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GDs gonna kill me


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14 replies to this topic

#1 hatchsub

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Posted 07 January 2010 - 11:07 AM

Yup...asking it again seeing as how i have oil everywhere from my pcv. I know how you hooked it up using that specialized hose that drops down to a 1/4" or thereabouts but i saw recently another post of yours saying you could just hook the passenger side directly into the air cleaner and hook the drivers side directly into the pcv? Would that be another acceptable way of doing it?

And before someone jumps down my throat...i did do a search...just couldnt find it:rolleyes:

#2 GeneralDisorder

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Posted 07 January 2010 - 12:21 PM

You need that 1/4" vacuum breaker line to prevent the PCV from sucking oil out of the driver's side head. You can build an adaptor from inexpensive brass fittings at home depot. About $20 will do it. You come off the driver's side head to a standard Subaru plastic T fitting, then one T goes to the PCV valve while the other reduces to 1/4" and goes to the filter.

I might have said that if you *didn't* need the vacuum breaker you could just run from the head to the PCV...... but I don't remember. I would have to see the post to figure out what I meant if I said that.

GD

#3 hatchsub

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Posted 07 January 2010 - 12:54 PM

Ok thanks GD. I gotcha but just one more question...it seems like the hose that goes to the PCV doesnt reduce down to 1/4 inch and stays big? How is that going to help my oil sucking problems. If i understood it stays big but the hose going to the breather (air cleaner) reduces. Or is it the air cleaner that is sucking the oil to the pcv valve and the 1/4 reducer keeps it from doing that?

Edited by hatchsub, 07 January 2010 - 12:57 PM.


#4 '84 Flat-Four

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Posted 07 January 2010 - 01:37 PM

This may help, I know it helped me out... Don't know where I found them on here but I had them saved on my computer... Thanks to GD for these pics...

Attached Files



#5 GeneralDisorder

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Posted 07 January 2010 - 01:54 PM

The 1/4" line is just there to prevent full manifold vacuum from being present in the line from the PCV valve to the head. It's like drilling a hole in the side of the hose for your vacuum cleaner - it's not going to suck as hard with the hole there as it did before you drilled the hole. Make sense now? The size of the hole is known as the "orifice" size and the size dictates how much vacuum will reach the head and thus how much flow the PCV system will get. The size is somewhat important - it needs to be close to the size of the stock hose that Subaru used to maintain the correct PCV flow characteristics. Thus the 1/4" ID as that is very close to the original hose size (it's probably 6mm ID).

GD

#6 GeneralDisorder

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Posted 07 January 2010 - 02:06 PM

I need you to undertand this so you can explain it to people. I'm sick of being the only one around here that knows how to setup a PCV system on an EA. :lol:.

It's one thing to copy what I've done and just trust that I know what I'm talking about - it's another to understand it and be able to explain how and why it works. Frankly I didn't understand it either till I spent the last few years working on vacuum pumps and systems every day. Vacuum is a strange beast and there's a whole learning curve surrounding it that most people are not at all familair with. Especially high-vac applications where you get down to the micron or millimicron range. :rolleyes:

GD

#7 hatchsub

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Posted 07 January 2010 - 02:41 PM

Got it. Now to get some supplies to fix mine.

#8 mountaingoatgruff

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Posted 07 January 2010 - 07:19 PM

hey guys thanks for bringing this up.

i unintentionally eliminated that vac relief line when i did my SPFI swap but after reading this thread and checking with my '84 FSM i think i'll fix that.

#9 hatchsub

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Posted 07 January 2010 - 07:47 PM

I need you to undertand this so you can explain it to people. I'm sick of being the only one around here that knows how to setup a PCV system on an EA. :lol:.


GD


Crap. Now i understand it. Im screwed. :lol: A portion of your burden has been lifted lol.

#10 GeneralDisorder

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Posted 07 January 2010 - 08:02 PM

i unintentionally eliminated that vac relief line when i did my SPFI swap but after reading this thread and checking with my '84 FSM i think i'll fix that.


The SPFI uses a similar system but there were two different setups used for the SPFI. The system used till like '91 or thereabouts uses a smaller ID line like the carb models - after that they made a change to prevent oil burning on long, sweeping, right hand turns - this involved (near as I can tell) eliminating the smaller ID line - which I suspect sacrifices PCV system effeciency in the intrest of not having huge clouds of oil smoke after long right hand turns. They didn't have much choice considering the problem they were faced with solving - at least not without making a big $$$ change to all the SPFI cars built prior to the recall - the fix was cheap and doesn't seem to have caused longevity issues that this board has noted.

One thing to watch out for with the SPFI - the PCV air is still metered - it goes through the MAF and as such you CANNOT have a leak in the PCV system as it will result in a large vacuum leak as far as the fuel trim is concerned. Same goes for the whole crankcase - dipstick o-ring, etc. All of the air in the crankcase is metered so it has to remain a closed system entirely behind the MAF sensor.

GD

#11 GeneralDisorder

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Posted 07 January 2010 - 08:05 PM

Crap. Now i understand it. Im screwed. :lol: A portion of your burden has been lifted lol.


Thank you! Next time this question arises - you run with it. A performance evaluation will follow :grin:

GD

#12 eulogious

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Posted 08 January 2010 - 02:11 AM

The SPFI uses a similar system but there were two different setups used for the SPFI. The system used till like '91 or thereabouts uses a smaller ID line like the carb models - after that they made a change to prevent oil burning on long, sweeping, right hand turns - this involved (near as I can tell) eliminating the smaller ID line - which I suspect sacrifices PCV system effeciency in the intrest of not having huge clouds of oil smoke after long right hand turns. They didn't have much choice considering the problem they were faced with solving - at least not without making a big $$$ change to all the SPFI cars built prior to the recall - the fix was cheap and doesn't seem to have caused longevity issues that this board has noted.

One thing to watch out for with the SPFI - the PCV air is still metered - it goes through the MAF and as such you CANNOT have a leak in the PCV system as it will result in a large vacuum leak as far as the fuel trim is concerned. Same goes for the whole crankcase - dipstick o-ring, etc. All of the air in the crankcase is metered so it has to remain a closed system entirely behind the MAF sensor.

GD


Does this apply to the MPFI/turbo's as well? I have a 1990 turbo loyale and was wondering if the same principals applied to that as well because I get the smoke on the long right hand turns, but since it's a turbo I didn't know if it applied or not, since the turbo introduces positive pressure to the system... but my thinking could be off on this as well.

Thanks for explaining it better, now I understand how the system works and why it was "flawed", now I just need clarification on my damn turbo :rolleyes: Thanks GD!

#13 mountaingoatgruff

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Posted 08 January 2010 - 03:45 AM

The SPFI uses a similar system but there were two different setups used for the SPFI. The system used till like '91 or thereabouts uses a smaller ID line like the carb models - after that they made a change to prevent oil burning on long, sweeping, right hand turns - this involved (near as I can tell) eliminating the smaller ID line - which I suspect sacrifices PCV system effeciency in the intrest of not having huge clouds of oil smoke after long right hand turns. They didn't have much choice considering the problem they were faced with solving - at least not without making a big $$$ change to all the SPFI cars built prior to the recall - the fix was cheap and doesn't seem to have caused longevity issues that this board has noted.

One thing to watch out for with the SPFI - the PCV air is still metered - it goes through the MAF and as such you CANNOT have a leak in the PCV system as it will result in a large vacuum leak as far as the fuel trim is concerned. Same goes for the whole crankcase - dipstick o-ring, etc. All of the air in the crankcase is metered so it has to remain a closed system entirely behind the MAF sensor.

GD


is oil burning during rh turns a problem with SPFI EA82's? i put almost 10k on my hatch after SPFI and never noticed any huge clouds of smoke from my car but then its not ohc.

so if the crankcase air is metered would it be practical to search for a vac leak around the oil filler & dipstick? assuming the vac leak couldn't be found elsewhere, of course.

#14 Gloyale

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Posted 09 January 2010 - 11:52 AM

Number one thing I've done to prevent Oil from being sucked up into the intake (from the passenger side head. ussually) is to put an actual clamp on all the PCV lines. (espescially turbos)

Even on non turbos, when you get that PCV hose clamped down tight, it can actually pull enough vaccuum through it to suck gases out of the case.

When the PCV connection is loose......the suction of air rushing into the aircleaner overwhelms the suction of the PCV, and oil and crank gases get sucked up into the aircleaner. Keep that clamped tight, and the gases will be drawn into the intake by the PCV (below the carb, insead of above it soaking your airfilter)

#15 GeneralDisorder

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Posted 09 January 2010 - 09:30 PM

Oil burning on long, sweeping, RH turns was a problem with the pre-Loyale SPFI system's. It was addressed by a "kit" that was to be installed if the customer complained about it. Later in the early 90's the "kit" became standard on Loyale's.

I've had it happen with a few older SPFI's that I've owned. My SPFI converted Brat has the SPFI system from a '93 Loyale so it's never done it. But I see no reason why the EA81 wouldn't be prone to the same problem given the way the early design was setup.

GD




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