[Biturbos4] Re: K&N filters bad?
b5quattro at shaw.ca
Thu Mar 11 19:11:19 EST 2004
I've read this one from a few years ago, thanks for refreshing my memory!
----- Original Message -----
From: Ti Kan <ti at amb.org>
Date: Thursday, March 11, 2004 11:11 am
Subject: [Biturbos4] Re: K&N filters bad?
> Yet another interesting read from the main audifans quattro list
> on this subject.
> 2003 A4 1.8T multitronic
> 2001 S4 biturbo 6-sp
> 1984 5000S turbo
> 1980 4000 2.0 5-sp
> R 1 3 5 Ti Kan
> |_|_|_| http://www.amb.org/ti
> | | | Vorsprung durch Technik
> 2 4 6
> Forwarded message:
> > From: David <duandcc_forums at cox.net>
> > Date: Thu, 11 Mar 2004 9:27:12 -0500
> > Subject: Re: K&N filters bad?
> > 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
> > Comparing 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
> > >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
> > 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.
> > Dave
> > 87.5 CGT
> > SE Virginia
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