That's not true at all Trevor. An oiled gauze type filter is typically
far superior to a paper filter. And gets even better as it gets dirty.
A paper filter works by mechanically trapping particals that are
larger then the holes in the paper. In industrial terms, it's a bag
house. The particles that can fit through the holes do so. As the
paper filter blinds (the holes get filled with big chunks) it increases
dirt travel through the larger holes. It also tends to rip the holes
larger as the increased vacuum pulls larger particles through the
holes that barely trapped them in the first place.
An oiled gauze filter on the other hand counts on impingment.
The air travels through the cloth weave, twisting and turning
a bit to get around the individual fibers. The particles on the
other hand, don't make the turn and get stuck in the oil. Very
small particles do get through as they can make the turns with
the air molecules. These particles are on the sub-micron level
and do not cause wear problems as a general rule. As the
buildup of dirt particles on the oil soaked cloth fibers increase,
the pathways around the fibers becomes more convoluted,
resulting in increased particle impingment. Hence, the
increased filtering efficiency with use, up to a point.
Many people to trip themselves by not understanding this,
and thinking that since they can see through a K&N filter it
must not be as good a a paper filter that they cannot see
through. But as you can now see, that is not the case
actually. So, you do not have to lose filtering efficiency to
gain air flow. It will cost you more money though.
IMO, a K&N type filter would fair well on a Spitfire, given the
extremely poor nature of the oem filter. It is extremely small,
and of poor design. Combine the K&N with a small ram pipe
to correct the defficiency of air flow patterns at the carburetor
inlet, and one could realise a substantial power increase over
stock.
>>> Trevor Boicey <tboicey@brit.ca> 09/25 4:45 PM >>>
Filtration-wise, accept that you are giving up quite a
lot of filtration compared to disposable paper, and the situation
gets worse if you don't clean and oil them regularily.
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