brian damage wrote:
Absolute tosh.
The oil-coated K&N style filters usually give better filtration than their
paper counterparts !

On Tue, 4 May 2004 09:38:31 +0100, Nom <Nom (AT) Somewhere (DOT) Somewhere> wrote:



Not according to any tests conducted by anyone other than K&N.
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In article <c77kps01cvq (AT) news1 (DOT) newsguy.com>,
Nom <Nom (AT) Somewhere (DOT) Somewhere> wrote:
Why would car makers fit inefficient air filters? Do Land Rover etc use
K&N for their 'safari' vehicles?

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Dave Plowman dave.sound (AT) argonet (DOT) co.uk London SW 12
RIP Acorn

In article <c77kks01csl (AT) news1 (DOT) newsguy.com>,
Nom <Nom (AT) Somewhere (DOT) Somewhere> wrote:
Of course. How else do you get the car to change down? ;-)

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Dave Plowman dave.sound (AT) argonet (DOT) co.uk London SW 12
RIP Acorn

"Dave Plowman" <dave.sound (AT) argonet (DOT) co.uk> wrote

I don't know about modern crap, but take a look at your SD1. Bet you'll find
at least one part, be it even a nut or a bolt, that would only have cost
pennies to increase quality.

Paper filters are damned cheap, and flow well when new. They also clean the
air nicely too. But they're probably not the best at both (I'm sure they're
not the best for peak flow). However, they are the best for being able to
sell a new one every service, and for saving a couple of quid a car, which
adds up to a whole lot of cash if you're selling a million of that model!

Something I read in the Vizard bible went along the lines of there's little
difference between a new paper filter and a new/ cleaned K&N (the K&N was
slightly better, IIRC), but the real difference comes into play after a few
miles in dusty conditions. The K&N was still flowing at a fairly high
percentage of it's "when clean" figures, whereas the paper element was
clogged up to buggery. Not that Vizard described it quite like that of
course

My take is aftermarket filter element for a small increase in air flow, and
cost savings by servicing rather than replacing it, or a paper element if
you don't mind buying a new one every so often. Or a replacement filter and
case if you just want to increase the noise your engine makes.

Apparently on date Tue, 04 May 2004 11:23:48 +0100, Dave Plowman
<dave.sound (AT) argonet (DOT) co.uk> said:

An equally good question might be why K&N specialise in producing inefficient
air filters, if they do so, which doesn't seem too obvious a conclusion.

As far as I am concerned, air filters have two basic properties, they filter
out dirt and permit through air. As a first cut, I would expect a filter that
was good for airflow, to be bad for filtering, and vice versa. Therefore,
removing the air filter altogether is best for power, but dumb because a single
grain of sand being sucked into a cylinder means it will scratch up and down
the liner until the piston isn't doing anything much for you.

Judging only by the seat of my pants, K&N seem to be slightly less restrictive
than most of them, and I'd reckon all filters halt particles of sand and that,
so realistically it's a subtle balance between a little more airflow and a
little more (non-critical) dirt to go with it, meaning more cleaning is
necessary. Must admit, I've not actually measured the pressure gradient over a
range of filters directly, which would probably give some sort of objective
measurement.

I would imagine there are hugely expensive types of filter used in top
competition, but a search didn't turn many up so I dunno how much significance
the filter has, might be very small, in which case the point about K&N and foam
and whatnot is you can clean them from time to time instead of having to buy a
new one, a worthwhile feature even if there is no other difference.

The other observation, which is quite key, is a filter OEM probably isn't
suited to a modified engine and you have to come up with some alternative means
of getting higher airflow into the engine. Conical filters are a convenient way
to achieve this quite easily, so in a sense you have a lot less choice once you
move away from a standard engine.

Dave Plowman wrote:
I use my arm, cos my car's a manual

Dave Plowman wrote:
They don't.
Paper filters are "good enough" - why would the car maker fit hugely more
expensive oil-coated foam/cotton elements ?

Nope - why would they ? Paper filters do the job fine, providing they're
changed regularly.

Just because a paper filter is "good enough" at filtration, doesn't mean it
can't be improved though

Duncan Wood wrote:
Care to illustrate such tests ?

All the write-ups I've ever read, have said K&N's oil-coated cotton is very
good at filtering. The same doesn't apply to the foam-type filters used by
Pipercross and the like though.

AFAIK Aston Martin use them!