MK8 PCV Follow-Up and more Tech Talk

This video is going over some of peoples’ experiences with retrofitting the MK8 PCV. The cars with problems also prompted some more questions which puts us further down the rabbit hole with more stuff to look into.

I did not go super in-depth in the video about WHY I suspect the TIP and/or air filter are significant, but if you take a look at the testing done by Flat Irons Tuning on Subarus… you’ll find that adding a cold air intake drastically lowered the vacuum generated from the TIP at wide open throttle. Forward to the 8:30 mark for the relevant part to this point, though I encourage watching the entire video as well.

In a nut shell, they found that more boost causes a deeper vacuum to be pulled. Conversely they found that adding a free flowing intake caused a LOSS of vacuum. Subarus do not have terribly complex PCV systems, but on our MK7s, all of the TIP vacuum gets drawn across the diaphragm, which as explained at the 20:01 timestamp of the PCV Update video, is just a simple regulator. Lessening the amount of vacuum on the WOT source side, means that the diaphragm will operate in a wider-open state allowing oil to pass through even easier.

As always, this will require some more testing. I’m currently working on wiring the MK8 PCV sensor to my car for actual data logging with better resolution, at which point I will be better able to test the effects of intake changes.