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Crank case ventilation and negative pressure

Posted: Mon Mar 29, 2021 7:20 am
by Zamani
I think there's merit in creating negative crankcase pressure. But maybe it has more to do with seal longevity as opposed to "free horsepower". I don't like the fact that hot crankcase air gets into the intake. For a road car, emissions forces you to do this, but for an off-road car, I question the need for routing hot oily air back into the intake.

Article relating to crank case pressure
https://dsportmag.com/the-tech/quick-te ... re-part-1/

Actual dyno tests wti various crank case pressure setup
https://youtu.be/2fg0eZzRNZI

Re: Crank case ventilation and negative pressure

Posted: Sat Apr 10, 2021 2:25 pm
by KevinR
Interesting.

Re: Crank case ventilation and negative pressure

Posted: Thu Apr 15, 2021 1:47 am
by 105gta.
Couple of things to keep in mind.
You need to maintain zero air flow though the engine. As in not apply a vacuum source and have an atmosphere/open outlet somewhere. Needs to be sealed.
Otherwise you’ll empty your sump of oil real quick.
To be beneficial. You need way more than the -2.2psi in the video. Generally north of -8psi or more accurately 18-20 in/hg
But the real benefits are seen at the top end of the rev range and in the potential tuning.
Having a vacuum stops the oil mist entering the intake on the factory setup. So no mixture dilution risking detonation, also a neg pressure means no oil leaks. It’ll suck air in before oil falls out. 😉
It’s tedious and time consuming to build a proper system outside of a dry sump setup. But can be done and has the same power increasing benefits of a dry sump but none of the oil surge protection.

Re: Crank case ventilation and negative pressure

Posted: Tue Jun 15, 2021 5:29 am
by gtv-racer
can't you get away with a good oil seperator?

Re: Crank case ventilation and negative pressure

Posted: Thu Aug 26, 2021 9:02 am
by Zamani
Which do you recommend? Some of the stuff I see for sale don't have the right mechanical design to separate oil from the air and they're super expensive. Some of the industrial oil separators I see online should work well, but they need to be adapted to the engine bay.