Thread: Turbo crankcase venting

I am running a blowthru setup on my B14, and have a breather filter on the "T" on the valve cover. I don't know why I didn't think of it earlier, but I realize now that my idle issue is due to this - it's taking in unmetered air through the PCV valve.
How are other's that are running blowthru setup's venting the crankcase/valve cover? Is there any down side to disconnecting the PCV from the intake manifold and venting that to a catch can w/ the "T" also?

It would be a bit ghetto, but you could put a large one-way check valve before the vent to atmosphere to prevent drawing any air in to mess up your idle, and still let air out.

I imagine most of them are venting to atmosphere through a catch can. But that doesn't really solve the idle problem. I'm betting a lot of them might not even have any idle issues?

Yes. That will prevent you from having any vacuum in the crankcase during idle or cruising.

I'm sure you've seen this thread, but just in case someone else searches and finds your thread in the future I'm going to link to this here: http://www.sr20-forum.com/forced-induction-turbo/44727-crank-case-ventilation-fully-explained-turbocharged-edition.html

Thanks for the link, I was looking for info like that. I'm thinking about running the "T" in the valve cover and the PCV straight to a catch can and then running that to the intake piping before the turbo. This way it's not sucking in unmetered air, and it still have a vacuum in the crankcase from the turbo inlet.

I see two problems with your proposed solution.

1) There may be oil still present in the ventilated air that can eventually contaminate your MAF sensor and reduce or inhibit it's functionality.
2) You will never have a strong vacuum in the crankcase because the turbo inlet doesn't ever produce more than a weak vacuum at best. Installing the pipe at a 45 degree angle does help some though.

Why not at least leave the "PCV" section on the left side alone, and recirculate the "T" from the valve cover into the turbo inlet after another catch can?

I would still be sucking in unmetered air through the pcv then since I'm running blowthru. I need to keep only metered air going in, as the little air going through the PCV now is wreaking havoc on my idle, especially when pushing he clutch in after cruising.

I have 2 thoughts on how to correct this issue.

1: take out the pcv valve, replace it with an open fitting w/ the same threads, run that line and the line from the "T" on the other side of the valve cover to a catch can, and then run a line from the catch can to the intake side of the turbo. This will keep all unmetered air from entering the intake manifold, and should be plenty free-flowing to allow all blow-by and pressure to escape the crankcase, as well as possibly creating a vacuum at idle and partial throttle.
The only flaw I see with this is that there is no vent to allow fresh air into the valve cover if a decent vacuum is created at idle.

2: Leave the breather filter on the "T" on the valve cover, and run the line from the pcv valve to a catch can, and then to the intake side of the turbo. This will allow fresh air to enter the valve cover, but will not go into the intake manifold, eliminating the unmetered air issue.
The possible issue I see with this is if there isn't enough vacuum created to open the pcv valve, the system won't flow as well as option #1, which I assume will perform better when under boost and excess blow-by is generated in the crankcase.

Any thoughts on the better option, or other ideas? I'm leaning towards option #1. Any help would be greatly appreciated.

I simplified my setup by removing factory pcv/oil separator setup all together. Then welded fittings to the valve cover where the factory fittings used to be, keeping the baffles intact. After that I plumbed (2) #10 lines from the valve cover to a catch can. Then a #12 line from the valve cover to the block in place of the oil separator. The system vents to atmosphere and doesn't see vacuum...but works just fine.