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Old 04-14-2004, 08:53 PM   #1
White 2.5rs
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Default pcv venting, the real way to do it?

i wanna set all my pcv crap up, i talked to kaos a little about it and he said he wasnt for sure,so do i just run the 2 valve cover ones, and the 2 block ones into the can and put a breather on the other side? or should i run it back into the intake?

thanks
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Old 04-14-2004, 09:07 PM   #2
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Quote:
Originally posted by White 2.5rs
i wanna set all my pcv crap up, i talked to kaos a little about it and he said he wasnt for sure,so do i just run the 2 valve cover ones, and the 2 block ones into the can and put a breather on the other side? or should i run it back into the intake?

thanks
the two valve covers, and both block ones into the can, the other hole in the can goes to the PCV valve(on the intake manifold)
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Old 04-14-2004, 09:12 PM   #3
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oh, roger, thanks
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Old 04-14-2004, 11:54 PM   #4
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I agree!!
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Old 04-15-2004, 08:58 AM   #5
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I disagree with you guys, the valve covers should both connect to a "vented" catch can (or if you want to be cheap, use two small valve cover breather filters). The block should be connected to a "sealed" catch can and then the catch can is to be connected to the manifold via the PCV valve.

**Notice, there are 2 types of catch cans here!**

You need to supply fresh air to the crankcase. You cannot just connect EVERYTHING to the intake manifold you know.
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Old 04-15-2004, 09:49 AM   #6
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isnt it setup like kaos said stock? i might be wrong id unno
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Old 04-15-2004, 01:34 PM   #7
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Actually you DO want to have ALL of the vents going to a vaccuum source. This is the way it came stock. You don't HAVE to, but I have heard people complain that they are getting hesitation, and oil consumption from just venting to the atmosphere. All you need is a catch can. There is a thread on here started be imprezarsx that has a an awesome explanation of this. He said that he had problems until he set up his pcv correct.
http://forums.nasioc.com/forums/show...hreadid=497603
here is the link.
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Old 04-15-2004, 02:29 PM   #8
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If you are reffering to this setup, good luck to you. It is wrong. You NEED to have a source for fresh air when the PCV valve on the intake manifold is drawing a vacuum on the crankcase, doesn't matter if you take it from the turbo to air filter pipe or from the atmosphere. On boost, your crankcase will be pressurized a slight bit (normal), this pressure can be evacuated through the valve cover breathers to the turbo inlet pipe (which provides a slight vacuum) or to a vented catch can (no vacuum but good enough because you have a positive flow out of the valve covers).....Anyway, that is all I have to say, you can set yours up however way you like....I hope you don't do it like the diagram below.
Quote:
Originally posted by ImprezaRSX
This is what I believe an ideal setup should look like.

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Old 04-15-2004, 02:37 PM   #9
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Quote:
Originally posted by Boostup!
If you are reffering to this setup, good luck to you. It is wrong. You NEED to have a source for fresh air when the PCV valve on the intake manifold is drawing a vacuum on the crankcase, doesn't matter if you take it from the turbo to air filter pipe or from the atmosphere. On boost, your crankcase will be pressurized a slight bit (normal), this pressure can be evacuated through the valve cover breathers to the turbo inlet pipe (which provides a slight vacuum) or to a vented catch can (no vacuum but good enough because you have a positive flow out of the valve covers).....Anyway, that is all I have to say, you can set yours up however way you like....I hope you don't do it like the diagram below.
I'm not quite clear on what you are saying here about venting what parts to where... could you draw up a drawing? I think the other guys would appreciate it too.

Here's another question that might clear things up: Are the valve cover breathers directly connected to the crank-case interal to the head/block? This was never clear to me and I haven't gotten a chance yet to examine an engine for that purpose.

-Charlie
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Old 04-15-2004, 03:03 PM   #10
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Charlie, you are absolutely correct! The valve covers are connected to the crankcase, they all share the same air. If the crankcase is pressurized, the valve covers will be pressurized too and vice versa for vacuum. I think you get the idea now....no need for a drawing?
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Old 04-15-2004, 03:20 PM   #11
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mmm been running mine with valve covers T's with Block breather to the vented catch can and then the PCV capped...

I remember this was how Jan shim had it...
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Old 04-18-2004, 12:57 AM   #12
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Would you please explain to me why on earth you would need fresh air?

Venting anything to atmosphere lowers the amount of vacuum placed on the crankcase and it increases the volume of airflow THROUGH the crankcase which WILL INCREASE oil consumption because the air will pull all the oil vapor with it into your motor.

So please, don't use my drawing saying it is wrong.
Because, it isn't.

My design has overpressure protection and a constant vacuum source. You WONT pressurize your crankcase with that design. Unless of course you have excessive blowbye from an extremely worn out engine. If that's the case, nothing will help.
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Old 04-18-2004, 01:04 AM   #13
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At idle, manifold vacuum is applied to the catchcan and loads. This vacuum will want to suck air in through the turbo inlet pipe. However the check valve will seat and prevent this. This will place a strong vacuum on the crankcase. In the event of excessive blowbye or crankcase pressure, the previously discussed check valve will unseat, releaving any pressure to the turbo inlet. This protects the crankcase from excessive pressures.

Under boost the intake manifold is pressurized and the turbo inlet has vacuum (from sucking air into the engine). The intake manifold check valve will seat preventing any pressure from getting into the crankcase. Any blowbye will be removed by the vacuum source at the turbo inlet.
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Old 04-18-2004, 02:31 AM   #14
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ImprezaRSX, on my downpipe i have two o2 sensors, i only need one, what im planning on doing is run my crankcase vent and valve cover vents teed to a catch can and then routed to my downpipe for vacuum. do you see anything wrong with this setup? also, am i wrong to say that i can eliminate my pvc pipe all together.


i might also put my boost gauge on the line at first just to see what kind of vacuum this produces.



thanx, jay
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Old 04-18-2004, 04:32 AM   #15
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I had the exact same set up as Imprezarsx but after a few months of driving, I noticed some foamy sludge build up underneath my oilcap,on my dipstick, and water in the catchcan. Since then, I have returned my pcv setup back to stock and have my catchcan hooked up between the crankcase vent and pcv valve. So far, the problems has disappeared for 3 months. I've read that a pcv system has a clean side(valvecover vents) and a dirty side(crankcase vent). Hooking these two together will mess things up.
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Old 04-18-2004, 10:49 AM   #16
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Quote:
Originally posted by Turbotegra
I had the exact same set up as Imprezarsx but after a few months of driving, I noticed some foamy sludge build up underneath my oilcap,on my dipstick, and water in the catchcan. Since then, I have returned my pcv setup back to stock and have my catchcan hooked up between the crankcase vent and pcv valve. So far, the problems has disappeared for 3 months. I've read that a pcv system has a clean side(valvecover vents) and a dirty side(crankcase vent). Hooking these two together will mess things up.

That's very interesting. You obviously had water coming from somewhere. Maybe excessive condensation.... I've had zero problems over the last 6 months. Are you sure you added an extra check valve in the turbo inlet? that's something you have to do on your own.

I have zero experience with routing pcv to the exhaust. I honestly don't completely understand that one. If the exhaust was a source of vacuum air would go in, not out of it. When people talk about scavenging effect, it's a relative term. Moving a volume of air/fluid through a pipe WILL have headloss. And headloss is pressure....
I would be very interested to see what kind of vacuum that produces. I would recommend hooking up a gauge before actually running any connections to it.

The only way I can see that working is if you used an eductor. But this would require adding a nozzle to your exhaust system. Simply using an O2 sensor bung wouldn't work. This works just like an "air ejector" that we use on our power plants, but it would increase backpressure in the exhaust which would increase turbo lag.
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Old 04-18-2004, 10:53 AM   #17
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the yellow is the low pressure region that would have vacuum to pull air from the crankcase. The nozzle (notice the restriction) is where the exhaust gas would flow. The gas in that section is traveling at supersonic speeds. Also, if you had the other side of your pcv vented to atmosphere you would be suckin in a lot of outside air a most likely get tons of backfires and pops when decelerating or shifting.
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Old 04-18-2004, 10:54 AM   #18
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Old 04-18-2004, 01:53 PM   #19
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Now I'm lost more than ever!
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Old 04-18-2004, 02:10 PM   #20
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Quote:
Originally posted by Wedge
Now I'm lost more than ever!
Ditto for me.
-Tod
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Old 04-18-2004, 02:12 PM   #21
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Quote:
Originally posted by Turbotegra
I had the exact same set up as Imprezarsx but after a few months of driving, I noticed some foamy sludge build up underneath my oilcap,on my dipstick, and water in the catchcan. Since then, I have returned my pcv setup back to stock and have my catchcan hooked up between the crankcase vent and pcv valve. So far, the problems has disappeared for 3 months. I've read that a pcv system has a clean side(valvecover vents) and a dirty side(crankcase vent). Hooking these two together will mess things up.
I'm glad you found out early, Turbotegra. Pollution of the crankcase oil increases with increasing cylinder pressure. The by-products of gasoline and air combustion are primarily carbon monoxide, nitrous oxides (NOx) and unburned hydrocarbon by-products. Some of these products are forced around the piston rings and down into the crankcase; these are called blow-by products. These gases mix with the oil vapors in the crankcase will immediately begin to cook up some nasty substances that can, and will, harm your engine. That's the foamy sludge you found in your engine. If the crankcase is not adequately ventilated (read: ventilation requires fresh air, NOT just pulling a vacuum w/o replacing the air), the motor oil will quickly become contaminated and heavy sludge accumulations will begin to form. Internal parts, not protected by the motor oil, will begin to rust and/or corrode due to the water and acids that will become trapped within the crankcase.

For others reading this, please do a search on google (or your fav search engine) for PCV and fresh air. Read only from reputable sources. I think you'll find more useful information there then relying on what's being said here. There is a lot more info about how important a PROPERLY setup/maintained PCV system is that you should read about.
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Old 04-18-2004, 06:09 PM   #22
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I have mine setup like this picture shows.... WITHOUT THE BLUE
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Old 04-18-2004, 06:11 PM   #23
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where there's a little red "a" is where there is a breather hole. Im going to try and plug that, and run a T into the line that goes to the PCV, and have it run to the intake with a check valve,
Most likely the T will be closer to the PCV itself, but this is just for illustration purposes.
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Old 04-18-2004, 09:31 PM   #24
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What is the black line connecting in that picture?
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Old 04-18-2004, 11:38 PM   #25
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very good info/debate
take it easy, Micah
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