The oil system is pressurized. So Scott, you're saying that vacuum has no effect on pressure? That the vacuum is not pulling oil out of the cranks pressurized oil paths? If it is being pulled out, where is it being pulled to? Even to a dummy like me, that would seem to be apparent.
Doug
its more complex than you may think - but Scott has a legitimate point.
A vacuum is a measure of comparative pressure, and does not imply air (or fluid) movement. In a perfectly sealed container with a given volume of fluid, holding a vacuum on it will not cause any movement at all. The function of creating that vacuum will require mass movement and that is where the fun begins. If the creation of that negative pressure is a one time isolated event, the movement is going to be nominal over time. If creating and maintaining that depression requires a lot of work (leaks in the system) you will certainly have movement.
All engines are imperfect in terms of sealing, and will thus have some degree of leakage, meaning that some flow through the system is inevitable. Whether that is enough to have a significant impact on oiling and durability is where perceptions and opinions diverge. Its common to use NASCAR derived comparisons, but those folks actively manage oiling, trying to have the least possible amount of oil in some areas and to intentionally flood others - - not a valid comparison to anything normal in our world.
I do know that having a vacuum will improve ring sealing to the point that many racers will go down on ring tension and make even more power. I also know that if your clearances are a half a thou too loose nobody will ever know, half a thou too tight everybody will know....
