just for ***** and giggles and to stir up the pot. My 12v ran like 80-100 when cold and like 40-60 when warm. I would think 40 would be perfect. I think feeding a turbo is more of just making sure you have oil to it. Cummins spec for oil pressure is min 10psi. So if the turbo can last with as little as 10psi i think you are good to go
On edit: This is striaght from the HX35 HX40 Holset manual. Might try to find a manual for the HE But here
11. Oil return pipes are permitted to decline at an overall angle of not less than 30 degrees below horizontal.
All turbocharger applications require a pipe of internal diameter greater than 19 mm which has integrated
connectors. To ensure oil drains into the engine under all operating conditions, the return connection
into the engine sump must not be submerged and the outlet flange of the turbocharger must be 50 mm
above the maximum oil level of the engine sump pan.
13. Oil pressure of 150 kPa (20 lbf/in2) must show at the turbocharger oil inlet within 3 - 4 seconds of engine
firing to prevent damage to turbocharger bearing system. A flexible supply pipe is recommended.
14. The minimum oil pressure when the engine is on load must be 210 kPa (30 lbf/in2). Maximum
permissible operating pressure is 500 kPa (72 lbf/in2) although 600 kPa (88 lbf/in2) is permitted during
cold start up. Under idling conditions pressure should not fall below 70 kPa (10 lbf/in2).
15. Recommended oil flows for the turbochargers are 2 litre/min at idle and 3 litre/min above maximum
torque speed.
Note:
100 kPa = 1 bar (14.5037 lbf/in2 =psi).