K&N airfilter

Peter Schulz peschulz at cisco.com
Thu Jan 9 12:45:39 EST 2003

At 09:10 AM 1/9/2003 -0800, joe smith wrote:
>Other than not ever having to buy another air filter
>is it worth putting a K&N air filter in my 20v? Iv'e
>read that it will add 5 to 10% increase in HP - I
>don't buy that. What are your thoughts - is it worth
>doing or not?
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More airflow means more dust into the engine - since the particles aren't being trapped.
You will continually run the risk of ruining your MAF from any oil that travels to the wire from the filter media.

You will still need to clean and reoil the filter periodically - so you might as well stay with paper....

Most of us do...


read the following from my archives...then you decide...

>From: Paul Royal <paulr at bavauto.com>
>To: "Audi 20V" <audi20v at rennlist.org>
>Subject: [audi20v] FWIW ON FILTERS
>Date: Tue, 6 Feb 2001 16:33:26 -0500
>X-Mailer: Internet Mail Service (5.5.2448.0)
>List-Unsubscribe: <mailto:leave-audi20v-39500G at rennlist.org>
>Reply-To: Paul Royal <paulr at bavauto.com>
>Are "Performance" Air Filters a Good Idea?
>The following information was taken from a posting by Jim Conforti (AKA
>the Land Shark).  Jim is a well known tuner in BMW circles.  His web site is
>the Bonneville Motor Werks.  The testing was done on a BMW air filter but
>the concepts should apply to all manufacturers.

>omparing Stock to Performance Air Filters
>First, a "prologue".  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").
>OK, with that in mind, onward.
>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 thru the
>TEST filter and is then captured on the analysis membrane we can calculate
>the efficiency of the TEST filter in Question.
>First, the filters:
>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 thru a total of 6.6 grams of dust in.  If we used the new K&N filter we
>get 14.8 grams of dust.  Thats 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

Peter Schulz
1990 CQ
1991 200 20v TQW indigo mica
1991 200 20v TQW titanium grey
Chelmsford, MA USA
peschulz at cisco.com

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