PCV System Knowledge Dump
2 Years of Knowledge, in a Nutshell
Why this video was made
This MK7 (and MK8) PCV research started in July of 2023 and turned into way more than I had originally anticipated. I know that everything learned is spread all over the place between different videos/articles on the website so I wanted to take a minute to go over the bare essentials in understanding the different factors at play when considering a PCV system change. This video was really tough to put together when trying to cram 2 years of learning into such a short timeframe. It doesn’t go terribly far into the intricacies of how the OE valves work or ALL the differences between them and plate systems, but I think conveys the necessary points.
While this video might not definitively say what you should or shouldn’t do, it should enable a more accurate risk assessment for any potential solution being considered.
As always, if you’re viewing this video way after it was published, the most recent information is kept updated at https://datadrivenmqb.com/mk8pcv.
Funny observations
Since I didn’t have time to specifically say this in the video, I’ll do it here: based on all these lessons learned over the past couple years, it’s interesting to look at older forum posts and see how some of these factors led to so much confusion on this platform:
The BL PCV valve was previously touted as the newest “revision” and people were confused as to why VW put them on 2019 Golf Rs but nothing else. People considered it an “upgrade” when in reality it was designed very differently for a very specific reason. Once again, VW knows best.
Turbo inlet pipes were normally one of the first “upgrades” people made to their car, and nobody in the 8-9 years prior did proper A/B/A testing if they experienced smoking issues after install. It was previously believed to just be a stupid tube. This was probably the most significant discovery in my personal opinion.
Some people believe that a PCV plate is the ONLY option for fixing smoking problems. While it is true that at some point all OEM valves can get overwhelmed, the fact is a lot of people were causing their own problems (see turbo inlet pipes above). Due to the variation in engine components over the years, I think a LOT of the people who make this claim had early cars, which seem to have all the odds stacked against them. It may be necessary for hard track use on the early cars, but later cars can get away with a properly functioning OE PCV system in many cases, even in track use. To be clear: If it’s a dedicated track car or you do a considerable amount of track time, I’ll concede that a good plate system probably makes the most sense.
Unfortunately this type of misinformation started to happen with the MK8 retrofit as well. While I’ve continued trying to learn and understand more, releasing videos/articles as quickly as possible, I was observing people with PCV problems being immediately told “Do the MK8 retrofit”. No context of what year vehicle they have, how much power, how they’re using it, etc. This was happening well after I had shared the Parts Catalogue video/article. This was a big motivation into putting all of these vital points into a single video while making it short and concise.
Random thoughts
The previous thinking of the BL valve being an “upgrade” I don’t think was necessarily an illogical assumption. It is a factory part installed on a very similar car that makes more power from the factory.
The only real problem was mixing a block-passage breathing valve on a long block originally meant for a cam cover breathing valve. Since the BL (19+) and BM (15-18) valves originally came on IS38-equipped vehicles, it’s entirely possible that the following MK7 valves can be changed relatively safely, and MIGHT be more suitable for tuned and/or IS38-swapped GTIs and 1.8L cars:
AP => BM (both breathe on the cam cover)
BK => BL (both breathe on the block passage)
This is just a hunch/theory of mine in the meantime, and it’s important to remember that if you’re not running an OE turbo inlet pipe, all bets are off regardless of which MK7 valve you run.
I’ve not been able to compare AP vs BM, but the BK vs BL only difference I have noticed is a VERY small difference in the diaphragm center orifice diameter. It is actually a tiny bit smaller on the BL valve. We’ve learned that more power equals more vacuum source at the turbo inlet pipe… all else being equal. So it’s my theory that the Golf R has a slightly smaller orifice in the valve to maintain roughly the same overall flow through the diaphragm to compensate for the stronger vacuum source.
Realistically thinking, I believe the difference is small enough that it really won’t matter much one way or the other, as long as you have the correct style (block passage vs cam cover breathing) valve.
