Understanding the MK7 PCV function, retrofitting the MK8 PCV, and why catch cans are bullshit(IMO)

[avenali312]

I changed my first PCV on Sunday evening. Do I get to be a PCV Bro now?

 

[DerHase]

Two different aftermarket TIPs, both in basic retrofit form... one of them operates with the diaphragm wide open at any time under throttle...

 

[PerceivedShift]

All of us were so quick to blame the PCV...when we were the problem all along.

 

[tigeo]

All of us were so quick to blame the PCV...when we were the problem all along.

 

[Mosquito]

The MK7 PCV wasn't without its flaws, but looking at what VW did with the MK8 revision, we clearly didn't do ourselves justice.
Some of it came down to parts used, some of it came down to tuning strategies or consequence of added power. The reality is that nobody outside of VW has had a good understanding of this "emissions" part.

 

[mrmatto]

I mean, some of us smoked on a totally stock setup too. That’s what led many to trying other things. Aftermarket TIPs are prob making the problem worse, but…

So far, my most successful combo is AP PCV and BMS catch can.

Once @DerHase’s testing is done, I’ll probably try the full mk8 retrofit with the Venturi.

 

[Mosquito]

I mean, some of us smoked on a totally stock setup too. That’s what led many to trying other things. Aftermarket TIPs are prob making the problem worse, but…

stock setup as in a completely stock car on a track event? I don't imagine anyone fully stock is smoking on the street as it would likely become news and force VW to address it. That said, when looking at max vacuum across ends of the rpm range, the draw is low enough that quite a few things can alter it, even between different cars in stock form. Loosing -1 inhg across worn seals is very little but quite a bit in a car only pulling -2 inhg on either side and specially on/off throttle where the crankcase looses vacuum. That is specially harsh in autocross and 2nd gear pulls. Much more so than circuit events.

 

[mrmatto]

stock setup as in a completely stock car on a track event?

Yeah I got knock on right handers at one autocross event running a stock tune on the stock AH pcv with no catch can. Adding the can made all the difference for me. But the point is the stock setup isn’t up to the task even before we fuck with it. Especially when you start running more boost, of course.

 

[GTIfan99]

I mean, some of us smoked on a totally stock setup too. That’s what led many to trying other things. Aftermarket TIPs are prob making the problem worse, but…

So far, my most successful combo is AP PCV and BMS catch can.

Once @DerHase’s testing is done, I’ll probably try the full mk8 retrofit with the Venturi.

I still think you got a bad BL. We should put mine on your car.

That or maybe you have an aftermarket TIP and just don't know?

Dundundun. The plot thickens. Stay tuned to PCV Theatre...

 

[GTIfan99]

Yeah I got knock on right handers at one autocross event running a stock tune on the stock AH pcv with no catch can. Adding the can made all the difference for me. But the point is the stock setup isn’t up to the task. Especially when you start running more boost, of course.

You got smoke on the street with your BL, didn't you?

 

[Mosquito]

Once @DerHase’s testing is done, I’ll probably try the full mk8 retrofit with the Venturi.

What are you looking for it to conclude? Honestly curious. You'll never re-install the MK7 one again.

 

[mrmatto]

You got smoke on the street with your BL, didn't you?

Yeah the BL sucked. I don’t remember if it smoked but I def got knock and oil consumption just driving around normally. Maybe it was bad or maybe it’s incompatible with the CXCA.

 

[mrmatto]

What are you looking for it to conclude? Honestly curious. You'll never re-install the MK7 one again.

I’m not looking for a specific conclusion. Just waiting for all the test variations and data to be wrapped up so I can consider it all holistically.

 

[GTIfan99]

What are you looking for it to conclude? Honestly curious. You'll never re-install the MK7 one again.

I'm looking for an OEM solution to my car smoking on track without having to check and empty a CC after every session.

 

[Mosquito]

Yeah I got knock on right handers at one autocross event running a stock tune on the stock AH pcv with no catch can. Adding the can made all the difference for me. But the point is the stock setup isn’t up to the task even before we fuck with it. Especially when you start running more boost, of course.

Yeah. I found oil tends to prefer the cylinder 4 drain port once oil makes it up to the PCV assembly. Makes sense for Gs to further push it that way on right hand corners. Braking pushing oil forward in the oil pan, towards the pickup tube on the wyndage tray, a crankcase loosing vacuum, followed by massive vacuum from the intake port 2-3 seconds after braking seems to be the recipe. Usually happens on the 2nd repetition, since getting back on boost quickly can potentially push some oil back the drain port the first time, but another vacuum event and it really draw it out.