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Valve cover PCV system modifications

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Old 04-20-2020, 11:48 AM
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Default Valve cover PCV system modifications

I’m working on my vvt valve cover crank case pressure ventilation system in preparation for boost.
So far to my understanding is as I have diagramed below.
There will also be pure copper scrubbing pads inside Cavities 2&3
I plan to vent the port(s)? Using an exhaust gas scavenging system.

Please also view my thread on porting a Squaretop intake manifold:
https://www.miataturbo.net/engine-pe...3/#post1567858

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Old 04-21-2020, 08:03 AM
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Why are you blocking the port on the left (normal PCV) and removing Cover1?
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Old 04-21-2020, 08:08 AM
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Originally Posted by Rallas
Why are you blocking the port on the left (normal PCV) and removing Cover1?
Yeah, that's a bad idea. That is additional venting capacity which will be needed if adding forced induction. Both sides should go to a vented catch can.
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Old 04-21-2020, 09:21 AM
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Originally Posted by sixshooter
Yeah, that's a bad idea. That is additional venting capacity which will be needed if adding forced induction. Both sides should go to a vented catch can.
Is the pcv/intake side open under boost? I was working off that it was closed anyway so why not shave that side completely and expanding all other ports would be an increase in venting.
Im also not interested in venting under my hood.
An exhaust scavenging system will pull vacuum for free and keeps oil and other things out of intake while also reducing crank case pressure.
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Old 04-21-2020, 10:15 AM
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Originally Posted by Frofro97
Is the pcv/intake side open under boost? I was working off that it was closed anyway so why not shave that side completely and expanding all other ports would be an increase in venting.
Im also not interested in venting under my hood.
An exhaust scavenging system will pull vacuum for free and keeps oil and other things out of intake while also reducing crank case pressure.
PVC side should have a check valve inline, to allow venting under man. vacuum, but closed during boost, if leaving a working PVC. If adding catch can (s), may be different, depending on how you set it up.
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Old 04-21-2020, 10:29 AM
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In the setup proposed by Six, neither line can see boost, as both are venting to a catch can (which, if sealed, can be in vacuum).

Nevertheless, I am not a huge fan of having oil (even fumes) in my exhaust, partially because I have experience of an oil-induced fire. Would be much more inclined towards a dedicated pump, but I am unsure of the flow rate required in such an application.

Or just VTA.
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Old 04-21-2020, 10:55 AM
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Originally Posted by HarryB
In the setup proposed by Six, neither line can see boost, as both are venting to a catch can (which, if sealed, can be in vacuum).

Nevertheless, I am not a huge fan of having oil (even fumes) in my exhaust, partially because I have experience of an oil-induced fire. Would be much more inclined towards a dedicated pump, but I am unsure of the flow rate required in such an application.

Or just VTA.
Thanks for the correction HarryB!
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Old 04-21-2020, 11:13 AM
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Originally Posted by Frofro97
Is the pcv/intake side open under boost? I was working off that it was closed anyway so why not shave that side completely and expanding all other ports would be an increase in venting.
Im also not interested in venting under my hood.
An exhaust scavenging system will pull vacuum for free and keeps oil and other things out of intake while also reducing crank case pressure.
Originally Posted by Rallas
Why are you blocking the port on the left (normal PCV) and removing Cover1?
Originally Posted by HarryB
In the setup proposed by Six, neither line can see boost, as both are venting to a catch can (which, if sealed, can be in vacuum).

Nevertheless, I am not a huge fan of having oil (even fumes) in my exhaust, partially because I have experience of an oil-induced fire. Would be much more inclined towards a dedicated pump, but I am unsure of the flow rate required in such an application.

Or just VTA.
What about venting to under the car? I know thats a no no in some places, and is probably not ideal for the rest of the underside staying clean, But If I could get a similar Venturi system that I was going to use In the exhaust I could stick it in a high flow area of the undertray
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Old 04-22-2020, 10:50 AM
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If you go to a properly baffled catch can with large enough hoses, fittings, and ports to slow the airflow you will get little or no oil propelled into the can and out of the breather.

I run larger diameter hardware from both sides of the valve cover to an Allstar can at well over 300whp with maybe a teaspoon or two of oil per track day. Track day = lots of WOT near redline at 21psi.

I don't smell oil vapor when driving around town. If I did I might let a large diameter breather hose hang down from the catch can below the subframe under the middle of the car like diesels do, but it's not an issue for me.
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