I send these interesting comments out whenever the air filter debate comes
up on a BMW list or a italian-car list or an autocross list or now (again) a
Dakota list:
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italian-cars-digest Wednesday, 20 September 1995 Volume 02 : Number
719
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From: Ed Hackett <edh@maxey.dri.edu>
Date: Wed, 20 Sep 1995 09:20:09 -0700 (PDT)
Subject: Air Filter Data
Here's the info I have on air filter performance. Tests were done using
SAE J726C Test Method 5-best --> 1-worst
Oiled foam Paper Oil Bath Oiled Gauze
(AMSOIL, UNI) (K&N)
Large particle efficiency 5 5 5 4
Small particle efficiency 5 4 1 2
Airflow capacity 5 2 3 5
Dust holding capacity 4 2 5 2
Load up characteristic 4 1 5 1
Backfire characteristic 3 2 5 3
Cleanability 4 1 4
3
As you can see, K&Ns are great for airflow, which is what they were
designed for. Their original application was on racing engines, where
airflow is important and ultimate engine life was of little consern. They
are not as good at filtering as paper or oiled foam types.
Personal experience backs up this data. Running a K&N in a BMW GS/PD off
road results in much more fine dust downstream of the filer than with
either the stock paper or Uni filters. Two friends raced 2-smoke MX bikes
in a desert race recently on identical bikes. One used a K&N and the other
the stock oiled foam (yes, MX bikes which are designed for max power and
to be run in extremely dusty conditions use oiled foam air cleaners).
The rider with the K&N had to stop twice and clean the K&N because it had
clogged and was choking the engine. The bike with the oiled foam cleaner
finished the race with no problems.
The other test Richard is refering to was done by a consturction company
who wanted to try and save money on filters by using K&N filters. Oil
anyalysis showed much higher levels of silica (dust) and wear in the
engines using the K&N filters. They went back to paper. (Sorry, I don't
have the article to post).
Ed Hackett edh@maxey.dri.edu The Desert Research Institute
DoD #0200 WMTC BMWRA DIOC Reno, Nevada (702) 673-7380
KotLS KotLE DotD #0003 I'm not really a chemist, I'm just one
of
BMW K100RS, Moto Morini Camel them motorsickle sonsabitches.
__=o&o>__
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C O R N I N G I N T E R O F F I C E M E M O R A N D U M
Date: 22-Sep-1995 00:31am
From: ASRT@aol.com@in@VAXB
Dept:
Tel No:
TO: SCHELLING_PM@corning.com@in@VAXB
Subject: Re: Current or potential K&N ...
The same issue was brought up on the bmw list a while back. Similar evidence
was cited of dust downstream of the filter.
I have used K&N filters on street bikes, street cars and on my Chevy 4bi4. I
have not seen the dust/grit downstream of the filters that others have
reported. The Chevy was run hard in dusty and muddy environments with
absolutely no evidence of this or performance issues due to the filter
clogging. Note that this was with a fancy chrome unit with a 14" diam. by 6"
tall K&N out in the wind, not sealed tidily in an OEM housing.
I can't categorically state that the test data cited by Ed Hackett is wrong,
but I can say that my personal experience does not match what he says, and I
am comfortable continuing to use K&Ns. After the first time I heard this, I
started wiping the intake horns of my carbs on the Corolla every time I had
the filters off, just to see if I was getting dust 'n' stuff past the
filters. Zip, nathan, nada.
There, now you have my two cents. If engine life is negatively affected by
K&Ns, I haven't seen it.
-K. (&N) Hughes
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