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Thread: PCV and crankcase pressure evacuation improvement

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Posts: 1-6 of 6
2018-10-10 07:42:34
#1
PCV and crankcase pressure evacuation improvement
As I understand it, the PCV exists only to draw blowby gases at idle and partial throttle. At WOT it serves no function.
Now, some people have blocked the PCV off completely and just routed the crankcase blowby through the typical WOT blowby port or oil separator.
Hondas have added more ports on the valve cover to help evacuate WOT blowby gases.

With these things in mind, especially on a turbo car, wouldn't it help greatly to convert the PCV valve cover port to a WOT blowby port? I.E. plumb it into the pre-turbo intake along with the typical WOT blowby gases port (with a catch can of course)?
The way I see it, you gain the benefit of no oil deposits in the intake, a more efficient way of clearing blowby pressure/gases from the crankcase (you now have two WOT ports instead of 1, and better crankcase equalization is always a benefit), and at idle you still have a tiny bit of vacuum from the turbo compressor spinning to draw gases at idle.
2018-10-10 17:46:43
#2
Originally Posted by wildmane
As I understand it, the PCV exists only to draw blowby gases at idle and partial throttle. At WOT it serves no function.

You understand it incorrectly. Your proposal is a bad idea. You have some reading to do:
Crank Case Ventilation fully explained. (Naturally aspirated edition.)
2018-10-11 09:01:48
#3
There's no description of my specific setup in that link, and I fail to see where I'm wrong about the PCV. Maybe I should have said negligible amount of blowby through the PCV at WOT? Otherwise it's pretty useless at WOT.
2018-10-11 12:12:50
#4
I think maybe when you say "PCV" you mean the "PCV valve"?
Because the PCV system absolutely has a lot of work to do at WOT, and it does it well. It just doesn't involve the PCV valve at that point...
Maybe that's the confusion?
The PCV system also has work to do at idle and partial throttle. This does involve the PCV valve.


As for your suggested setup, what problem are you expecting it to solve? Because it sounds like an awful idea so far...
Last edited by BenFenner on 2018-10-11 at 14-29-10.
2018-10-11 15:34:49
#5
Yes, PCV valve. As the goal is to equalize (or ideally put the crankcase under vacuum - can't exactly do that all the time without special equipment) the crankcase and bring it down as close as possible to 0 positive pressure, one way to do that would be to make it easier for gases to escape the valve cover. Having bigger or more ports for venting crankcase gases inherently means a drop in crankcase pressure. My whole idea is to sacrifice idle and partial throttle performance to satisfy a substantial improvement in crankcase ventilation at manifold pressures anywhere over 0 (partial throttle to WOT) *without having to modify the valve cover.
Last edited by wildmane on 2018-10-11 at 15-40-38.
2018-10-11 17:13:44
#6
Originally Posted by wildmane
My whole idea is to sacrifice idle and partial throttle performance
As long as you realize you're making this sacrifice, sure. I don't think it is worth it, but that's me.

Maybe you could add a "T" fitting off of the PCV valve bung and keep the PCV valve on one side, then run the other side to the intake. That would retain the idle and partial throttle performance, but give you more ventilation at WOT. All without modifying the valve cover itself. I'm not sure I love this idea, but it's an idea...
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