Think of a bell jar. You can create a vacuum in the jar because it is total
sealed but the exhaust of the vac pump is vented to atmosphere. If your
engine is totally sealed it acts like the bell jar example. Your dry sump
pump is the same as a vac pump. Only it is releasing both crankcase air and
frothy oil to atmosphere in your tank (due to the vent). However, you are
re-introducing pure oil (hopefully) into the sealed engine. As long as the
dry sump pump has a greater suck volume than the TOTAL volume of oil (and
air leaks) being re-introduced to the engine, you will be able to lower the
pressure inside of the engine. (No check valve needed) This lower pressure
(partial vacuum) also helps the oil aeration problem. Less air bubbles are
formed in a partial vacuum than in atmosphere conditions. I have seen dry
sump systems run either at atmospheric pressure or under partial vacuum. You
greatest benefit will always be derived with a partial vacuum system. Moroso
diagrams do NOT show vented valve covers.
http://www.moroso.com/articles/articledisplay3.asp?article=AboutDrySumpSyste
ms.html
-Elon
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