TwinTurbo.NET: Nissan 300ZX forum - Yes, that is quite a bit different. :) I actually saw a
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Subject Yes, that is quite a bit different. :) I actually saw a
Posted by Ash's Z on April 21, 2011 at 7:58 AM
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In Reply To Maybe I wasn't very clear. posted by spdrmn15 on April 20, 2011 at 09:28 PM
Message vehicle when I was up in Delaware some years ago at a dyno facility which had a vacuum pump belt driven to suck down the crankcase. It actually adds a significant bit of power because it creates a larger pressure differential on the pistons (lower pressure underneath the piston = more power), not to mention it reduces the density of the gases within the crankcase. They were pulling 15" Hg of vacuum on the crankcase with that vacuum pump. :)

Unfortunately in the Z's PCV system, the only thing creating a vacuum on the crankcase when performance is considered is at the turbo inlets and this only occurs when you are in positive manifold pressure. Even still, you would only be looking at a few inches of vacuum at best. And even even still, the jetting in the hoses between the intake valve covers and the turbo inlets would likely prohibit much of the suction within the inlet from producing much of a vacuum in the crankcase.

Perhaps one consideration that would be worthy here is to use a smog pump as a vacuum pump on our engines. :) Smog pumps would positively ventilate the crankcase and they dont feed back into the engine intake.

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