dry sump questions

[Barry_R]

Have to agree with Foxwell on some of this stuff.  A vacuum implies a sealed (or nearly sealed) system.  Unless its putting a bunch of oil and air out of the tank breather you should not have much "movement" of oil in the crankcase.  The amount of oil thrown off of the rotating assembly and it's direction should not appreciably change.  Now to keep things in context, the type of builds using a dry sump to generate vacuum are the same folks that will be pushing the envelope on other areas - RPM, weight reduction in pistons and pins, windage control and reduction, and cylinder pressure.  This type of build will highlight anything marginal, and often the new and unusual modification takes the heat for an issue that actually originated someplace else - a part that was on the edge of "good enough" until the most recent modification pushed it over that edge.

[frnkeore]

Regarding vacuum in the crank case, you are still going to have a flow of it's continence, unless your close the 29".

The inside of a engine is a fairly large area to seal!

[gt350hr]

    The new generation dry sump pumps are very capable of pulling over 18"s of vacuum. Oil is still "spraying" (pressurized) out of all of the normal areas and at speeds high enough to oil the cylinder walls , camshaft , etc. no problem. The vacuum actually "pulls" oil out of the crank and slightly lowers oil pressure. Oil is still flowing. I haven't ever seen a piston scuff caused by crankcase vacuum. In my experience , the pins ( unless pressure fed through the rod itself) receive splash oiling or non pressurized oil from the oil ring groove and high vacuum reduces the amount of oil they get. The DLC ( Diamond Like Carbon) coating provides a VERY hard surface that is also very slippery so it survives is a low oil , high load situation. At 3 to 5 times the cost of a non coated pin , they are pricey but since they don't wear on the surface , they can be used over and over and over. The cycle life ( amount of times it can flex before it yields) is far beyond the wear factor of the cylinder walls so "long term" use actually makes them cost effective.
     Randy