I spent a lot of time doing DIY posts for my 535, then took a good long break to do some home improvements, then fell head over heels for my 2011 Z4 35is and bought it used 1 year ago.
My first DIY contribution on this forum will be a dual catch can installation.
I prefer to get the job done, then edit and post the relevant information to keep the DIY thread clean but this forum is pretty quite as we all know so I will document as I go and if there are any big mistakes they will get sorted out as we go along. Plus, it will be some fun conversation if anyone is interested.
Parts list, etc. will wait until this is all over and working properly.
What is a dual catch can?
If you have read about the need for doing a walnut blasting to clean the valves... that is what this is all about. I plan to do a walnut blasting myself (maybe another DIY but I am sure there are plenty of those) but before I do I want to minimize the cause of the problem. The cause of the dirty valves is due to the CCV dumping oily, yucky, blow-by sh$t back into the intake, across the valves and back into the engine to be recirculated instead of vented into our precious atmosphere.
Many enthusiasts install a single catch can on the high pressure side only. There are a few points to be made here:
1) This is done because it certainly helps the problem
2) This is done because the high pressure side is accessible and is "easy"
3) What about the low pressure side? This is typically skipped because in our engines it is an internal system that is not readily adaptable to a catch can but is in fact the
primary cause of severe fouling especially in cyl 4,5,6.
So... the low pressure side is where the second catch can in a "dual catch can" goes to trap some of the sh$t before it fouls up the valves.
Edit 11/5/2016: Now that I have installed the low pressure side external conversion PCV valve, I can say it is an excellent part and I have no problem referring others to Rob Beck (rob.rbturbo@gmail.com) for this part. This is not a commercial part with large distribution - Rob designed this part and had it custom made for this application. Well done Rob!