Originally Posted by Xist
The drain is at the top of the oil pan?
As Joris and RobertISaar have stated the turbo oil return return line must be above the oil level in the oil pan. The turbo oil return line usually uses gravity to return the oil back to the oil pan. Crankcase pressure is very critical because once crank case pressure reaches a certain point it will affect the turbo's oil flow back to the oil pan.
Now a couple other hurdles I'm working out.lol
On a high HP turbo engine at high load WOT you have a ton of engine blow-by which equals high crank-case pressure. The turbo adds even more pressure to the crankcase at high load WOT when its making boost. Turbo's are designed to have higher pressure on the compressor side and turbine side of the oil seals of the center cartridge to keep oil from getting into the compressor and turbine housing (just like piston compression rings). The downside of this is it adds more pressure to the crankcase. Pressure flow past the seals inward toward the center housing and adds pressure to the turbo oil return-line and then the oil pan.
On my engine at WOT high load the turbo oil return will have some help with return oil flow because I'm using a Tilton oil pump to draw oil from both turbo's and return them through the oil pan fitting in my pictures.
So right now I'm working on routing the oil return lines so both of them are on a downward slope back to the oil pan. I'm also adding a "by-pass valve" to by pass the Tilton pump for light load FE conditions.
This part of my build has been the most time consuming and starting to burn me out. But I'm getting closer.