Vacuum in the crankcase promotes ring seal, and makes a zero atmospheric condition so the rotating mass is not pushing atmosphere (air) out of the way. These things combined are good for about 60 horsepower in this application. The dry sump oiling system controls the oil by keeping it away from the rotating mass, and the windage is a non issue as far as turning the oil into foam because the oil is continuously sucked out of the pan back into the external tank. The oil pump is also external, and driven by a toothed belt similar to a timing belt on the front of the engine
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