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  #1  
Old 07-10-2007, 01:10 PM
jsteele22 jsteele22 is offline
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Want to clarify PCV plumbing...

Hi,

I bought an EG33 from a wrecker and I'm getting ready to re-assemble it. It came with intake manifold and throttle body, but nothing further upstream. And of course my notes from way back when I disassembled it are inadequate. I'm trying to figure out how to hook up the PCV system and have a few questions.

1) the hoses from the cam cover breathers - can they simply be plumbed into the air intake somewhere before the throttle body ? (I'm not using the stock intake, gonna fab something up.)

2) The only port I see in/out of the crankcase is the roughly 1/2" one at the passenger side rear, connecting into the oil/air separator. This makes sense for an output, but I don't see a seperate port where fresh air would be input into the case. Is there a seperate fresh air input port somewhere I'm missing, or does one port do both ?

3) In the parts diagram at subaruparts.com, there is a part (#11821) called "Connector-purge control valve". I can't find this part in my pile, and I don't quite get what it does : is it simply a connector, or is also a valve ?

4) Is this part the answer to question (2) ? Does it take fresh air from one hose and let it flow into the crankcase, and then direct dirty air coming out of the crankcase through the other hose into the PCV valve ? It looks as if it fits onto the port at the passenger side rear of the crankcase, but it's kinda hard to tell from the drawing.

Thanks for any help you can provide,

Jeff

Last edited by jsteele22; 07-10-2007 at 01:19 PM.
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  #2  
Old 07-12-2007, 11:07 PM
jsteele22 jsteele22 is offline
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bump .... any info appreciated

I think I've got it figured out, but can someone at least tell me which hose in the picture connects to the PCV valve ? Is it H415082 ? It sorta looks that way in the pic, but then again, it sorta doesn't.

Thx


Last edited by jsteele22; 07-12-2007 at 11:09 PM.
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  #3  
Old 07-13-2007, 03:58 AM
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dannmarr dannmarr is offline
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The diagram is tricky, but you are correct.

Last edited by dannmarr; 07-13-2007 at 05:05 AM.
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  #4  
Old 07-13-2007, 12:31 PM
jsteele22 jsteele22 is offline
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Quote:
Originally Posted by dannmarr
The diagram is tricky, but you are correct.

Great, thanks.

Yeah, actually if I stare at it long enough, I can now "see" that the hose is indeed bent at the end and points in the right direction. Somehow I missed that the first 23 times...

Our warm and fragile planet thanks you....
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  #5  
Old 07-25-2007, 02:22 PM
jsteele22 jsteele22 is offline
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Can someone help ? I'm still confused


I ordered new parts for the PCV system. In particular, the one I asked about before (11821, aka the "F" connector) is not a valve at all, simply a 3-way connector. So my big question is :

1) where does the top port of this F connector (hose H412172) go ?

I had thought that it went to the intake system, after the air filter but before the throttle plate. But this would create a substantial path for air to flow from the air filter through the "F" connector to the PCV valve, creating a huge vacuum leak/ high idle. No ?

Also, I've been reading up on PCV systems generally, and they all seem to have an inlet for fresh air that is distinct from the outlet to the PCV valve. My second question :

2) In our case, is the fresh air inlet via the breathers on the cylinder heads ? (If not, where is it ?)

Thanks,

Jeff
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  #6  
Old 07-26-2007, 10:44 AM
SVX33 SVX33 is offline
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Fresh Air

Quote:
Originally Posted by jsteele22
Can someone help ? I'm still confused


I ordered new parts for the PCV system. In particular, the one I asked about before (11821, aka the "F" connector) is not a valve at all, simply a 3-way connector. So my big question is :

1) where does the top port of this F connector (hose H412172) go ?

I had thought that it went to the intake system, after the air filter but before the throttle plate. But this would create a substantial path for air to flow from the air filter through the "F" connector to the PCV valve, creating a huge vacuum leak/ high idle. No ?

Also, I've been reading up on PCV systems generally, and they all seem to have an inlet for fresh air that is distinct from the outlet to the PCV valve. My second question :

2) In our case, is the fresh air inlet via the breathers on the cylinder heads ? (If not, where is it ?)

Thanks,

Jeff
Fortunately I just had all of that apart. The top connection on the F connects to the bottom of the intake hose before the throttlebody, or more precisely to the chamber at the throttlebody connection where all the oil from blowby collects.
John
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  #7  
Old 07-26-2007, 11:44 AM
jsteele22 jsteele22 is offline
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Quote:
Originally Posted by SVX33
Fortunately I just had all of that apart. The top connection on the F connects to the bottom of the intake hose before the throttlebody, or more precisely to the chamber at the throttlebody connection where all the oil from blowby collects.
John
Do you mean the place in this picture (at the right) where it says "Refer to figure 082A" ?



What's to keep air from flowing from there, through the "F" connector, and through the PCV valve, resulting in an absurdly high idle ? Is the PCV valve smart enough to only let air pass into the intake when the vacuum there is low ? I know that if I just blow through it (I got a new one) the air flows with almost no restriction.
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  #8  
Old 07-26-2007, 06:11 PM
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dannmarr dannmarr is offline
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Item #H512191 does not connect to the F connector. That is an piece that connectes on the left side of the diagram (refer to fig 082A) and continues to the right side of the diagram (refer to fig 082A).
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  #9  
Old 07-26-2007, 08:47 PM
jsteele22 jsteele22 is offline
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Can anybody show me where the top tube from the F connector does go ? From John's (SVX33) description, it sounded like it must be the one on the lower right of the picture (refer to fig 082A).

dannmarr's post says this port is used by hose H512191, but I must say that in the figure it looks like that hose is connected to two other ports (the other "refer to fig 082A" and the unlabeled one on the bottom of the round part of the tube.)

This is all pretty confusing because I don't have any of the parts forward of the throttle body itself, and also b/c I can't understand what the top port of the F connector is for. It seems to me that if fresh air is able to flow into the breathers on the cylinder heads and from there into the crankcase, then all that is needed is the lower F connector port to the PCV valve. But obviously, Subaru had a reason for that one extra tube......
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  #10  
Old 07-26-2007, 09:33 PM
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dannmarr dannmarr is offline
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I replaced the F connector with the hoses not long ago, I'll try to take some photos tomorrow for you.
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  #11  
Old 07-26-2007, 10:17 PM
jsteele22 jsteele22 is offline
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Quote:
Originally Posted by dannmarr
I replaced the F connector with the hoses not long ago, I'll try to take some photos tomorrow for you.

That would be awesome.

I actually have been reading up more on how the PCV valve works, and its a pretty amazing little gizmo, considering how simple it is. In particular, I finally understood why there is a connection to the intake and why this doesn't screw up the engine idle.


The PCV valve is not just a simple one-way check valve like I had imagined. In fact it only lets air through if there is a moderate difference in pressure : at zero difference or at high difference, it shuts off.

I checked this with a fresh PCV valve and a compressed air hose. As I began blowing from below (i.e., crankcase side) with my fingers forming a very loose seal, I could see the silver "pintle" inside the PCV valve raise up off the bottom seat and begin to let air through. As I increased the air flow, the pintle kept rising. At a fairly high flow, it hit its top seat, abrubtly sealing the passage shut again; this made the air seek another route and it squeaked audibly through my fingers.

So here's what the PCV valve does in practice :

At idle, the pressure difference is so high that the valve shuts off and does not let any air flow into the manifold. There's usually very little blowby at idle, but if there is any, it will flow from the crankcase to the air intake. While cruising, the pressure difference is more moderate, so the valve opens and some air flows from the crankcase (and the air intake) into the manifold. During a backfire, the pressure difference is in the wrong direction (and huge !) so the valve closes. At WOT, the manifold vacuum is nearly zero, so the valve tends to be "just" closed. If there is any blowby gas in the crankcase, this will open the valve. If there is a whole lot of blowby, this will close the valve again : this could be bad (pressurizing the crankcase), so that's why there is an additional line back to the air intake.

I feel a lot better now that I understand what all those hoses are about ! Hope somebody else finds this interesting !

p.s. After re-reading this, the only thing I'm still a little unsure of is the flow of fresh air into the crankcase. My hunch is that at cruising RPMs there is a flow of air from the air intake, through the breathers in the heads, to the crankcase, which is then pulled through the PCV valve by the manifold vacuum. Sounds good enough for me.

Last edited by jsteele22; 07-26-2007 at 10:24 PM.
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  #12  
Old 07-27-2007, 03:08 PM
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dannmarr dannmarr is offline
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The pictures did not come out but here is a quick drawing of the vacuum hose setup. Good luck.
Attached Images
File Type: jpg vacuum diagram.jpg (220.3 KB, 164 views)
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  #13  
Old 07-27-2007, 09:33 PM
jsteele22 jsteele22 is offline
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Quote:
Originally Posted by dannmarr
The pictures did not come out but here is a quick drawing of the vacuum hose setup. Good luck.

Cool. That's exactly what I was looking for.

Thanks.
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