Could write an entire chapter on this alone.
There really isn't a QC issue worth looking into.
What is important is recognizing the difference between a failure and a system operating outside the scope of what the PCV can manage.
7
Understanding the MK7 PCV function, retrofitting the MK8 PCV, and why catch cans are bullshit(IMO)
- Thread starter DerHase
- Start date
There really isn't a QC issue worth looking into.
What is important is recognizing the difference between a failure and a system operating outside the scope of what the PCV can manage.
I've seen brand new PCV's smoke on the same exact car, replaced and not smoke. Small sample size, but 2 of the 3 cars in our autocross club had issues with brand new BL PCV's, but minimal or no issues with new older versions.
DerHase
Autocross Champion
- Location
- Hampton Roads, VA
- Car(s)
- 2019 GTI Rabbit
To be clear they installed non-BL PCVs and had less problems?
I think some of the PCVs are better suited to certain year cars (and/or certain combos of parts). Hence why @mrmatto (2015 CXCA) has had best luck with the AH/AP and smoked on the BL, but you had best luck with a BL (2019 DKFA).
Installing one of those "bad" valves on your car and your "working" BL valve on the cars in question would be a lot more relevant to determining if a PCV is bad out of the box.
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ucfquattroguy
Go Kart Newbie
- Location
- Florida USA
Another unscientific example, but Misha posted a ring lap in the last week in a stock Mk7.5 TCR edition GTI. Factory IS38 w290hp output. No smoke.
iwannagofast
Not a Newbie
- Location
- Severn, MD
- Car(s)
- '17 GTI
Just wanted to post an update since my last post about my turbo leaking oil through the turbine "seal" on page 32 or so. Turns out my turbo was blown, front to back movement in the cartridge and a lot of the veins on the turbine blade were cracked, probably from rubbing on the housing. Looks like I caught it before it got any worse. I've shipped it back to the manufacturer to be refurbished. It looks like the increased pressure from the PCV replacement plates just exacerbated the turbo issue since the oil wasn't draining as quickly from the housing. In the mean-time, I've swapped back to my IS38. I still have my MK8 PCV, MK7 PCV (w/ ECS PCV to AN conversion), and 034 PCV plate as well as my APR catch can... so...I don't know which to put on once I get the XL back. At this point, I don't know if the turbo went bad on it's own and that's what caused the leak or if the excess crankcase pressures caused the turbo to fail. Fun stuff...
I saw that, bizarre... almost all ea888s in that channel are a smoke show, especially the carousel section
Untuned on 300TW tires, makes sense. Most of the others have been a mess of engine modifications and/or sticky tires.
DerHase
Autocross Champion
- Location
- Hampton Roads, VA
- Car(s)
- 2019 GTI Rabbit
So did a little bit of science tonight. I plugged the TMD boost port that I've been using to run the Venturi, and plugged 6ft of vacuum hose to my gauge again to the Tiguan hose top port get some baseline numbers at WOT to see how much vacuum is being generated at the turbo inlet pipe at WOT.
Low boost levels (17psi basically flat). This was kind of an afterthought right before we got home, and due to our turn ahead coming I shifted at 5500rpm and lifted a bit early.
Result: 10-11inHg. Will be sure to retest again and do a few pulls to redline. Testing lower power really sucks because it gets there SO DAMN SLOWLY.
https://youtube.com/shorts/H5h_bwZvxg8
Note: I originally notated this as "stock" boost levels... Regardless it's an incredibly weak tune and is about the most you'd ever see (peak) from a stock file anyway.
26 tapered to 19 psi boost levels. Vacuum peaked at 15inHg a bit before 5500rpm FWIW. I did test this like 4 times in a row all with consistent readings.
Result: 15inHg.
https://youtube.com/shorts/Y4NpE_Wzjpg
IMO this doesn't necessarily mean much of anything by itself. But it's a baseline for a car that doesn't suck oil up when driven on track/auto-x (even when it was in basic retrofit form).
The following hypothesis are strictly for operating like designed at WOT, ignoring braking/turning/etc:
I suspect ideally the diaphragm remains fully closed/sealed at WOT, but just barely so that as pressure is built up in the bottom end, it is relieved slowly but immediately as it just barely cracks open.
If it operates wide open (poor vacuum at TIP under WOT, for the given amount of blow-by which we can't really quantify), then oil will constantly flow to the point it can overwhelm the AOS.
If it is sucked shut so far/so hard by excessive vacuum (if that's possible?), then it might allow pressure to build in the crankcase. The intake manifold generates 20inHg at idle roughly.
With all the above, I have a feeling it's a combo of turbo/boost pressure/intake parts that can keep the OEM style PCVs happy.
As for the braking/turning problems I'm personally more interested in solving:
The above all happens, but as soon as you let off the brakes, it gets intake manifold vacuum, but getting back on the throttle you lose all vacuum momentarily. When this happens, the diaphragm opens 100% under spring pressure. Vacuum builds again and due to the pressure differential it's pulling stuff upwards, hit the brakes, repeat.
The Venturi I think will be the key for this particular issue. I don't know of any MK8s that have had widespread problems yet, and seen several of them tracked/autocrossed and tuned on 200TW tires. If the crankcase never fluctuates in pressure, and you have at least "enough" vacuum at WOT, there won't be any opening and closing of the diaphragm, and no large pressure differentials to push oil upwards.
Low boost levels (17psi basically flat). This was kind of an afterthought right before we got home, and due to our turn ahead coming I shifted at 5500rpm and lifted a bit early.
Result: 10-11inHg. Will be sure to retest again and do a few pulls to redline. Testing lower power really sucks because it gets there SO DAMN SLOWLY.
https://youtube.com/shorts/H5h_bwZvxg8
Note: I originally notated this as "stock" boost levels... Regardless it's an incredibly weak tune and is about the most you'd ever see (peak) from a stock file anyway.
26 tapered to 19 psi boost levels. Vacuum peaked at 15inHg a bit before 5500rpm FWIW. I did test this like 4 times in a row all with consistent readings.
Result: 15inHg.
https://youtube.com/shorts/Y4NpE_Wzjpg
IMO this doesn't necessarily mean much of anything by itself. But it's a baseline for a car that doesn't suck oil up when driven on track/auto-x (even when it was in basic retrofit form).
The following hypothesis are strictly for operating like designed at WOT, ignoring braking/turning/etc:
I suspect ideally the diaphragm remains fully closed/sealed at WOT, but just barely so that as pressure is built up in the bottom end, it is relieved slowly but immediately as it just barely cracks open.
If it operates wide open (poor vacuum at TIP under WOT, for the given amount of blow-by which we can't really quantify), then oil will constantly flow to the point it can overwhelm the AOS.
If it is sucked shut so far/so hard by excessive vacuum (if that's possible?), then it might allow pressure to build in the crankcase. The intake manifold generates 20inHg at idle roughly.
With all the above, I have a feeling it's a combo of turbo/boost pressure/intake parts that can keep the OEM style PCVs happy.
As for the braking/turning problems I'm personally more interested in solving:
The above all happens, but as soon as you let off the brakes, it gets intake manifold vacuum, but getting back on the throttle you lose all vacuum momentarily. When this happens, the diaphragm opens 100% under spring pressure. Vacuum builds again and due to the pressure differential it's pulling stuff upwards, hit the brakes, repeat.
The Venturi I think will be the key for this particular issue. I don't know of any MK8s that have had widespread problems yet, and seen several of them tracked/autocrossed and tuned on 200TW tires. If the crankcase never fluctuates in pressure, and you have at least "enough" vacuum at WOT, there won't be any opening and closing of the diaphragm, and no large pressure differentials to push oil upwards.
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In my experience when stock they are less likely to smoke. I tracked my Clubsport (CJXE) for 3 years stock tune on the stock pcv and never had smoke. After tuning I started to have issues and put on a plate.
DerHase
Autocross Champion
- Location
- Hampton Roads, VA
- Car(s)
- 2019 GTI Rabbit
Out of curiosity, was the intake/TIP ever changed from stock before or after tuning?
Less likely but still they can have these issues. Ive been having this issue since it was stock, now its stage 1
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tigeo
Autocross Champion
- Location
- Richmond, VA area
Just a gratuitous shot of my MK7 BL PCV. Just look it...sitting there...ready to smoke some perfectly good High Performance Lubricants Euro 5W40 oil coming out of T1 at VIR but choosing wisely...and not doing that b/c it's a good little PCV.
If memory serves I believe I changed both of those prior to tuning.
DerHase
Autocross Champion
- Location
- Hampton Roads, VA
- Car(s)
- 2019 GTI Rabbit
Minor update on what’s been getting worked on:
I put my vacuum gauge to the top port of the Tiguan hose, essentially turning it into a measurement of how much vacuum is being developed at the TIP (aka the strength of the vacuum source under WOT).
Also note I have an OEM air filter/TIP etc. Mechanically the car is stock aside from an intercooler + catted downpipe.
Here are the results with a stock-ish tune/boost levels:
https://youtube.com/shorts/H5h_bwZvxg8?si=SpsKg2KowC3THKpQ
And with boost upped:
https://youtube.com/shorts/Y4NpE_Wzjpg?si=FU6doZKhM_ZD5r-7
So roughly 10inHg at stockish levels, and 15inHg when tuned.
I found a local guy (Nick) who has a S2 IS20 EQT tuned GTI who retrofitted (basic) the MK8 valve. He also has a CTS v2 TIP and an IE v2 intake.
Anyway we put the gauge on his car the same as mine…
https://youtube.com/shorts/4Zmto9yHD9s?si=ReTYaaQcbUCKRw1p
In a nut shell:
Stock = 10inHg
Tuned = 15inHg
Tuned w/ TIP + aftermarket intake = 2.5inHg
So this means under WOT the diaphragm will be wide open (or close to it) because there’s not enough “excess” vacuum to overcome the spring pressure of the diaphragm.
I’m NOT sure if “too much” vacuum is a thing, though I suspect it can be.
Not sure how much change is from TIP, and how much is from intake.
Need to test a few more cars, one of which will be a 2260 car.
I got all the stuff to wire up the PCV sensor for logging purposes, so hopefully can get that all sorted over the holidays and start logging pressure direct inside the valve itself which is really what should be all that matters. Perhaps will buy a cheap TIP in the name of science to get some answers.
I put my vacuum gauge to the top port of the Tiguan hose, essentially turning it into a measurement of how much vacuum is being developed at the TIP (aka the strength of the vacuum source under WOT).
Also note I have an OEM air filter/TIP etc. Mechanically the car is stock aside from an intercooler + catted downpipe.
Here are the results with a stock-ish tune/boost levels:
https://youtube.com/shorts/H5h_bwZvxg8?si=SpsKg2KowC3THKpQ
And with boost upped:
https://youtube.com/shorts/Y4NpE_Wzjpg?si=FU6doZKhM_ZD5r-7
So roughly 10inHg at stockish levels, and 15inHg when tuned.
I found a local guy (Nick) who has a S2 IS20 EQT tuned GTI who retrofitted (basic) the MK8 valve. He also has a CTS v2 TIP and an IE v2 intake.
Anyway we put the gauge on his car the same as mine…
https://youtube.com/shorts/4Zmto9yHD9s?si=ReTYaaQcbUCKRw1p
In a nut shell:
Stock = 10inHg
Tuned = 15inHg
Tuned w/ TIP + aftermarket intake = 2.5inHg
So this means under WOT the diaphragm will be wide open (or close to it) because there’s not enough “excess” vacuum to overcome the spring pressure of the diaphragm.
I’m NOT sure if “too much” vacuum is a thing, though I suspect it can be.
Not sure how much change is from TIP, and how much is from intake.
Need to test a few more cars, one of which will be a 2260 car.
I got all the stuff to wire up the PCV sensor for logging purposes, so hopefully can get that all sorted over the holidays and start logging pressure direct inside the valve itself which is really what should be all that matters. Perhaps will buy a cheap TIP in the name of science to get some answers.
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PerceivedShift
Autocross Champion
- Location
- Virginia
Ohh this is interesting, could it be that some TIPs don't properly create nearly enough vacuum at the TIP? It needs a given air velocity to have a chance at providing enough vacuum. Some TIPs are designed to just act as a small "intake plenum" with really no thought as to how air will pass over the PCV line without any fluid dynamics modeling. I guess everyone just assumes enough air passes through to keep it happy. Look how this CTS V2 TIP is designed:
CTS just made the pipe "wider" but the inlet and outlet diameters of course remain the same. This would create all kinds of turbulence inside the TIP potentially without increasing flow AT ALL. Perhaps a hybrid turbo would generate more vacuum with this CTS V2 TIP but who knows how much more and how fast? Regardless, dumb design! If you're gonna fatten up that TIP (Gawd that sounds dirty) you better fatten the pipe all the way to the air filter.
CTS just made the pipe "wider" but the inlet and outlet diameters of course remain the same. This would create all kinds of turbulence inside the TIP potentially without increasing flow AT ALL. Perhaps a hybrid turbo would generate more vacuum with this CTS V2 TIP but who knows how much more and how fast? Regardless, dumb design! If you're gonna fatten up that TIP (Gawd that sounds dirty) you better fatten the pipe all the way to the air filter.