Exactly, i forgot to tell that the picture is the config "2" that do not work...Basically, all lines are connected to the crankcase, so the pressure should be roughly the same wherever you connect it ... but in reality the pressure pumps up at each ignition due to leaks, so it is interesting to have the oil return line at a different location versus breather line. Also it is preferred to have it the lowest, thus gravity helps oil to return.
From my experience, here is some basic rules to have in mind to lower oil consumption by breather port:
- Reduce air flow : a good condition of cylinders/piston/rings will reduce air leaks that need to be rejected threw the breather
- Lower oil content in air : the lower oil content is at separator inlet, the lower the oil content will be at separator outlet ...
the breather port location is important; also here gravity helps, in most of case original location is on top of crankcase. In case of continental with no starter, it looks like top of starter cover plate works also quite good.
- internal design of separator : it is a combination of
* centrifugal load : inlet enters tangential to the wall to have oil coalescing on separator walls
* air velocity change : when air enters separator, it slows down, then reaccelerate to go out. Oil having a higher density than air, they separate. the higher internal volume, the better the separator will work.
* gravity : outlet is normaltime on top and shifted from the wall
- the oil separated need to escape the separator fast and easily
- in case of continental
* the aerobatic type breather assy helps reduce oil in air
* the vacuum pump gear needs to be removed from camshaft to avoid agitating oil close to breather; adding an oil return line between vacuum pump and sump to avoid the cavity to remain full of oil close to breather location.