Date: Tue, 9 Jan 2001 11:38:04 -0800
Reply-To: Alistair Bell <albell@UVIC.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Alistair Bell <albell@UVIC.CA>
Subject: Re: K&N filter
In-Reply-To: <021701c07a66$e3b337c0$9d30a2d1@wd1000086onem>
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Sheesh, this thread is getting a bit tired!
anyway, have to add a couple more points.
The K&N filter I have is not a "foam type " as mentioned in the ASME report
below. Its cotton with a wire mesh reinforcement.
I believe that the oiled filter matrix works in a combination of ways:
First as an exclusion type filter (like paper) where the pore size (or the
spaces between the fibers) determines the size of particle that is excluded.
I don't see any filter manufacturers stating the cut-off range for their
filters...What size of particle gets through the paper filter? who knows.
Anyway, for the K&N filter thsi "pore size" seems quite large.
Second, as a centrifugal type filter similar to the old oil bath set-up.
Don't confuse this with "cyclonic type filters (although they use similar
effects). What I mean here is similar to the analogy given of the tennis
ball (baseball?) shot through a forest. The key point though, wasn't
mentioned, that is the path of the airflow through the filter matrix is not
a smooth or consistent one. The poor old dust particle will be swirled
around the fibers, sooner or later (like the Porsche driver) it won't make
the corner and hit (fall out of the stream) the fiber, which is covered in
oil and thus traps the little bugger. Note that the spaces between each
fiber are much, much larger than the particle size, the particle is not
trapped by trying to squeeze through the forest, rather it is trapped
because it cant make all the corners!
Trying to make the corner! poor and inaccurate analogy...more like the
particle migrates to the area in the airstream that is flowing slower, and
that would be the inside of the corner...just as sand is deposited in the
inside bend of a river and tea leaves move to the middle of a stirred cup of
tea.
The oil bath filters work like a whole bunch of mini cylconic separators.
Granted the cyclonic separator is engineered carfully to create that special
airflow that drops the dirt, but the filter matrix (horsehair, steel wool,
cotton, whatever!) does the same thing.
Paper filters probably use this effect to sum degree too.
I once had the pleasure(?) of working with a benchtop Buchi spray drier,
spray drying bacterial cultures (quite interesting how some Gram neg bugs
take to the process!). The individual bacteria were around 2-3 microns long
and 1 micron in diameter. The dried powder ranged in size from 1 micron to
conglomerates 60-70 microns in diameter. I could trap that powder in a
simple glass cyclonic separator. It was amzing to see the powder swirl down
the outside of the separator then drop into the collection cup, the airflow
continuing up through the central exit tube (just like a scaled down version
of thsoe dust collectors seen outside woodworking shops). I'm not saying all
of the dust wass collected by the cyclone, just that it was amazing that
such small particles could be trapped at all.
So Bill, why not see if you can modify/enhance your syncro's cyclonic
prefilter? Can it be made self cleaning? (electric trap door?). See how
efficient it is in removing the bulk of the dust.
Do some experiments, generate some data!
Take air filter system off the van, hook it up to a shop vac of somthing to
generate the appropriate air flow, measure some dust/dirt/sand, feed it into
the system and see where it ends up. Come on, you're interested in getting
the best info aren't you? :)
Alistair
W
on 9/1/2001 10:06 AM, Bill Davidson at wdavidson@THEGRID.NET wrote:
> This excerpt from a post by Pensioner is the only comment in this thread to
> refer to any kind of actual testing (as opposed to marketing hype, theory,
> and belief) of the K&N filter. I don't know if the information is accurate
> or not, but I think it is worth reposting the quote:
>
> "ASME (mechanical engineering society) did a study years ago for diesel air
> filters for earthmoving equipment. They found the best is a folded treated
> paper system FOLLOWED by an oil bath system (a la aircooled bugs) AND
> regular maintenance. They rated the filtration properties of the K&N oiled
> foam type as poor. They were not concerned with HP/MPG only with
> preventative maintenance."
>
> Please, I'd love to believe the K&N is both higher perfomance AND better at
> filtering out smaller particles than paper filters.... If someone has actual
> data to support that PLEASE post it to the list.
>
> Bill Davidson
>
