# Info: PCV system diagram and cutaway valves



## zeusenergy (Feb 25, 2008)

So for a while now I've seen many ways of editing the stock PCV system. Decided to do some mods myself only to get flamed. So here's the facts. 
The stock system uses a simple method of drawing air through the crankcase. Fresh air is supplied from the TIP connection at the pressure regulator valve under non-boosted conditions similar to normally aspirated cars. This pre-metered air is allowed to pass through the PCV valve, which under manifold vacuum, will be open and the PCV gases will be drawn into the manifold here. as boost progresses and the pressure builds, the PCV valve closes against it's seat so no pressure is lost. The system reverses and pressure can only back up the Y hose into the TIP. But the TIP is under vacuum now, so it pulls the rubber diaphragm inside the PRV up to the port inside, closing it off. The ONLY passage at this time is a small vent hole in the side of that port. If the pressure inside the PCV system exceeds the ability of the TIP vacuum to draw the diaphragm down to its port, then the diaphragm will be pressed back off the seat and the port is open. The port, seen below, is only 5/16" diameter! 
so if you use a recirculating catch can it may make sense to delete the PRV and use an adapter elbow to attach your TIP hose. 
Anyone who vents atmospherically will have the same ability to vent the gases inside the case, and you may even have better results. Seeing is believing, and I honestly thought the large ports on the PRV meant it had 3/4" of flow. We were all wrong.


----------



## McBee (Aug 11, 2006)

*Re: Info: PCV system diagram and cutaway valves (zeusenergy)*

Good stuff as always http://****************.com/smile/emthup.gif 
Your diagrams were very useful to me last night trying to reroute some vac hoses for a buddy since one of the nipples on the intake manifold broke off.


----------



## zeusenergy (Feb 25, 2008)

*Re: Info: PCV system diagram and cutaway valves (McBee)*


_Quote, originally posted by *McBee* »_Good stuff as always http://****************.com/smile/emthup.gif 
Your diagrams were very useful to me last night trying to reroute some vac hoses for a buddy since one of the nipples on the intake manifold broke off.

Thanks!


----------



## BoostinBejan (Apr 13, 2009)

*Re: Info: PCV system diagram and cutaway valves (zeusenergy)*

Wow, that's teeny tiny!
Good work! http://****************.com/smile/emthup.gif


----------



## zeusenergy (Feb 25, 2008)

*Re: Info: PCV system diagram and cutaway valves (BoostinBejan)*


_Quote, originally posted by *BoostinBejan* »_Wow, that's teeny tiny!
Good work! http://****************.com/smile/emthup.gif 

Sure is. Makes you wonder how these guys are pulling any real "vac" on the system with stock PRV like they claim. 
Most of the time in stock configuration there is little to no vac on the system at all. Barely anything. Maybe enough to keep fumes from building up pressure in the case, which is just what an open atmospheric vent will do.


_Modified by zeusenergy at 1:04 PM 6-2-2009_


----------



## Chickenman35 (Jul 28, 2006)

*Re: Info: PCV system diagram and cutaway valves (zeusenergy)*


_Quote, originally posted by *zeusenergy* »_
Sure is. Makes you wonder how these guys are pulling any real "vac" on the system with stock PRV like they claim. 
Most of the time in stock configuration there is little to no vac on the system at all. Barely anything. Maybe enough to keep fumes from building up pressure in the case, which is just what an open atmospheric vent will do. 

Here would be an interesting test. Can you tee on a vacuum gauge on the PCV hose that exits from the block and measure the vacuum pull? That should tell us how much vacuum the stock system is capable of pulling.
I'm going to do the same thing on a typical small block chevy. It will be interesting to compare figures. 
IMHO. I believe that part reason that VW had such an issue with sludging is inadequate PCV flow. 
Edit: Hmmmm... I wonder is some type of air flow meter might be better? That might give us a better indication of PCV flow amount.
Edit2: Good work!! BTW, please see my apology in your original post. I misunderstood your original concept... DOH 



_Modified by Chickenman35 at 5:07 AM 6-3-2009_


----------



## zeusenergy (Feb 25, 2008)

*Re: Info: PCV system diagram and cutaway valves (Chickenman35)*


_Quote, originally posted by *Chickenman35* »_
Here would be an interesting test. Can you tee on a vacuum gauge on the PCV hose that exits from the block and measure the vacuum pull? That should tell us how much vacuum the stock system is capable of pulling.


Do you mean measure what the TIP can generate? 
That and pure pressure would be the only two tests I could perform now, all my stock stuff is cut to bits.









_Quote, originally posted by *Chickenman35* »_
Hmmmm... I wonder is some type of air flow meter might be better? That might give us a better indication of PCV flow amount.



Now I'm thinking you mean just measure a stock PCV line?


----------



## Andaloons (Apr 16, 2004)

*Re: Info: PCV system diagram and cutaway valves (zeusenergy)*

ZE - you make all your diagrams with Illustrator or something? They are nice.


----------



## hootyburra (Feb 19, 2007)

*Re: Info: PCV system diagram and cutaway valves (zeusenergy)*

sticky


----------



## engineerd18t (Dec 12, 2007)

The thing that bothers me about the PRV location under boost is that:
A: This is where it goes through when you are making the most blowby (at high boost) and
B: I didn't check the pressure in the PCV hoses but there is minimal vacuum in the turbo inlet pipe. I hooked up my boost gauge to the TIP and found to be 2inHG max (this was at higher rpm when the filter turns into a slightly higher pressure drop lol).
For those two reasons I worry about using that as a "vacuum source" unless the pressure in the pcv lines is decent enough to make a pressure differential to move that crap outta the crankcase back into the TIP.


----------



## zeusenergy (Feb 25, 2008)

*Re: (bbeach)*

And that's why VAG chose to go with the large diameter breather hoses from the filter housing and VC. They allow purging of the gases under pressure from the case, not primarily from vac or TIP draw. There are very little restrictions in this setup except for the PRV and PCV valves alone. 
Venting from the stock tee fitting under the manifold like I am works just fine as there are even fewer restrictions than stock, and the diameter of my inlet at the filter is only 1/2 inch long and the same diameter as the PRV interior port. I'll probably still mess with it some more just for fun.








Venting is better than coating sensitive, expensive sensors and TB with grime. Not to mention the crap that hits the intake valves and ports...


----------



## ThegreyT_1 (Sep 30, 2006)

*Re: (zeusenergy)*

ok this seems to be the direction that Im heading......
Can I just delete the PRV puck, plug the hole from the turbo inlet, and run a catch can lines to both of the breather ports??
Im trying to delete the Y pipe and vac reservoir on top of the valve cover.


----------



## sleeply337 (Apr 13, 2008)

*Re: (level_10)*

i too want to get rid of the pvc valve under the intake mani and run straight line from the breather to VC to catch can then ...vent to atmosphere or back to TIP...still debating..


----------



## l88m22vette (Mar 2, 2006)

*Re: (level_10)*

Yes you can just run hosing, see the catch can FAQ in my sig, makes it very straight forward


----------



## elRey (May 15, 2001)

*Re: (l88m22vette)*

Question. 
rule of 'Path of least resistance'
Off-boost: why would fresh air flow from intake tube, thru head/block and then then to PCV valve and intake mani?
Wouldn't it flow straight from intake tube directly to PCV valve and intake mani?


----------



## Slimjimmn (Apr 8, 2006)

pretty sure my pressure reg valve is sticking. I removed it today, cleaned it out with throttle cleaner and put it back in. Idles better now. 
part 06A129101D 19mm size.


----------



## Drewlukyn (May 9, 2019)

Why are the images blocked when I view this?


----------



## CD155MX (Dec 18, 2007)

Drewlukyn said:


> Why are the images blocked when I view this?


Not seeing anything either.


----------



## ackliph (Feb 7, 2012)

CD155MX said:


> Drewlukyn said:
> 
> 
> > Why are the images blocked when I view this?
> ...


Same. Need those images!


----------

