PCV on inlet manifold?
 

Ive got another phase 1.5 manifold that I am preparing to paint after some minor flow work. It was supplied to me by Tone Loc, cheers for that, and still has the PCV under the TB area. Can I vent this to atmosphere and block off the manifold? or would it be better to route it to a catchcan and then back again?

Opinions please.

Blocked of my pcv, and run all other breathers vta.

as above, block it off, block the pipe at the other end near where it exits the crankcase - then route the remaining c/case breather and cam breathers to atmosphere (via a catch can if you prefer).

Which 'remaining c/case breather'? You just blocked the only one off at the crankcase breather exit, if I've read that right?

No the breather tube (plastic) exits from the crankcase into a T as standard. 1 leg goes to the PCV, the other goes to the inlet pipe.

Block the PCV one and re route the other to the catch can.

here is a before and after pic i did for a guide on another forum.

G is the breather in the first pic, you can see the two pipes exiting. In the second pic the pipe that went from the breather to the inlet pipe now goes off to the catch can (meets uop with cam breathers before hand)

obviously the two 'holes' in the inlet pipe after the mod need to be blocked.

http://img.photobucket.com/albums/v3...ark/catch1.jpg

http://img.photobucket.com/albums/v3...ark/catch2.jpg

Just as an aside, instead of just bunging the PCV pipe up, i removed the PCV and pit a plug in the hole. 1/4" BSP IIRC. looks a lot neater.

nice drawings mark:lol1:

:o

i know, a bit blue peter, no scanner so had to take a pic of them afterwards:wonder: .

Cheeky fecker:lol1:

1/4"bsp?......... wasn't it 3/8" mark? i think thats what it was listed as on your guide..... i located one but havn't fitted it to mine yet to confirm

Hold on , i will go and check in the stores! back in 10:lol1:

Definetly 1/4" BSP (OD is 12.3mm - 3/8 is 15.8) Rigga. obviously i made a mistake on the guide. Just pm me on P1woc and i will get one off to you FOC;)

Here you go silent running - a pic says a thousand words:)

http://img.photobucket.com/albums/v3...k/DSC00348.jpg

Yes, sorry my mistake, I was thinking of my 'green' arrangement - PCV system to the underside of the TB is still connected for part throttle running, with the other port that goes to the inlet normally, intercepted with a catch tank, but still plumbed back to the inlet eventually. And it's collecting a hell of a lot of oil vapour too.

Erm, so block it off then? lol

I already have the other breathers done but not this one.

Well the crankcase-to-PCV-to-throttle body route is only used when the manifold's in vacuum / light throttle. Soon as you give it any throttle and there starts to be boost pressure present in the manifold, the PCV shuts and then oil vapours divert directly into the inlet manifold instead.

So it comes down to whether you want to vent the small amount of crankcase fumes whilst on light throttle, or whether you want them to go through the manifold and get burnt off as Subaru intended. Personally I kept that bit standard because IMHO it makes absolutely no difference to the performance or longevity of the engine having it plumbed in. The problem area is the crankcase-to-inlet route where significant amounts of oily vapour are dumped through the inlet on full throttle, which then find their way into the vacuum piping, the turbo, the intercooler, the throttle body etc. That seems to be what needs a catch tank, not the PCV route. If you block that PCV route, are you going to vent the crankcase end or let it blow into the inlet directly? The PCV is what keeps oil vapours out of the inlet tract under part throttle conditions AFAIK.

My reason for doing this is down to the fact that the manifold I bought has lots of oily deposits that have come in from the PCV. I think you will still see some deposits with the PCV.