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Re:dry element air cleaner

> On Fri, 19 Jun 1998, Jim Adney wrote:
> +
> + Gee, hope we weren't too brutal!
> +
> + I think it is the Bill Fisher book that refers to how good the stock
> + air filter really is.  (As opposed to how poor most people think it
> + must be.)
> 	I'll never know why people automatically assume that oil-bath
> air cleaners are no good.  <shrug>  Obviously, they've never seen
> under the hood of a big Caterpillar or something, and those things
> live in really dirty dusty conditions as a rule..

I suspect that most people never think about the importance of having 
an air cleaner that does a good job at cleaning.  This mistake is 
made by the Hi Performance people who think they don't need to worry 
about clean air, and just want to maximize air flow.  It turns out 
that the oil bath air cleaners really do present a rather low 
impedance to the airflow.

There were some tests done a few years by some racers where they 
discovered that running their race car with just velocity stacks 
(this is on a "nice" clean air day) gave more power at the start of a 
race, but resulted in a loss of 10 HP by the end of the race that was 
not experienced by the same car using a good air cleaner.  The 
overall effect was that the car was more competitive with a good air 
filter.  The normal amount of grit in the air, on the track with 
other cars around stirring things up, caused enough extra wear of 
pistons, cylinders, and rings to make the velocity stacks a poor 

I think the Bill Fisher book talks a bit about the airflow impedance 
of different types of air cleaners and points out that the OE oil 
bath cleaner turns out to be excellent.

Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

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