…a little background:

I’ve been wondering about a dual catch can setup for our cars for a while. I’ve asked many questions, consulted many threads, checked other forums and platforms,etc. While I found nothing Audi B8/8.5 related, I found some promising info on VW, subaru and Miata forums.

For our cars, I found a lot of A4’s running the traditional catch can/pcv replacement setup. There are many threads detailing issues with this setup and not many positive results.

A promising setup was the ECS catch can setup installed without the pcv block off cap. Without the block off installed, the pcv retains 100% functionality and the catch can (in theory) catches oil particles before they enter the charge pipe/turbo/intercooler/intake. Great! But this only occurs while the car is actively boosting.

During normal driving, the PCV is doing more work on its “backside” - the side that vents directly into the intake. This is where a dual catch can setup could be beneficial - adding an oil Catcher on the back side. That is what I have achieved (hopefully).

Why am I doing this?
To fill up the engine bay! Just kidding. I checked both ports on my PCV and I had oil dripping from both. In other words, I’ve got oil going through my turbo and into my intercooler. I’ve also got oil going directly into my intake (backside pcv). There were also a few drops of oil in my intercooler piping. See pics - you can see the oil at the pcv breater connection points.

My goal is to have the cleanest charge air as possible as I am in the process of installing a Water-meth kit. I do not want oil vapor taking up space and contaminating my charge air! I am also planning to install an EFR turbo and I do not want oil vapor passing through it. The oil vapor could also reduce the efficiency of my intercooler.

So in short - I hope to catch as much oil vapor as possible before it enters my charge air stream. The catch cans are simply in line filters to the PCV breather pipes - they are supplementary. The PCV retains 100% functionality. My setup has no added check valves - the air can move in both directions.

I will regularly check both cans and will report back on this thread with my findings. I hope to catch nothing but oil. Interested to see if I start collecting water vapor too. It must be noted that any oil that I catch would have been on its way to the combustion chamber. Perhaps my tail pipes will stay cleaner longer!!! Stay tuned. Looking forward to getting some answers based on reality. Let the experiment begin!!!

One final note - I had the ESC kit and had to piece together the catch can setup for the back side. I wanted matched cans so I purchased a second ecs catch can. I would have saved A LOT of money if I had used generic catch cans.

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These are the connectors I had to piece together:
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These are the stock breather connectors that had to be replaced (on the back side PCV).
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