the car making no gain unitl 5500... and then it's clear...

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      01-31-2008, 11:33 PM   #39
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If you look at the first graph with the stock box and stock filter it makes more power then the stock box and K&N filter. That is what I am saying....
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      02-01-2008, 12:24 AM   #40
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Thanks AW.... but look at the first graph... that pull is not right... whether it's pulling timing or what... it's obvious that pull is an anomoly... the two other pulls on there, are more typical to everyone elses comparison... where while it can be either plus or minus 1 or 2... it's never that drastic of difference... especially up high... where it showed again in his own test... that the K&N flowed more. Just as my tests showed, and others.

Peace,
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      02-01-2008, 03:14 AM   #41
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I used to use my high power shop vac to see the restriction difference of my aftermarket catalytic vs stock on my GN. I would hold the vacuum hose to the pipe sealing it with my hands and feeling the strength of the pull. I could definitely feel the difference. I'm sure you could hook a vacuum gauge up to the hose and with an adaptor to the air box, measure the restriction differences.
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      02-01-2008, 11:04 AM   #42
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Quote:
Originally Posted by SCCAForums.com View Post
Thanks AW.... but look at the first graph... that pull is not right... whether it's pulling timing or what... it's obvious that pull is an anomoly... the two other pulls on there, are more typical to everyone elses comparison... where while it can be either plus or minus 1 or 2... it's never that drastic of difference... especially up high... where it showed again in his own test... that the K&N flowed more. Just as my tests showed, and others.

Peace,
Dave
Agree to disagree....
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      02-01-2008, 11:26 AM   #43
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fwiw... On a sock engine the OEM paper filter does not seem to be a limiting factor. Kick up the boost and put on other engine mods and now airflow starts to become an issue. Jim's analysis seems spot on to me: if keeping grit out of your engine is a priority, use stock filter. If increased flow is priority, consider the aftermarket ones. If you are going to compare power output, use a new OEM filter, not your old clogged one.
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