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  #1  
Old 08-10-2010, 02:13 AM
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Default For jEstEr?...PCV

Here's my understanding of the AVCS engine breather/PCV arrangement......


All the early turbo and NA engines pre-avcs use the same PCV system that fundamentally requires low resistance air flow through the oil return ports in the bottom of the heads.

Add AVCS and now this is a bit more difficult due to the increased oil congestion in the heads (spray from the avcs solenoids) - so Subaru had to allow for an alternate low restriction air flow path between the heads & crankcase...... That path being the larger of the 2 fittings on the heads & the one on the crankcase....Hence no baffles.

Originally on your engine there were three ports directly plumbed into the three main oil sections of the engine (the larger of the two ports on each head run to the central crankcase fitting). <- You need these, they ARE NOT PCV lines!

There isn't supposed to be any oil separation occurring on those lines, they are there simply to allow the blow by gases to equalize between the heads & the crankcase. They don't vent externally either via the PCV or back to the intake on the OEM set up. These are completely separated from the positive crankcase ventilation system.

They are the top lines in this diagram (the 2 head breathers feed into the central crankcase fitting):




Now the actual PCV system!

The PCV to manifold hose is supposed to feed off the fitting (actually the PCV valve is housed inside here too) in the rear of the block (driver's side) as your specific block has the oil air separator built into it & the PCV is attached to the separators outlet.

(Item 4 is the oil air separator cover in the image below)



The Pcv is here (inside the rubber section below the square based fitting):



This is the actual PCV assembley (P/n:11815AB790) and what it looks like! :
(This is the OEM Subaru 2005-2006 Legacy GT PCV Valve & Hose Assembly.)



Is this the fitting that your not currently using?........It's the root of all evil on the Legacy forums (they are prone to freezing open)!

This system is totally Unlike the non AVCS pcv system that has a pcv valve screwed directly into the inlet manifold.

I'm not sure if I've explained it very well but I'd be happy to clarify anything as needed.


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Last edited by Rossco; 08-10-2010 at 02:40 AM.
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Old 08-10-2010, 07:52 AM
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This is what he needs to really do..


heres a write up from my mate on NASOIC about his setup:

Okay guys, heres a quick drawing of how the simple separator works.



You can see the 3 inlets, the dividing wall. The wall needs airspace above and below. Just make sure that the inlets are pinting at the wall and not the top of the can else the oil can be thrown over the top of the dividing wall.
The return to sump at the bottom and the VTA. The return to sump must be -10 or larger and plumbed back in below the oil level. This is so the crank case pressure cannot force its way bak up the oil return. Some people put a one way check valve in the return line. Some dont.
You need to have the separator mounted as high above the engine as possible. This makes the system work best.



Here you can see that the 2 large 16mm rocker breathers and the centre crank 16mm are tee'd together. The 16mm rocker breathers are unbaffled in the rockers so are the 2 most likely to throw oil out. having these joined together balances the system and equalises pressure across the system. The PCV is deleted and blanked.

The 2 smaller rocker breathers are internally baffled and are so less likey to throw oil anyway. These go to an inlet each on the separator. The 20mm large rear crankcase breather also goes to an inlet on the separator. The separator wants to be approx 1.5 to 2litres in volume.

Hope this helps you guys a bit.

Feel free to give me your thoughts. You may like it, you may not. But there are loads of cars over here running this system and on all but out and out race cars running slicks and moster power, it works very well.
On the higher powered race cars they use 2 separators and have all lines going to the separators and have 2 returns to sump. The separators are linked with a joining hose to balance breathing. But on all of them the PCV is deleted.
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Old 08-10-2010, 08:16 AM
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cheers queers
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Old 08-10-2010, 08:22 AM
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In the picture you've posted Tino they are still using the larger rocker outlets Tee'd to the air balance port in the centre of the case (the lower hoses in the pic above) and that was my point.

Using the smaller (baffled) head ports & pcv port (baffled) minus the valve is the logical way to vent to the catch can. But you need the balance lines tied together separately to the catch can system if your running the AVCS, to provide the crankcase gases a path of return from the heads to the block/sump..
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Old 08-10-2010, 09:12 AM
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Are you able to run those balance lines with the manifold still on?
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Old 08-10-2010, 09:20 AM
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I don't see why not Russ?
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Old 08-10-2010, 09:46 AM
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Okay..

I have AVCS heads but with non-AVCS cams fitted (no AVCS cam gears, the solenoids are just connected to provide oiling to the cam journals), and that bigger port seems to be unused on my heads..

DO I need to connect them as per above?
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Old 08-10-2010, 09:49 AM
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Car is static display... so you should be fine...

You must be getting worried with that 50thou service coming up...

Brent.
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Old 08-10-2010, 09:50 AM
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Quote:
Originally Posted by Rossco View Post
I don't see why not Russ?
Sweet. Im planning on doing this with a nice catchcan soon.
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Old 08-10-2010, 09:53 AM
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Quote:
Originally Posted by sleepR View Post
Car is static display... so you should be fine...

You must be getting worried with that 50thou service coming up...

Brent.
It's done more km than that.

Jokes getting pretty old too, and used by many people.. time for some new material!
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