# PCV Airflow Design



## 20AE-2306 (Jan 21, 2006)

I've been wondering about the 1.8T PCV system. It seems to me that it has about 3 vacuum sources all pulling on the same section of piping in between the valve cover and under the intake manifold. How is this supposed to move air?
I took apart all the valves cause I had extras and it seems that the intake manifold wins at idle and the smaller line on the TIP wins during boost, and since those two sources are strongest, the large flying saucer is the PCV "intake" even though it actually has vacuum during boost, just not as much as the smaller line.
I've been meaning to try it, but I assume that if you push air into the PCV port on the valve cover, it doesn't come out anywhere does it? is air able to flow from the head to the oil pan without going through the external PCV piping?
I'm trying to figure out how the air really circulates if there is only one connection to the head and one to the oil pan, i.e. there is no in and out port on each that would allow air to cycle through. I'm assuming this is because there is a cloud of oil in there that would just evacuate in that kind of a setup.
The conclusion to my questions, is how did the changes made in later 1.8T's help with the sludge problems that the original models had? I have simplified a few things here and there and it seems to run well but I want to make sure I'm not undoing the sludge fixes, etc.
The only change I made that I'm not totally sure about was to eliminate the PCV connection to the intake manifold at the brake/vacuum booster, this really helped with idle quality as I think it is difficult for the ECU to regulate manifold vacuum when there is a huge leak to the PCV system which is not a vacuum per-se. My idle vacuum went from 19-20 to 22hg's or so.
Still if there are some systems that rely on this that I'm not thinking of, I'd like to know. It seems that lots of people have made much more extreme changes to their PCV while simplifying their engine bay or adding a catch can..
Any info would be appreciated.


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## bekr83 (May 17, 2006)

*Re: PCV Airflow Design (20AE-2306)*

my head hurts


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## 01gtiaww (Jan 31, 2006)

*Re: PCV Airflow Design (bekr83)*

I have been running with only one source to the brake servo (brake booster) for a while now with no problems. All it needs to function is one strong source of vacuum. 
As for the rats nest of hoses, I simplified things with a catch can. I did not want to eliminate the vacuum source from under the manifold to the lower crancase breather so all I did was I bought a T. 3/8 middle port and 3/4 for the side ports. I connected a line from the middle port of the T into the nipple in the middle of the intake manifold with a one way check valve inbetween, then I ran 3/4 hose for the upper breather off the valve cover teed into the 3/4 hose from the lower cranck case breather into the in of the catch can. As for the out hose back into the intake from the catch can, I eliminated the flying saucer, diverter valve looking thing and just ran a straight hose from the out of the catch can into the intake. My catch can came with 3/4 barbs so everything is still the same size as the OEM system. 3/4 plumbing with both vacuum sources still connected. One vacuum source is for when in vacuum, the other is for when in boost. http://****************.com/smile/emthup.gif 
Here is how the PCV system flows air under boost and vacuum.
















I used a Tee like this to keep the vac source from under the manifold. I placed an inline one way checkvalve with the flow towards the intake manifold.








Then I connected to the catch can from the differant location as shown below.
















And here you can see my one source of vacuum for the brake booster.








ANd this is the catch can i used with 3/4 oem like barbs made for Porsche 951 turbo applications.









_Modified by 01gtiaww at 1:07 PM 9-23-2007_

_Modified by 01gtiaww at 1:10 PM 9-23-2007_

_Modified by 01gtiaww at 1:23 PM 9-23-2007_


_Modified by 01gtiaww at 1:24 PM 9-23-2007_


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## Yareka (Mar 5, 2002)

*Re: PCV Airflow Design (20AE-2306)*

The op has a good idea of whats going on with his pcv system. The question you had about recirculating air in the crankcase and the valve cover shouldnt be needed because the pressure builds and is going to evacuate from the one open port since you have *positive* crankcase ventilation.
I simplified my system a little more than you guys did by only relying on boost in the inlet pipe to pull vacuum on the system. The 1/2" port on the intake mani feeds the brake booster. All smaller ports below the manifold feed the dv/fpr/boost guage/meth controller. Crankcase hose t's into the valve cover hose and goes into one side of the catch and the other line goes to the inlet. This way, theres no chance of ever pressurizing the crankcase with a busted or stuck check valve. My catch can fills up quicker(mostly moisture) than most since vacuum from the intake mani isnt pulling on it but I empty it every time I fill up my gas tank which is usually once a week.


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## one swell foop (May 7, 2006)

Where did you get that catch can? While messing around with and replacing vac lines, specifically the ones we are talking about here, and seeing the oil in my system, I've been thinking about adding a catch can to my system. Is this really necessary as my only real majot mod thus far is the APR chip, along with a TIP and K&N panel filter, and a DV valve.


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## 01gtiaww (Jan 31, 2006)

*Re: (one swell foop)*


_Quote, originally posted by *one swell foop* »_Where did you get that catch can? While messing around with and replacing vac lines, specifically the ones we are talking about here, and seeing the oil in my system, I've been thinking about adding a catch can to my system. Is this really necessary as my only real majot mod thus far is the APR chip, along with a TIP and K&N panel filter, and a DV valve. 


http://www.saikoumichi.com/ it's not cheap. Most people get them on ebay, but this is the only one that I have found that is 3/4 barb. And it's better to do it now than later, bacause eventually you will need it. http://****************.com/smile/emthup.gif


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## 20AE-2306 (Jan 21, 2006)

*Re: PCV Airflow Design (Yareka)*


_Quote, originally posted by *Yareka* »_The op has a good idea of whats going on with his pcv system. The question you had about recirculating air in the crankcase and the valve cover shouldnt be needed because the pressure builds and is going to evacuate from the one open port since you have *positive* crankcase ventilation.

Yeah I always forget to this about what the words *mean*, which sometimes better explain what the item does than casual observations which generally only provide partial conclusions.









_Quote, originally posted by *Yareka* »_I simplified my system a little more than you guys did by only relying on boost in the inlet pipe to pull vacuum on the system. The 1/2" port on the intake mani feeds the brake booster. All smaller ports below the manifold feed the dv/fpr/boost guage/meth controller. Crankcase hose t's into the valve cover hose and goes into one side of the catch and the other line goes to the inlet. This way, theres no chance of ever pressurizing the crankcase with a busted or stuck check valve. My catch can fills up quicker(mostly moisture) than most since vacuum from the intake mani isnt pulling on it but I empty it every time I fill up my gas tank which is usually once a week. 

Yeah that's exactly what I did except I kept the flying saucer until I get a catch can and I have two connections going to the TIP. Instead of a T, the Audi TT225 ha a nice hose that tee's off the valve cover for you , looks more stock. I would still keep the flying saucer if I got a catch can, I'd put the can after the saucer. Inside the saucer is a sort of diaphram check valve that activates at a certain point.
The one question I have about your setup is, does the motor generate positive pressure by itself? I know the motion of the pistons moving up and down creates pressure, but it is just from air slipping past the rings or something, acts like a bycycle pump? How else does the air get in there? Or, does it pump it from the head and push it out the crankcase below the intake mani?
BTW, that catch can above looks very much like an oil filter with two pipes welded on, I think maybe I'll do that!. I mean some oil filters let you drop the "can" part out, which would be ideal for empying it, and best of all: it's an oil filter, it's already setup to filter oil... http://****************.com/smile/emthup.gif 
Just an idea, might be worth a shot. Have to find the right one, it has to have a different top than our oil filters do, or if it does have that top then it would require some modification.










_Modified by 20AE-2306 at 4:03 PM 9-23-2007_


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## one swell foop (May 7, 2006)

*Re: PCV Airflow Design (Yareka)*

I simplified my system a little more than you guys did by only relying on boost in the inlet pipe to pull vacuum on the system. The 1/2" port on the intake mani feeds the brake booster. All smaller ports below the manifold feed the dv/fpr/boost guage/meth controller. Crankcase hose t's into the valve cover hose and goes into one side of the catch and the other line goes to the inlet. This way, theres no chance of ever pressurizing the crankcase with a busted or stuck check valve. My catch can fills up quicker(mostly moisture) than most since vacuum from the intake mani isnt pulling on it but I empty it every time I fill up my gas tank which is usually once a week. [/QUOTE]
Can you post a diagram of this, or pics? I'm still getting to know the system. Also, the hose coming off the bottom of the stock T that goes into the brake booster is cracked on my car. It wants to fall off as the crack is right at the T. I've zip tied it on as a temp fix. VW wants like $50 for this hose. I've recently replaced other vac lines, including the one to the stock oil catch disc as per this http://forums.vwvortex.com/zerothread?id=3458106 thread. Any tips on tubing to use? I'm currently using 3/4" heater tubing. Looked around the internet for reasonably priced silicon tubing in that size and was blown away by the ridiculous prices, even for black, which is the color I want.
I'm about to order that same saikou pictured above as the quality looks top notch.


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## Yareka (Mar 5, 2002)

*Re: PCV Airflow Design (20AE-2306)*


_Quote, originally posted by *20AE-2306* »_
Yeah I always forget to this about what the words *mean*, which sometimes better explain what the item does than casual observations which generally only provide partial conclusions.


























_Quote »_
I would still keep the flying saucer if I got a catch can, I'd put the can after the saucer. Inside the saucer is a sort of diaphram check valve that activates at a certain point.

The saucer is just an accumulator, to help turn the vapors into liquid so it can run back down to the crankcase instead of building up in the inlet. Problem is that it sucks at its job and it needs to go. The check valve probably just closes under vacuum so that the inlet/pcv doesnt fight itself going from vacuum into boost. maybe?

_Quote »_
The one question I have about your setup is, does the motor generate positive pressure by itself? 


The combustion process creates pressure/bypass even at idle, simply pull off the hose that goes into your catch can and you can smell it right away. Whats strange is that the early 1.8t valve covers didnt vent at all.


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## 01gtiaww (Jan 31, 2006)

*Re: PCV Airflow Design (one swell foop)*


_Quote, originally posted by *one swell foop* »_I simplified my system a little more than you guys did by only relying on boost in the inlet pipe to pull vacuum on the system. The 1/2" port on the intake mani feeds the brake booster. All smaller ports below the manifold feed the dv/fpr/boost guage/meth controller. Crankcase hose t's into the valve cover hose and goes into one side of the catch and the other line goes to the inlet. This way, theres no chance of ever pressurizing the crankcase with a busted or stuck check valve. My catch can fills up quicker(mostly moisture) than most since vacuum from the intake mani isnt pulling on it but I empty it every time I fill up my gas tank which is usually once a week. Can you post a diagram of this, or pics? I'm still getting to know the system. Also, the hose coming off the bottom of the stock T that goes into the brake booster is cracked on my car. It wants to fall off as the crack is right at the T. I've zip tied it on as a temp fix. VW wants like $50 for this hose. I've recently replaced other vac lines, including the one to the stock oil catch disc as per this http://forums.vwvortex.com/zerothread?id=3458106 thread. Any tips on tubing to use? I'm currently using 3/4" heater tubing. Looked around the internet for reasonably priced silicon tubing in that size and was blown away by the ridiculous prices, even for black, which is the color I want.
I'm about to order that same saikou pictured above as the quality looks top notch.


3/4 heater hose is just fine. I was also looking into the 3/4 silicone hose but is way to expensive for me. I get 5 feet of good quality 3/4 inch heater hose for $5 so I will stick to that. http://****************.com/smile/emthup.gif And yes the Saikou Michi OCC is a top quality design. This OCC is very well known in the EVO and Porsche world. http://****************.com/smile/emthup.gif It's a litttle expensive, but I don't mind spending the money.


_Modified by 01gtiaww at 8:52 AM 9-24-2007_


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## r0nd3L (Nov 1, 2005)

Looks like there are different views on this.
Some people just dump all the vacuum from intake manifold and just use inlet pipe as vacuum under boost.
Meanwhile, others suggest keeping one vacuum source from the manifold so there is still vacuum in the PCV system when car isn't boosting.
Now, which is the correct way to go? I really like the idea of using just one inlet pipe source for cleaner looks, but maybe that's harmful?
Also, the saucer thing seems to close when car gets into boost so it doesn't draw air from PCV system, is that right? I think that's beneficial to keep it, no?


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## 01gtiaww (Jan 31, 2006)

*Re: (r0nd3L)*

I try to keep the system as close to stock as possible, hence why I chose to keep both vacuum sources. Still pretty clean under the manifold. I eliminated everything and just added a 3/4 inch Tee with a 3/8 port in the middle like pictured above. The DV looking thing on the intake, serves as a mini catch can according to my research on the tex. It's not very functional at all. If you think about it all the oil enters the intake via that lil saucer so obviously it aint shut under boost. I just eliminated it as have most here. If you look at my diagrams posted above you can see that under boost all the air from both breather points get dumped into the intake through the saucer, so it is not closed under boost. http://****************.com/smile/emthup.gif 


_Modified by 01gtiaww at 2:10 PM 9-24-2007_


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## CapeGLS (Aug 3, 2002)

*Re: (01gtiaww)*

Nice thread! http://****************.com/smile/emthup.gif


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## one swell foop (May 7, 2006)

So once I have a catch can on, there is no need to even run a line to the spot on the TIP where the saucer resides? Just plug the hole? What did you guys who have done this use to plug the hole?


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## r0nd3L (Nov 1, 2005)

*Re: (one swell foop)*


_Quote, originally posted by *one swell foop* »_So once I have a catch can on, there is no need to even run a line to the spot on the TIP where the saucer resides? Just plug the hole? What did you guys who have done this use to plug the hole?

Only if you have vented catch can (they usually have a filter on the top). If it's not vented, you should just run it back into the TIP.


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## 01gtiaww (Jan 31, 2006)

*Re: (one swell foop)*


_Quote, originally posted by *one swell foop* »_So once I have a catch can on, there is no need to even run a line to the spot on the TIP where the saucer resides? Just plug the hole? What did you guys who have done this use to plug the hole?

You should always vent it back to the intake, unless the catch can you buy has a breather on top. Eliminate the saucer, get your self a little brass tube that fits into the hole where the saucer is and over the 3/4 inch hose and you should be good to go. Having a closed loop system is the best way to go in my opinion. Others may differ. http://****************.com/smile/emthup.gif


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## 20AE-2306 (Jan 21, 2006)

*Re: (r0nd3L)*


_Quote, originally posted by *r0nd3L* »_Also, the saucer thing seems to close when car gets into boost so it doesn't draw air from PCV system, is that right? I think that's beneficial to keep it, no?

I think what it does is to keep the higher amount of vacuum during boosting from pulling too much oil into the TIP. I actually opened up my saucer and cut the spring down to see what it would do. So I guess it's closing at lower boost pressures now, which seems fine, hopefully a little less oil.
As far as people who got rid of the vacuum booster and just connected the brake booster directly to the intake manifold - I also did this, but I think the brake booster works a little better with the stock configuration, it definitely can't be better this way. I think vacuum from the TIP activates the brake booster while you are boosting which otherwise wouldn't happen so if you needed to brake hard immediately after boosting, it might not work so well.


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## 01gtiaww (Jan 31, 2006)

*Re: (20AE-2306)*

I did not notice any differance in braking from only using one source of vacuum.


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## aTOMic (Mar 12, 1999)

*Re: PCV Airflow Design (one swell foop)*


_Quote, originally posted by *one swell foop* »_ Any tips on tubing to use? I'm currently using 3/4" heater tubing. Looked around the internet for reasonably priced silicon tubing in that size and was blown away by the ridiculous prices, even for black, which is the color I want.
. 

Hey Swell Foop, BoostController.com has 19mm (3/4") silicone vac tubing for $3.59/ft (min 5 foot) here http://boostcontroller.com/index.php?category=8
Great thread, I love the catch can site, I'm trying to wrap my head around $90+ - could I get the double catch can and use one on each car?







It looks like that'd work, seriously.


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## 01gtiaww (Jan 31, 2006)

*Re: PCV Airflow Design (aTOMic)*

Good site I just ordered 5 feet from them. http://****************.com/smile/emthup.gif By the way I ordered the 3/4 silicone heater hose. I think it would be better for the heat. I noticed the hoses get pretty hot. http://****************.com/smile/emthup.gif 


_Modified by 01gtiaww at 10:36 AM 9-25-2007_


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## 20AE-2306 (Jan 21, 2006)

*Re: (01gtiaww)*


_Quote, originally posted by *01gtiaww* »_I did not notice any differance in braking from only using one source of vacuum.

Yeah like I said you'd have to somehow keep out of vacuum while using the brakes a few times in order to maybe feel a slight difference, I mean the vac booster is there for that purpose. I feel like I noticed it. Maybe try boosting and braking in series and somehow just keep it out of vacuum and see if the pedal gets hard to push...


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## one swell foop (May 7, 2006)

Great! Thanks so much for the link to that site, prices are awesome! I spoke to a sales rep amnd he let me know that they, literally, just got in some silicone vac tubing in the 19mm/ 3/4" size with a thicker wall that they had manufactured specifically for them. It should help prevent kinks and constriction of hoses under any sort of pressure. That product should be up on the site soon, but if you want to order now, then you can call them. I also ordered 6 hose clamps that are the non perforated sort with rolled edges so that it won't cut into the tubing.


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## PainKiller (Oct 3, 2007)

*Re: PCV Airflow Design (20AE-2306)*

Great thread guys, thanks !


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## Micksta (Feb 11, 2007)

*Re: PCV Airflow Design (01gtiaww)*

As for the rats nest of hoses, I simplified things with a catch can. I did not want to eliminate the vacuum source from under the manifold to the lower crancase breather so all I did was I bought a T. 3/8 middle port and 3/4 for the side ports. I connected a line from the middle port of the T into the nipple in the middle of the intake manifold with a one way check valve inbetween, then I ran 3/4 hose for the upper breather off the valve cover teed into the 3/4 hose from the lower cranck case breather into the in of the catch can. As for the out hose back into the intake from the catch can, I eliminated the flying saucer, diverter valve looking thing and just ran a straight hose from the out of the catch can into the intake. My catch can came with 3/4 barbs so everything is still the same size as the OEM system. 3/4 plumbing with both vacuum sources still connected. One vacuum source is for when in vacuum, the other is for when in boost

Great explanation on air flow & your catch can set-up. My PVC hoses under the intake broke & I decided to go with your set up (thanks for posting it!!). Haven't found a check valve at any local auto parts stores for line into the manifold. Did you use any specific type of valve?If so did you get it online? 

_Modified by Micksta at 11:36 AM 2-24-2008_


_Modified by Micksta at 11:38 AM 2-24-2008_


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## Gberg888GLI (Nov 1, 2006)

*Re: PCV Airflow Design (Micksta)*

need to read this is detail later... great thread


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## Abramite (Jun 12, 2007)

*Re: PCV Airflow Design (Gberg888GLI)*

So let me get this right, I have a Catch can that replaced everything in the PCV system. I capped the Vacuum under the manifold. The only thing I kept was the Puck, Do I need the puck? Or because I don't' have a vacuum source I should remove it and run the outlet right into the TIP?
Thanks


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## VWGolfA4 (Apr 5, 2000)

*Re: PCV Airflow Design (Abramite)*

Very good read. Im dropping my car off on Friday to have a catch can put in. The car is smoking at almost every startup...


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## enroscado (May 20, 2009)

*Re: PCV Airflow Design (VWGolfA4)*

Is there anything wrong in just ventilating both hoses that go to the intake (trough the saucer) into the atmosphere?
I just did that, just plumbing the hole in the TIP, and using 2 hoses, 1 for the valve cover vent, and one for the "under the manifold" vent, respectively. Both are just vented into the atmosphere.


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## enroscado (May 20, 2009)

Can anyone help me about what i did (see previous post)?
I don't want to break anything....
Thanks in advance.


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## ypsetihw (Nov 20, 2008)

*Re: PCV Airflow Design (enroscado)*

I found this in my Haynes manual and decided I'd post it for peeps on various PCV threads. Hope this diagram is useful - I think you can splice in right after 16 or right before 11 and keep the rest intact? 








Haynes Diagram H32355
14.1 Turbocharger boost pressure control system (typical)
1. EVAP purge valve
2. Hose
3. Vacuum reservoir (blue balls?)
4. Check valve
5. Turbocharger
6. Wastegate actuator
7. Recirculation air valve (DV)
8. Boost pressure control valve (n75)
9. Power brake booster
10. Air filter assembly
11. Crankcase pressure regulator valve
12. Check valve
13. Fuel pressure regulator
14. Vacuum amplifier
15. Intake manifold
16. Crankcase ventilation housing
17. Recirculation valve solenoid (n249)
18. Vacuum reservoir (on top of the valve cover)
19. Secondary air injection valve
20. Intercooler


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## cincyTT (May 11, 2006)

*Re: PCV Airflow Design (ypsetihw)*

are you seriously going to find every thread and post this? Its alreading in the the FAQ


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## ypsetihw (Nov 20, 2008)

*Re: PCV Airflow Design (cincyTT)*


_Quote, originally posted by *cincyTT* »_are you seriously going to find every thread and post this? Its alreading in the the FAQ









wow LOL
I only posted it to like 3 threads and I was active on two!! 
sorry . . . too many


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