How is a PCV valve not like a check valve? When there is pressure on the manifold side of the valve it will force the valve shut. When there is vacuum on the manifold side, it will throttle the amount of air flowing through the valve depending on the amount of vacuum.

 

This is how I'm building mine, T both pcv ports together, run to vented catch can, then line from catchcan to TB with a check valve. Manifold port will be plugged. This should allow ventilation with and without boost. I'm going to make a homemade catch can with a filter on top and a drain on the bottom.

 

If i am reading your diagram right you are going to have a vacuum leak when the check valve to the intake is open (at idle) and lets air in through the filter on the catchcan.



It needs to be venting when idling. If you plug it at idle then you will have turbo oiling issues and white smoke from the exhaust.

 

Out of boost it would pull air out of the engine through the PCV system, much like stock. Then the breather will vent the engine when in boost.

Basically I'm thinking of a stock PCV system, but put a check valve in the line that goes from the TB to the valve cover, and another check valve in the line that goes from the valve cover to the intake manifold. This will vent the engine when out of boost. Then add a breather line to the valve cover also with a check valve to let air out of the engine when in boost. Basically it would switch between the PCV system and the breather depending on if you're in or out of boost. This will also prevent unmetered air from entering the engine through the breather. Thoughts?

 

[QUOTE=black04;4906063]If i am reading your diagram right you are going to have a vacuum leak when the check valve to the intake is open (at idle) and lets air in through the filter on the catchcan.



I never realized that, thanks. I guess I will cap off the TB as well and run the line and check valve pre turbo?

 

I could be wrong but I dont think that would be enough venting at idle. If you search through threads about people having issues with smoke at idle that is often the cause of it. I put new valve covers on my truck and forgot to unplug the passenger side vent and my garage was filled with smoke in seconds just idling.

You could do that but you do not need a a check valve and you do not need a filter on your catch can. However it would still create a vacuum leak unless you run SD tune or have your maf preturbo and before the fitting for the catch can.

It is essentially the same thing as running both valve covers to a vented catch can except you are drawing a vacuum on both lines.

 

I do something similar to this. I used a sealed catch can and cap off the TB (or valley cover) inlet and the passenger side inlets. Then I cut the oil fill cap and install a breather filter in it. Never had an issue on several builds that way. I can get pics later if that will help.

this would also work if you changed the line from to TB and move it ahead of the turbo/blower and MAF if using a maf. This way it is "metered air" and not looked at as a vacuum leak.

 

Interesting. Is it because the crankcase pressure is preventing the turbo oil from draining properly?

 

Is this diagram accurate to what you mean?

 

Yes.


One potential problem with putting the maf pre-turbo is the blow off valve will throw off the readings.