Gnarly 928

I have a 6.4 liter race car, running fairly high compression, new internals and individual throttle bodies. Dynos at right around 575 RWHP. The machinist involved in the build is a big advocate of running a vacume in the crankcase..says it is good for significantly more HP without any downside. My mechanic/engine builder has no experience with doing this, but respects the machinist's knowledge.
So, I have, also, a brand new very stout vacume pump to power my brake boost system. This pump sits on the passenger side floor, right now and cycles on when I draw vacume by braking. I'm thinking it would be pretty easy to tap into the oil pan and draw a vacume down there, since I have the pump already and plenty of fittings and SS line...but, would it be worth the trouble, and if so, what vacume pressure should I set for the sump area?
Thanks for input in advance.
Don Hanson

PorKen

Consider that the pump is pulling from a basically open ended source, so you need a pump that will handle a lot of volume, and nasty oil/water/gas vapors. You'd need a serious electric pump, and a separator before the pump. I've read in different places that 14-15" mercury is said to be the safe limit with a wet sump. Some places say 10-12" is a good target.

I have oft considered getting a belt driven pump from this place, some good info here too: (Vacuume Pump Guide)

One of these might just pull you over 600!

Gnarly 928

Thanks for the numbers.
Don Hanson

slate blue

Hi Don, I bought the pump below on Ebay, we have pulled it down and it is perfect. I paid $415 for it. I am converting it to be a 4 stage vaccuum scavenge pump. So it wont supply any pressure. I think there is two benefits, one is the increased power, my guys have said when they have put vaccuum pumps on engines similar to yours, they have seen an extra 25 hp on the dyno. The other thing is windage in the 928 engine with its shallow sump. I will be buying some crank scrapers soon. I am looking for extra bit of power that is being wasted. Windage must be bad on the track.

shaaark89

ignorant question here, but is this something that can benefit forced induction motors?

m21sniper

It should benefit any motor.

shaaark89

do you think that a vacuum pump could effectively lower the crankcase pressure while under boost? i would expect with the volume of air being pushed into the motor that the pump would have to move a sh*tload of air to have much effect.