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PCV system questions


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34 replies to this topic

#1 hatchsub

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Posted 25 May 2009 - 08:21 PM

Im pretty sure that my PCV system is responsible for my blue smoke sometimes. I have a weber carb and therefore have my pcv set up like this; Both valve covers are connected by a hose. There is a t-fitting that goes down to the pcv. Off of that line there is another T-fitting that shoots up to the weber air cleaner. Would it do any harm and would it help if i just put mini breathers on both valve covers and left the PCV going straight up to the air cleaner?

#2 GeneralDisorder

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Posted 25 May 2009 - 11:09 PM

It would do a lot of harm - but not much *more* harm than your current system which is not doing the job either.

The goal is to remove blow-by gasses from the crankcase - in the old days this was done with a road draft tube, but that became unacceptable with the environmental movement.

The PCV system needs a directional flow - in one head and out the other then to the PCV valve. But you need a smaller diameter hose between the second head and the PCV valve going back to the air filter in order to break the high vacuum and prevent oil being sucked into the manifold.

GD

#3 Loyale 2.7 Turbo

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Posted 26 May 2009 - 03:02 AM

Im pretty sure that my PCV system is responsible for my blue smoke sometimes ...


I Have some Pictures about that Setup and how I did Fix that, in my "Weber Swap" Writeup... if you want to see `em and How I Fixed that, Just Click on my Avatar and you`ll Reach a List of my Writeups.

Kind Regards.

#4 Spiffy

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Posted 26 May 2009 - 03:48 PM

I have the same setup as you and haven't had any blue smoke...

I took the 2 stock hoses that went to the subaru air filter and hooked them to the weber air filter... the driver's side already had the pcv line hooked into it... I simply made a T from pipe fittings at home depot and hooked them into the supplied weber air filter spot...

since this is the same setup as stock I don't understand how it could be wrong... the stock system had both valve cover hoses going to the air cleaner, one on each side...

maybe mine is ok because of the different diameter hoses... no idea...

#5 GeneralDisorder

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Posted 26 May 2009 - 09:30 PM

since this is the same setup as stock I don't understand how it could be wrong... the stock system had both valve cover hoses going to the air cleaner, one on each side...

maybe mine is ok because of the different diameter hoses... no idea...


It is not the same as stock if you don't have the exact same diameter hoses as stock. When you are talking about flow rates and directions, hose diameter plays a huge role. Often in vacuum systems you have to carefully "tune" the system by use of very accurate "orifices" that are inserted to restrict flow rates at certain points. I have explained how the system works in other threads and it's tireing to do it over and over. Do a search for "PCV" and my user name and I'm sure you'll find it.

GD

#6 Spiffy

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Posted 27 May 2009 - 11:29 AM

It is not the same as stock if you don't have the exact same diameter hoses as stock. When you are talking about flow rates and directions, hose diameter plays a huge role.


that makes sense... and I did reduce the 5/8 and 5/16 hoses into a single 1/2 so that's got to be messing up the flow a bit... I guess the best thing to do would be to have 2 holes in the weber air filter the same size as the stock hoses and get rid of the reduction T...

time for another trip to home depot... hehe...

#7 Flowmastered87GL

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Posted 27 May 2009 - 06:10 PM

I ran just bulk hose on my GL... never smoked :)

I had a genuine subaru PCV valve also.... do you have one or just a fram cheap-o???

#8 GeneralDisorder

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Posted 27 May 2009 - 07:32 PM

that makes sense... and I did reduce the 5/8 and 5/16 hoses into a single 1/2 so that's got to be messing up the flow a bit... I guess the best thing to do would be to have 2 holes in the weber air filter the same size as the stock hoses and get rid of the reduction T...


That is not the way the system works. You need ONE port on the filter. From there you T into two 5/8" hoses - one goes to the passenger side head. The other reduces to 1/4" ID then back to 5/8" and T's into the line from the drivers side head to the PCV valve. The key to making it work is the reduction to 1/4" ID to give an orificed vacuum break on the PCV line. Otherwise it will have too much suction and will pull oil out of the driver's side head.

GD

#9 hatchsub

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Posted 29 May 2009 - 08:56 AM

That is not the way the system works. You need ONE port on the filter. From there you T into two 5/8" hoses - one goes to the passenger side head. The other reduces to 1/4" ID then back to 5/8" and T's into the line from the drivers side head to the PCV valve. The key to making it work is the reduction to 1/4" ID to give an orificed vacuum break on the PCV line. Otherwise it will have too much suction and will pull oil out of the driver's side head.

GD


Im trying to picture that. Do you happen to have a picture of that setup?

Also to answer the other question im running a genuine subaru pcv valve.

#10 GeneralDisorder

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Posted 29 May 2009 - 03:27 PM

Ok - I got you pictures - so all you people that are running your PCV wrong GO FIX IT! I'm tired of trying to explain it anyhow...

Overview of the system:
Posted Image

This shows the "special" EA71 (gen 1, round air filter type) hose and special T fitting that makes this setup easy and clean - if you can find one. I suppose there are part numbers associated with them and you could order a set - I don't have any extra so don't ask! The blue T-fitting from the filter is from an EA82 SPFI. Hey look..... I guess I do recycle!

Posted Image

And here's another angle:

Posted Image

Re-read my last post and then look at these pictures. I'm sure it will make sense to you if you stare at it for a while.

Any questions?

GD

#11 Dirk

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Posted 26 February 2010 - 09:37 PM

Hey,

The search system won't let me search for PCV. How do I get around this?

#12 hatchsub

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Posted 26 February 2010 - 10:09 PM

Im not sure but i usually get around it by searching for something else like

-hose routing
-vacuum
-weber breather

typing vacuum in got me this thread again. I kno there is probably a way around the search feature but i havent figure it out or if it was said i forgot.

#13 Dirk

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Posted 26 February 2010 - 10:30 PM

Sweet. Thanks.

This is the system that my car came with. It appears to be far more simple than the systems being talked about here. I wonder what the draw backs are of this simpler system. Will it clog the carb?

Posted Image

#14 Dirk

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Posted 26 February 2010 - 10:44 PM

This is the "system" I am currently using. This is actually legal in New Zealand! So much for being a 'green' country!

Posted Image

#15 GeneralDisorder

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Posted 26 February 2010 - 11:12 PM

The drawback is that you don't have a PCV valve in the manifold so any oil that gets sucked into the system ends up in the carb and air filter instead. Plus it's probably not as effective for removing crankcase gasses since the two pipes are fighting each other and trying to suck on both sides of the engine. With the PCV setup as talked about in this thread you have an IN and an OUT side of the engine creating a positive flow from one side to the other.

With the hose going into the soda can you have NO flow - so that's completely innefective. You might as well just leave the valve cover port open......

GD

#16 WRX2FFU

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Posted 26 February 2010 - 11:37 PM

Kinda un related but.... Unless your pulling oil into the carb your blue smoke is most likley ring issues.

#17 GeneralDisorder

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Posted 26 February 2010 - 11:47 PM

Kinda un related but.... Unless your pulling oil into the carb your blue smoke is most likley ring issues.


Probably not - valve stem seals is much more likely on Subaru's.

GD

#18 Dirk

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Posted 26 February 2010 - 11:47 PM

With the hose going into the soda can you have NO flow - so that's completely innefective. You might as well just leave the valve cover port open......

GD


Aye, I know that. The cans are just catching the crap that comes out of the hoses.

The stock air filter box was always a bit gunky. Think I might salvage a PCV system from a wreck and bang in on.

#19 Dirk

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Posted 27 February 2010 - 12:19 AM

Just been looking it up. I guess I'm gona have to replace the whole manifold then.

#20 GeneralDisorder

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Posted 27 February 2010 - 02:02 AM

Why not just drill and tap your existing manifold or adapt a PCV valve that's designed to go inline with the hose and simply T it into the brake booster?

GD

#21 Dirk

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Posted 27 February 2010 - 02:19 AM

Errr. Cool. thats what I'll do. Thanks man.

#22 eulogious

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Posted 27 February 2010 - 03:58 AM

Hey,

The search system won't let me search for PCV. How do I get around this?


The easiest way I found is using a '*' at the end of the word, so to search for 'PVC' you would search for 'PVC*' This has always worked for me! Just thought I would throw that tip in there...

#23 spikedbeetle

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Posted 27 February 2010 - 09:33 AM

Would it do any harm and would it help if i just put mini breathers on both valve covers and left the PCV going straight up to the air cleaner?


This is almost exactly what I did. I put two mini breathers on and got rid of the PCV all together.

It would do a lot of harm. GD


I do have an air cleaner base that I am currently not using for one of my carbs on my dual carb setup that has a line for a crank case breather. Do you think it work work well if I left a mini breather on one valve cover and ran a line from the other valve cover through an inline PCV and then into the air cleaner? Would that create the through cross flow that the engine needs to work properly?

Here is how it sits now.
Posted Image

#24 Gloyale

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Posted 28 February 2010 - 12:17 PM

Do you think it work work well if I left a mini breather on one valve cover and ran a line from the other valve cover through an inline PCV and then into the air cleaner? Would that create the through cross flow that the engine needs to work properly?


ONe side "open" w/ breater.

Other side hooked into a PCV valve installed in Manifold, or "T''d into brake booster vac line.

Point being in the end.....the only reason the air filter box is part of the PCV....is to filter air before going into the one side breater.....if you have a seperate filter on there, then the other vavle cover port get's hooked straight to the valve. No further need to tie it into the air box.

#25 naru

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Posted 28 February 2010 - 01:02 PM

ONe side "open" w/ breater.

Other side hooked into a PCV valve installed in Manifold, or "T''d into brake booster vac line.

Point being in the end.....the only reason the air filter box is part of the PCV....is to filter air before going into the one side breater.....if you have a seperate filter on there, then the other vavle cover port get's hooked straight to the valve. No further need to tie it into the air box.


Not completely true.
At wide throttle openings(low manifold vacuum,high blowby),PCV is unable to handle the flow and blowby gases are routed to the carb intake.




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