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Crank case ventilation and negative pressure

Post 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 ... re-part-1/

Actual dyno tests wti various crank case pressure setup
Dr. Alban
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Re: Crank case ventilation and negative pressure

Post by KevinR »

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Joined: Fri Oct 23, 2015 4:15 am

Re: Crank case ventilation and negative pressure

Post 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.
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