[s-cars] Re: MAF foul up

Tue Mar 4 09:31:19 EST 2003

I ruined my MAF with a K&N in my 200q20v so  I'd avoid them like the
plague.
But, I have to admit, they have a great marketing department, they
suckered me!

Chris (s-carless and carless now)

On Mon, 3 Mar 2003, Fred Munro wrote:

> Right you are, Tom. I've seen two listers post of problems with K&N - one
> found the inside of his intake hoses coated with dust and the other found
> the leading edges of the cold side turbo blades eroded from "foreign
> particles". Both switched back to paper filters.
>
> I have attached a post comparing K&N to stock BMW paper filter performance
> for the edification of the S-car fraternity.
>
> Fred Munro
> '94 S4
>
> ATTACHMENT:
>
> Here's a post that came up on the 924/944 list a while ago on the same
> topic, that I have posted to this list before.  Solved it for me.
> Paper filters are awfully cheap.  I can replace them for a heck of a lot
> of times for the cost of a K&N anyhow.  Let's see $50 for a K&N, or
> under $10 for a paper filter.   Assuming a 20k change interval, that's
> 100k miles worth of driving before I've even reached the cost of the
> K&N, and that is before I buy the oil, so the cost savings isn't even a
> point for me.
>
> Here's the post:
> It was done on a WMB, but should be similar of course.
>
> Enjoy!
>
> Greg Roa
> Cincinnati, OH
> 86' 4kcsq
> 93' 90 CS
> 83' 944
>
> >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.
>
> 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 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.
>
>
>
> -----Original Message-----
> From: s-car-list-admin at audifans.com
> [mailto:s-car-list-admin at audifans.com]On Behalf Of tblack
> Sent: March 3, 2003 3:51 PM
> To: jimk at spotgraphicsinc.com; Randy Reimer
> Cc: serge411 at speakeasy.org; s-car-list at audifans.com
> Subject: Re: [s-cars] Re: MAF foul up
>
>
> One of the car mags did a comparo of after market filters vs OEM and
> concluded that the OEM were as good as, if not better than, the after-market
> ones. In fact I recall that the filtering of dust was significantly worse
> with the non - OEM replacements. I personally would not use any other than
> the OEMs.
> My $0.02
> Tom Black.
>
> > If there are quantifiable
> > results, please post 'em.  There's no real difference in the seat of the
> > pants analysis, does the dyno tell otherwise?
> >
> > - I've never seen any, and based on my experience, would probably never
> again
> > buy a non-stock type filter for an otherwise normal street car no matter
> what
> > a dyno shows.
> >
> > Jim
> >
> >
> >
> > _______________________________________________
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>
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