[olddog]

Originally Posted by spookypt

"Hi Matt, in NASCAR today, engines run with around 20-psi vacuum in the crankcase. Dry sump pumps have their scavenge sections designed to create vacuum. A check valve is added to suck air into the crankcase to prevent excess vacuum. Regards Marcus"

I see this mistake a lot, and don't want to see miss-education given to the next person. Don't mean to be disrespectful to anyone. I'm just a bit anal.

Vacuum is typically measure in inches of mercury ("Hg) or sometimes inches of water column ("H2O) for light vacuum.

1 atmosphere is generally accepted to be 14.7 psi, which is the most vacuum possible on earth. Since vacuum is the absence of pressure, absolute pressure can only go to zero. It is not possible for absolute pressure to be negative.