Small vid about PCV

TT5.9mag said

I asked because I tried a sealed crankcase pcv with a fixed orifice (under the intake manifold) and had weird oil pressure problems. When I researched it I seem to remember finding others with the same issue, and an article from good source stating that’s what was happening. Of course I can’t find it now. Regardless I went back to the previous setup with a fixed orifice and a one way check valve and inlet air metered through the throttle body and all was well.

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I have heard of this with a vacuum pump on a wet sump. In fact, I think David Reher did a tech article on this way back in 2000-2001 or something in National Dragster.

There is truth in that dropping the crankcase pressure can (and will) drop your oil pressure some. I’m not sure you can pull enough vacuum through a PVC or even pan evacs (or both) to affect oil pressure.

The oil pump functions like any other positive displacement pump, in that a pressure differential is created in the gears and that pressure difference between the negative pressure in the pump (and by extension…pun intended…you’re welcome for that free funny pun) and atmospheric pressure in the pan. Or an even greater differential if you have some pan pressure.

Im not advocating for pan pressure. It’s bad. I’ll be testing my crap on the dyno hopefully by March, or April and I will see how much actual pan pressure I can pull with a PCV and pan evacs and where the greatest pressure drop occurs. I’m sure that will be at a light load, low throttle opening when both systems are working. But I won’t know for sure until I get a chance to test it.

Of corse, the way things go around here it could be June before I see the pump.