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Auto racers have sometimes put a venturi in their exhaust
connected to the breather to induce a vacuum in the crankcase. This must be done
so as not to cause a crankcase explosion by use of one-way valves, Davey
screens, etc. Stock cars run 7000-9000 rpm, F1 cars run upwards of 20,000 rpm.
Since windage loss is a function of V^2, I'm not sure that an engine turning
2700 rpm would see much benefit. There is also the issue of the pressure
differential across the piston. The low pressure will aid the intake and
power downstroke, but oppose the exhaust and compression upstroke. 'Course,
these are "Experimental" aircraft, what used to be the first "E" in
EAA!
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