crankcase evac on wet sump circle track application

rfl28 · Post by **rfl28** » Tue Oct 18, 2005 11:12 am

looking for some better ideas on relieving crankcase pressure in wet sump circle motors, other than the usual dual drivers's side breathers. has anyone tried the evac tubes w/ hoses to the headers like the drag race stuff? thanks for all suggestions and replies.

SupStk · Post by **SupStk** » Tue Oct 18, 2005 3:23 pm

Since many of my customers are drag racers, and vacumn balanced systems are the norm. I tried doing that with some of the circle track engines I've built. Although I seen HP on the dyno, it was more related to lower ring tension and oiling system work, rather than the vac system it's self. Well as with most "tuners" the first thing that happened was the collector tubes were capped off and then the PCV system was blamed for puffing oil. Rather than trying to swim up stream with these guys, I just installed more conventional rings and forgot about it. It was obvious they weren't interested because it wasn't on the winning cars.

I still think it is a good idea if approached as a package deal.

rfl28 · Post by **rfl28** » Tue Oct 18, 2005 4:22 pm

know what you mean superstock....thanks for the reply,...i 'll keep thumping on it...bob

mike walker · Post by **mike walker** » Tue Oct 18, 2005 6:12 pm

we run belt driven vacuum pumps on our 700"+ nitrous engines with dry sump systems. our current engine will carry approx 12" of vacuum at idle and pull up to 15" even at the end of a run under power. if we see that vacuum fall it is the first indicator that we may have nipped a piston or raised a ringland. I have been curious for some time why the circle guys havent explored this method more closely. As one of the previous posts states most of it is reduced drag fro be able to use lower tension rings, especialy on the oil ring. There is also some seal benefit. However, some restraint must be taken when evacuating a wet sump system. getting the oil to enter into a wet sump pump becomes an issue at higher vacuums. The wet sump pump operates by creating a low pressure area. If the crankcase atmosphere is lower than what the pump can create the result is low or no oil flow. The best i ever pulled on a header style evac system is aprox 7" at higher RPM's, which is very safe in a drag application. I am not sure in a left turn situation though.

rfl28 · Post by **rfl28** » Tue Oct 18, 2005 11:31 pm

good point mike,.... and thanks to all for the replies,..i'll keep bangin on it and if i find something interesting i'll let you guys know...bob

Joe Mendelis · Post by **Joe Mendelis** » Wed Oct 19, 2005 1:20 pm

One more thing on vac. If you lower the pressure in the crankcase it lowers your pumping losses. Some guys say that if you had perfect ring seal, lowering your crankcase pressure won't help. They say for every piston going up, one is coming down. That's right, but if you stand in a swimming pool and move your arms back and forth you are making waves and wasting energy. If you do the same thing in air your arms move much more freely because the resistance is lower. High and low pressure in a crankcase is not the same as air and water, but it makes it easier to visualize. I can't imagine why even with perfect ring seal lowering the pressure wouldn't help. It takes energy to moves molecules. Even though the pumping losses are higher to draw in the charge on the top side of the piston, it takes something to draw the air in the pan up and down the cylinder as well.