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Re: K&N Filter and Chip in a 1993 318i

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> I purchased both parts from a local shop. The K&N filter cost was
> $44 Canadian (.73 US = 1 Canadian) and arrived after a couple of
> days. The performance increase was not noticeable except that
> subjectively the engine felt smoother and a bit stronger above 5900
> rpm.

I recently installed an AMSOIL foam air filter into my 528e. And I
feel thrilled by the experience. My car would be a real loser at
low rpm's and this definitely made a big difference.

As many of you may not know what this stuff is, I will try to explain.

OK, the paper-based air filters (OEM and Fram etc) essentially do a
very good job at filtering - they remove even very fine particles.
However, in the process, the offer a lot of resistance to the flow
of air.

K&N uses an oil-wetted gauze filter - the flow is much improved (due
to reduced air resistance), but the filteration performance is not
as good.

AMSOIL uses an oil-wetted polyurethane foam filter. This has flow
characteristics much better than the paper type, and quite close
(but a little worse than) K&N, and filteration characteristics much
better than K&N and quite close to (but a little worse than) paper.

But more important, it seems that the foam type filter has a much
higher capacity to hold dust without getting clogged, so in the long
run, it outperforms both the paper-based filters and oil-gauze type
filters. (And the oil they use is much more sticky than K&N.)

And at 1/2 the cost of K&Ns too. (I got mine for something like $28
including shipping.)

Ahsun
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Ahsun H. Murad (murad@domain.elided)
University of Maryland, College Park, MD