pcv causing unmetered air behind the tb?

[in2fords]

I working on my pcv system, I am currently running a N/A vc from a 84 carb'd 2.3, it has a breather nipple on top of the filler cap. I added a catch can to the VC breather and run it to the turbo snout, same location I saw the vc breather running to on Glassmans svo. When I hook up the PCV to the stock location on the intake I have to lower my idle, it seems that im getting air past the TB thru the PCV, is this ok, does the iac compensate for this?

Im currently building a large catch can for the PCV, Im also using a brass water one way check valve as my PCV. Im broke so Im using a house water filter housing as a catch can, in my mind it should work but am I missing anything? for the vc breather Im using 3/8ths hose and catch can, for the PCV im using all 1/2" hose, valve and catchcan, this should be ok right?

[blueboss]

You need to install the correct PCV valve for the application. That Home Depot special won't work. The reason is the PCV actually meters/regulates the airflow and your "check valve" is either open or closed. I'd guess you spent roughly the same amount of money making that check valve work as you would have just purchasing the correct parts from the onset. Not bashing, we've all been there. Just sayin.....Until you install the correct PCV valve....no, this won't work correctly.

Here's a few threads of light reading of what I and others have done as well as a pretty good explanation of how pcv works in the last thread.

http://www.svocop.com/forum/showthread.php?1086-DIY-Oil-Separator-or-Catch-Can-or-let-it-burn
http://www.svocop.com/forum/showthread.php?643-Air-Oil-Separator
http://www.svocop.com/forum/showthread.php?211-PCV-Explained

[in2fords]

AAHHHH, I always just thought the PCV was a simple one way valve.
I do have a spring in the water valve I can play with to try to set a idle shut condition that still opens with higher pressure.
I wonder how much pressure it needs to hold back at idle and at what point it needs to open?
I maybe barking up the wrong tree and twidling my thumbs but I got nothing better to do right now anyway :)
Thanks for the info

The reason Im doing al this is that I was getting excessive oil in the intake and I have a STRONG overbuild gene that wont let me do things the stock way :)

[MikeFleming]

The proper turbo PCV valve will open (raise the floating thingie with manifold vacuum) under part-throttle and idle conditions. It will close (by gravity) under WOT with no boost, and will be pushed closed by any positive manifold boost pressure. It should not flow any air when closed or boost would pressurize the crankcase.

When the PCV valve is "open", fresh air comes into the top, rear of the cam cover from the front of the turbo inlet, (which is still all metered by the VAF) and flows through the crankcase into the intake manifold, after being metered by the PCV valve.

If the system is hooked up properly, there is no unmetered air. However all that air does indeed bypass the throttle plate. Base idle should be set with the PCV system connected and functioning.

[in2fords]

OK, I can do that with this check valve. I currently have the valve set up the same as stock, takes VERY little manifold vacuum to open but without any manifold vacuum it stays shut and any manifold pressure will never creep past it into the crank case.
Once I get it back together I will readjust the base idle/TPS.
Thanks, Jeremy

[Stinger]

It would seem that if you read the links posted above, you'd be doing much more than just adding a check valve. The links above discuss check valves, why they aren't the best "fix" (even though they were popular years ago), and what the proper fix/fixes are.

[in2fords]

There seems to be 2 reasons for the valve, the obvious is to stop boost from entering the case, the second is to regulate the flow of air out of the case into the intake for optimum running while scavenging at different vacuum/boost levels, both of these reasons are caused because the valve enters the intake post turbo and TB right?
I can only assume the reason they picked that spot is because of the high vacuum during idle? at anything above idle the snout of the turbo would see the same vacuume as behind the TB wouldnt it?

It seems if I simply route the line to pre turbo it would eliminate alot of my headaches wouldnt it? I wouldnt need to regulate the amount coming out of the case, more is better and while under boost when it seems I would need it to draw out the most from the case it would be still be working instead of the valve being closed and relying on the VC to vent it all. all the advantages of a open set up while not getting the fumes and still getting some scavenging effect. I would drill out the snout and use a 1/2 inch hose for max flow.
Has anyone tried routing it pre-turbo?

[MikeFleming]

Read up on PCVsystems in general and pay particular attention to a Type 4 system.

At low power levels, there is no significant depression at the turbo inlet so no air would flow there except for the amount of collected crankcase pressure due ot blow-by (while there may be an excessive depression at full chat). You want a constant flow of air, except when under high throttle. This actually makes a small depression (low pressure) inside the crankcase, in the 5-20 In H2O which helps boil off fuel and water vapors and extends oil life.

For most turbo engines, and especially the Ford 2.3 OHC, the airflow amount needs to be increased for the system to work properly with mod'd engines.

[in2fords]

All right, fine, I was trying to be slick and design a cool setup but lucky you guys are here to keep me in check with reality :)
The whole reason Im doing this is cause was getting far to much oil into the intake and once in a while intermittently I would pop th dipstick on a rebuilt motor with <5K miles and close to stock boost. I tried about 4 different new stock pcv's, one of them was a oem, they all leaked under10-13 psi when tested on the bench. I tried out a valve from a tii rx7, supra and a few others and no luck, similiar results as the stock ones :(
So now I have a valve that holds the boost back, just for giggles I tested it up to 109 PSI, I was worried about the fittings bursting at that point! it holds fine and opens the other way with less then 1/3rd psi, much less but my gauge cant go any lower, i have a catchcan for extra insurance and now Im going to run both the water check valve that will stop the boost pressure and the pcv that will regulate the airflow back to the stock location in the upper intake.
This should cover everything I would think.
thanks for all the info guys, its helped to keep me planted :)