[Snoman002]

So, not another pcv valve, valve cover thread.

In changing the charge pipe there was a lot of oil in my intake and I'm adding a catch can.
The hope was to tap into the pcv valve off the valve cover and be done, but now looking at it I would like to understand more of the system.

On the passenger side is valve cover with the pcv valve. That appears to feed into the low side of the intake and nowhere else.

On the charge pipe, the high side, is the hose by the throttle body. I originally thought this was the pcv side, but now I question that.
The high side hose comes out of the charge pipe and hits a "T", one side going to the low side intake pipe (but not pcv). This appears just to be airflow around the turbo (but why?).
Off the other side of that "T" it goes to another valve. One port of this valve goes to the gas tank. The other port of this valve disappears under the throttle body and I cannot trace it.

So where is the high side picking up crankcase ventilation from?

There is also another vacuum line that comes off the valve cover, runs across the motor and goes into what I am guessing is the hpfp.

Any more details so I can understand more?

[Houranimd49]

I could be wrong but based on my observations, that annoying brittle crank vent hose that breaks when you look at it is mainly responsible. I attached a photo of it.

I suspect this because the name of the part itself, and this is where you split the line here to attach a catch can.

[Snoman002]

Thanks for the confirmation as that was where I was planning to tap into the system.

I guess my next question, maybe the question I was really looking to answer, is does the high side (pressurized, post turbo) pull in crankcase vapors? And if so, from where.

[Snoman002]

Hmm, looks like I have my highside/lowside backwards.

[Snoman002]

So, more digging since the n55 is something I have not dealt with before and I don't want folks to read above and think that is correct. Plus it took a LOT of threads to piece this together.

High side pvc is the tube on the passenger side going into the intake (pre turbo). This is the hose that often breaks and also has the little heater in it. This is the area where most put an oil catch can (occ).

Low side is all internal. Routing in the valve cover lead directly into the intake ports on the head. No real way to put in an oil catch can without major mods.

The hose I spoke about, the one that runs from the charge pipe across the engine to the intake is for evaporative emissions. It connects to the charge pipe and to the back of the throttle body. When the engine is not under boost (vacuum in the charge pipe) the fuel vapors are pulled into the charge pipe and into the throttle body. When the turbo is making boost this pipe bleeds boost through that pipe back into the intake pipe. There is a little valve in there that as the air flows from the charge pipe to the intake it creates a vacuum on the evaporative emission piping (if the valves allow it) and draws fuel vapors over to the intake. The turbo is basically blowing fuel vapors over into the intake upstream of the turbo.


Ultimately I still need to figure out where my oil vapors are coming from. First step is to ensure there is a low noack oil in there as opening the oil cap had oil vapors in the crankcase even 30 minutes after shutting off the engine