Confirmed: Turbo Inlet Pipes can Break the PCV System

So this has been a long time coming… it turns out that due to the inherent design of our PCV system:

• Diaphragm to control crankcase vacuum

• Pulling that vacuum directly on the bottom end

• Turbo inlet pipe is the only vacuum source at WOT

… replacing the turbo inlet pipe (and to a much lesser extent, adding boost) has a HUGE influence on how well an OEM PCV can work (this goes for MK8 basic retrofit, and all MK7 valves as well since the function is fundamentally identical). The MK8 full retrofit w/ the Venturi doesn’t really care what TIP is used, and actually seems to work better with those that generate less vacuum.

It’s a long topic and I wanted to get deep into the data and try to cover as many bases as possible, so here is a link to the video going over it all. It includes:

• Bench testing of the diaphragm to see how it works

• Comparisons of stock boost levels vs tuned

• Multiple aftermarket TIPs tested for both crankcase and PCV vacuum levels

• Why 2nd vs 3rd gear makes a big difference (and autocross is hell on a sub-optimal system)

• Camera aimed at the diaphragm to confirm what was suspected based on the data

• Realistically what you need to worry about (or not). Spoiler alert: if you’re not tracking or autocrossing your car, it’s MUCH less of a big deal.

And here is all the data from the video to go along with it (somewhat cleaned up/reorganized for clarity). If any new TIPs get tested, they may be added here in the future.