Topic: NA PCV routing, check valves, and Y's.

[darthekai]

Some people say high blowby means you should change your oil viscosity due to worn rings.
I was just today trying to figure out why the Grimmspeed AOS has 3 ports... I think probably the same reason you left your cam vents: so the blow-by doesnt end up being sucked down into the cams and re-entering the system. They've probably made the cams really well segregated and somehow baffled in both directions? 

I'm with you, It should be mostly combustion gasses coming out way up there at the cam vents, and they shouldn't be coming out that violently. I will probably end up teeing them and drill/tap my intake pipe. Then AOS the PCV.

Heres what I dont understand: why on earth did subaru make that Y connection on the PCV? I'm PRETTY SURE it's to be able to draw fresh air into the crankcase OR to be able to vent with the IM pressurized... (see poorly drawn paint pic). With a closed system like you have, doesnt the 1way valve (the PCV valve) prevent this from happening?  would this need to happen?
im sure subaru engineers aren't dumb..
What I imagine with your system (and lots of other people's, obviously) is the crankcase pressuring up, but youre still on boost, so the IM is pressured up more. This keeps the PCV closed and therefore zero air moves through the system. the crankcase is not vented, and pressure continues to grow.



MAYBE what I should do is Tee the exit (fresh) line from the AOS, run one side to the PCV, and the other to my intake, downstream of the cam jobbies.

[Way_Gone]

MAYBE what I should do is Tee the exit (fresh) line from the AOS, run one side to the PCV, and the other to my intake, downstream of the cam jobbies.

Not a bad idea, and I considered doing the same thing. At the end of the day, like you, I couldn't come up with a good enough reason to vent the air back into the intake. I really don't know why Subaru did it and I think (not supported by factual knowledge) that they changed this in later versions of the EJ20, that it no longer T's off the crank and recircs back into the intake... I'm no engineer, but it doesn't make a pile of sense to me... Also, it's a GREAT way to blow oil into your intake- PRE turbo... *facepalm*

[seat safety switch]

Anecdote time:

On my TS I had savage blow-by, enough to pop the oil cap off if you loosened it to half a thread at idle. Replacing the PCV solved this blow-by and produced the expected amount of idle vacuum.

Non-turbo cars don't have that Y so I'm almost certain that it's for boost (in the same way that the brake booster hose's is different on turbo cars; either they add or modify the existing one-way valve to prevent the car from pushing crankcase pressure into the vacuum-operated brake booster - fyi, that's one thing you'll have to add to your turbo conversion if you like power brakes).

[darthekai]

The internet has told me that the booster already includes a one way valve in order to maintain the highest possible vacuum. Sorry to derail.
Non turbo cars DO have that y, it just goes to the filter box...
At least my obs does.
We need that grimmspeed dude in here to serve up some knowledge.

[seat safety switch]

Continuing the derail: I know the part number is different between the turbo and non-turbo cars, so maybe the valve is stronger on turbos.

My 2.5TS doesn't have the Y, just one line from the intake manifold to the PCV. Same with my old 97 OBS AFAIK. The OBS had crankcase vents that went to the airbox on each side.

[darthekai]

This is mine. The pcv is screwed into the I'm just behind the tb right by my thumb