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> 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 compromise. 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 - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA *******************************