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

[nomunic]

This all looks like interesting and objective data, but getting down to the nuts and bolts, as someone with a 2018 GTI with IS38 upgrade and all accompanying modifications, what do I need to buy? My car just recently started to puff a little smoke upon starting, which is starting to worry me, I'm not going to lie. Car is at 102,500 miles and I don't want to start dumping in thousands of dollars. Don't know if this matters or not but ever since I had a shop do a carbon clean and water pump replacement, there has always been a hint of coolant smell, with no visible leaks under the car. I just recently, roughly 6 months after said work, had my first red check coolant level warning. I don't know if its coincidental to the new smoke, but it has to be something. I've noticed no oil loss, or at least large amounts on the dipstick. Car is rough at idle, rougher than normal, even with EQT grounding wires, OEM RS3 coil packs, and Denso IKH24 plugs gapped to 0.24. I will take a video early this morning so you guys can see. I monitor often with the Accessport, and will get 1 or maybe 2 cylinder misfires at startup/idle. I have never seen smoke during driving, however, and also to note, the car reeks lately, exhaust-wise. So much that upon starting I need to quickly put on the recirculate so my passengers don't get sick. Sorry for the long story, love the car, don't want to spend $40,000 for a lesser new car, yet don't want to start down a rabbit hole with this one, if you understand my concerns.

Smoke on startup is usually valve stem seals, ignore unless it’s realllllyyy bad

 

[scrllock]

This all looks like interesting and objective data, but getting down to the nuts and bolts, as someone with a 2018 GTI with IS38 upgrade and all accompanying modifications, what do I need to buy? My car just recently started to puff a little smoke upon starting, which is starting to worry me, I'm not going to lie. Car is at 102,500 miles and I don't want to start dumping in thousands of dollars. Don't know if this matters or not but ever since I had a shop do a carbon clean and water pump replacement, there has always been a hint of coolant smell, with no visible leaks under the car. I just recently, roughly 6 months after said work, had my first red check coolant level warning. I don't know if its coincidental to the new smoke, but it has to be something. I've noticed no oil loss, or at least large amounts on the dipstick. Car is rough at idle, rougher than normal, even with EQT grounding wires, OEM RS3 coil packs, and Denso IKH24 plugs gapped to 0.24. I will take a video early this morning so you guys can see. I monitor often with the Accessport, and will get 1 or maybe 2 cylinder misfires at startup/idle. I have never seen smoke during driving, however, and also to note, the car reeks lately, exhaust-wise. So much that upon starting I need to quickly put on the recirculate so my passengers don't get sick. Sorry for the long story, love the car, don't want to spend $40,000 for a lesser new car, yet don't want to start down a rabbit hole with this one, if you understand my concerns.

The video at the end of the first post in this thread has the part list in the description.

If you've never changed the PCV I would do so, even if it's the same p/n as what's on the car already. But I suspect you just need to do some diagnostics and have the car inspected for coolant/exhaust leaks.

 

[DerHase]

Big news today:
https://www.facebook.com/share/p/so83YPDuPmzisXsT/

Big win for PCV progress today! It appears we have Jacob’s 2015 GTI now sorted. This is the first smoke-free event he’s ever run using the modified MK8 PCV/full retrofit.
This is a sample 1 of 1 success but looks promising considering he could previously induce smoking easily.
More details/trip report/videos will be coming in the next few days.
Backstory on the 2015-16 GTI problem we set out to solve is covered here, along with the theory/reasoning behind why it was modified to potentially solve this issue:
https://youtu.be/cRznF5fx4rE?si=OQ1PGPxJwLlISoou

Swapped out the MK8 valve that Jacob installed for the one I modified the morning of the event so that we could see if this would allow his car to stop smoking:

Reminder of what it looks like after modification - I used a wood burning hot knife to do this and then just kind of grabbed any stringy bits/flashing off with my fingers. Don't want to use a rotary tool or anything that will create a ton of shavings as they could get into the cam cover (obviously bad), or sucked into the valve itself (clogging the AOS drain, or one of the check valves, etc):

 

[nomunic]

Anyone know the size hose I should get to extend the hose that goes from the PCV adapter to the Venturi/charge pipe? I need to extend it because my gt2260s bung placement will be too far

 

[DerHase]

Anyone know the size hose I should get to extend the hose that goes from the PCV adapter to the Venturi/charge pipe? I need to extend it because my gt2260s bung placement will be too far

For running a boost hose to the Venturi? It's 3/8in at the Venturi, but I'd recommend a 1/4in ID hose from one of your charge pipes and then adapt it up to 3/8in right before the Venturi barb.

 

[nomunic]

For running a boost hose to the Venturi? It's 3/8in at the Venturi, but I'd recommend a 1/4in ID hose from one of your charge pipes and then adapt it up to 3/8in right before the Venturi barb.

This is all I got rn l, ran the Mishimoto piece into the rubber pipe, then ran the 90 degree barb. I used another barb then connected to mk8 portion

 

[DerHase]

Yeah that should do. Just make sure that fitting is sealed 100% and should be good to go.

 

[nomunic]

Yeah that should do. Just make sure that fitting is sealed 100% and should be good to go.

Yes I’ll spray some soopy wudder on it

 

[nomunic]

Yeah that should do. Just make sure that fitting is sealed 100% and should be good to go.

Well after a short ride and getting into some boost, even after retightening a trying again, the mishimoto adapter will not stay in place and blows out. I cut the hole extremely small and had to really force it into place, so that shouldn’t be an issue. I would say to most to stay away from that workaround.

 

[SaucyMuffin]

The video at the end of the first post in this thread has the part list in the description.

If you've never changed the PCV I would do so, even if it's the same p/n as what's on the car already. But I suspect you just need to do some diagnostics and have the car inspected for coolant/exhaust leaks.

I've replaced the air/oil separator rather recently but just for piece of mind today replaced it again with a new N80 purge valve and the hosing. My inlet pipe was rather clean and the turbo had little oil. And whether it was a coincidence or not, no puff. I'm still having it looked at but for the small price and piece of mind, I hope that I'm going in the right direction. Thanks again guys!

 

[DerHase]

Forgot to add, but here's the trip report from the autocross event with a bit more info:
https://www.datadrivenmqb.com/tripreports/2024tsccax6

On a side note: 2 other people who originally had issues smoking on the full retrofit on the street were able to ventilate their PCV and they've also not been able to duplicate the smoking since (had them both try to induce smoking in the same spot as before). All of the blue shaded stuff used to be red.

 

[Klrider44]

Forgot to add, but here's the trip report from the autocross event with a bit more info:
https://www.datadrivenmqb.com/tripreports/2024tsccax6

On a side note: 2 other people who originally had issues smoking on the full retrofit on the street were able to ventilate their PCV and they've also not been able to duplicate the smoking since (had them both try to induce smoking in the same spot as before). All of the blue shaded stuff used to be red.

View attachment 308398
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So what exactly is being done to get these results?

 

[DerHase]

So what exactly is being done to get these results?

Collecting the info?
I'm reaching out to anyone I see having issues or running a full retrofit successfully to try and find trends. I try to keep it updated as much as possible. I've put a few of the problems w/ basic retrofit on there mainly to run VINs for part numbers.

If you mean the 15-16 cars running full retrofit without issues, the PCV modification mentioned here has helped. 1 on track and 2 on the street so far.

Trip report regarding the PCV modification experiment:
https://www.datadrivenmqb.com/tripreports/2024tsccax6



If I recall correctly, you did the retrofit but got some smoking right? Basic or full? I have you down as basic on that page. You may need to burn a hole in the bottom of the PCV to do the same as well.

I've ordered another valve myself so I can get a video modifying it/how not to fuck it up.

 

[Klrider44]

Collecting the info?
I'm reaching out to anyone I see having issues or running a full retrofit successfully to try and find trends. I try to keep it updated as much as possible. I've put a few of the problems w/ basic retrofit on there mainly to run VINs for part numbers.

If you mean the 15-16 cars running full retrofit without issues, the PCV modification mentioned here has helped. 1 on track and 2 on the street so far.

Trip report regarding the PCV modification experiment:
https://www.datadrivenmqb.com/tripreports/2024tsccax6



If I recall correctly, you did the retrofit but got some smoking right? Basic or full? I have you down as basic on that page. You may need to burn a hole in the bottom of the PCV to do the same as well.

I've ordered another valve myself so I can get a video modifying it/how not to fuck it up.

I have the full kit, I did purchase the knockoff BMS catch can but haven’t installed it yet. If that doesn’t have any effect on things I am def willing to try the modified top plate.

 

[DerHase]

I have the full kit, I did purchase the knockoff BMS catch can but haven’t installed it yet. If that doesn’t have any effect on things I am def willing to try the modified top plate.

Roger.

I know you're not tracking the car, but the guy in the video with the 2015 Audi A3 has that same can and it didn't do anything for him on track.




I'm honestly starting to wonder if there might be a physical difference in the block passageways in the 2015-16 CXCA/CXCB/CNTA engines vs 17+ stuff. Perhaps the piston rings are just a coincidence? I find it hard to believe there is such a (seemingly) large amount of blow-by that hasn't shown up on any compression or leak-down tests thus far (with one exception of a guy with a broken piston/ring).