PCV valve for boosted engines (Page 1/4)
fierosound JUL 10, 09:00 AM
I replaced my PCV valve last year and noticed there was oil seeping past the PCV grommet.
On boosted engines you want the PCV valve acting as a check valve to stop boost leaking into the crankcase.



Under boost, the PCV should be closed (or a check valve installed inline) and any blowby gases/crankcase pressure generated will reverse flow and go OUT the inlet pipe connected upstream on the turbo/SC. There should be a slight vacuum there to draw them out.

If the PCV is not closing off flow, you've got boost passing into the crankcase that will blow oil past seals and gaskets.
In my case I had pressure/oil coming past the valve cover grommets (obviously the wrong or bad PCV).

I'm pretty sure I had an AC Delco Grand National PCV valve before I replaced it with some other brand.
It seems AC Delco has discontinued all PCV valves for older turbo applications.
eg: Grand National, Turbo Sunbird and even Typhoon/Syclone.

Of the aftermarket junk for those applications I found - you could blow through the PCV both ways (more in the "working" direction).
I think the manufacturers are just using a "close enough" PCV valve to fill the gap.

Perhaps the PCV valve from 2014 Cadillac XTS with 3.6L twin-turbo would work.
But I have't been able to find one listed to see a picture of the thing (too new - not available yet?)

I went and got a 1995 Toyota Supra 3.0L twin-turbo PCV valve from a Toyota dealer PN 12204-46020 for $17.
It's a strong steel/brass piece. Opens in the "working" direction, and a "dead stop" in the other.

You need a PCV valve grommet with a smaller hole. HELP! PN 42332 does the job.
The valve fits the stock PCV valve elbow just fine. Blow-through into the crankcase is stopped.



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[This message has been edited by fierosound (edited 09-11-2019).]

KillerFrogg JUL 10, 08:40 PM
A few other potions (not researched, but just a thought) may be from one of the turbo eco-tech engines, from the SS Coblat, SS HHR i believe, as well as the top end solstice and sky.

Option 2 may be looking at the turbo Small Block Chevy or the 90* v6 aftermarket community to see what PCV they use and see if it is adaptable.
fierosound JUL 16, 07:02 PM
I'm surprised the guys who added a turbo haven't commented on the need for an appropriate PCV valve before (not that I could find).
ericjon262 JUL 16, 07:10 PM
I use a crankcase evacuation setup the pulls through the exhaust.

http://www.summitracing.com/parts/sum-120108

make sure it's installed after the o2 sensors, and that you have a catch can to prevent pulling oil into the exhaust.
Neils88 JUL 16, 07:37 PM

quote
Originally posted by ericjon262:

I use a crankcase evacuation setup the pulls through the exhaust.

http://www.summitracing.com/parts/sum-120108

make sure it's installed after the o2 sensors, and that you have a catch can to prevent pulling oil into the exhaust.



I notice these two points for the evacuation system you used:
1. Cannot be used on vehicles with mufflers
2. Summit crankcase evacuation systems are designed for drag race use only

These may just be emission based concerns....any thoughts?
josef644 JUL 16, 07:52 PM
Any Idea what year this Toyota was? You know they are gonna ask when we go there.

And thank for the information.
Dennis LaGrua JUL 16, 10:19 PM
AFAIK, PCV valves are one way valves for the suction direction only. If they flowed both ways why would they be called a valve? You are not running in boost mode most of the time so I wouldn't worry too much about continuous crankcase evacuation.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 07-19-2014).]

fierosound JUL 17, 08:11 AM

quote
Originally posted by josef644:

Any Idea what year this Toyota was? You know they are gonna ask when we go there.

And thank for the information.



I thought the part number would cover that so there's no mistake - 1995.
ericjon262 JUL 18, 01:25 PM

quote
Originally posted by Neils88:


I notice these two points for the evacuation system you used:
1. Cannot be used on vehicles with mufflers
2. Summit crankcase evacuation systems are designed for drag race use only

These may just be emission based concerns....any thoughts?



1. The idea is that gas velocity will en-train the crankcase gasses and pull them from the the angled tubes, should still work fine with mufflers as long as they aren't super restrictive. similar to how a carburetor works.

2. Setup as a crankcase evacuation system, probably best left to the track, but as a PCV system, it'd probably be fine on the street.

3. Definitely not emissions friendly...
thesameguy JUL 18, 11:37 PM
You could always run the suction for the thing to the low side of the turbo, where there is never positive pressure. On my XR4Ti, there is an oil separator on top of the valve cover that keeps the big stuff from being sucked into the turbo. On my old 8v Saab there was a separator inside the airbox, so that big stuff accumulated there and the small stuff was filtered by the air filter. There are plenty of turbo cars out there to draw inspiration from - and virtually none of them have a "conventional" PCV valve like GM was half-assing with in the '80s. Personally, I think a catch can filled with steel wool connected to the low side of the turbo should work great. That's how I plumbed my Saab track car, and it's never given a problem.

[This message has been edited by thesameguy (edited 07-18-2014).]