I think i have sorted out the oil drain issues i was having last week. I have fitted a 0.035" diameter (0.619mm^2) oil restrictor down from the 1mm (0.785mm^2) restrictor i originally used. The 0.035" is 0.889m diameter. So about a 10% reduction in diameter, or a 22% reduction in cross sectional area and im guessing flow. I also ordered a 0.030" (0.760mm) restrictor just incase. But i dont want to use it unless i absolutely have to, as i dont want to starve the bearings of lubricating (and CHRA cooling) oil any more than i have to. And 0.030" may be just a bit too low.

My oil pressure is really high in this config. Peak oil pressure remains the same at about 6-6.5 bar (standard). BUT I am seeing oil pressures of 4.5bar to 5bar with the engine at 80+ °c at idle. I cant remember what it was previous, but it was alot lower. Like half that? usually around 1.5bar to 2bar i think if i remember right? The only thing i can put it down to is the ridiculously large oil filter i have hanging off the side of the car. Its like 5x times as big as a standard subaru oil filter. Or maybe the oil im using. I have switched to a motul 5w50 away from the penrite 10/tenths. Dunno. But that higher oil pressure could be over oiling the turbo. Garrett recomend 40-45psi (3bar) for the ball bearing GT/GTX turbos. Now i cant actually measure the oil pressure after the restrictor, but i can only assume the 0.035" restrictor is a better match to my oil pressure and oil wieght and the oil flow through the turbos bearing cartridge.

The other thing that i think was causing me turbo oil drain issues was the trouble with the solenoid valve that feeds the accusump. It was bleeding back after engine shutdown. And that would probably cause me problems if its bleeding back with the scavenge pump off. It prob holds 1.5L of oil, and even of only 10% of it bled into the turbo, even that amount could cause the mini sump to be a bit fuller than it should and cause the back up when i next started it. So for todays testing, i did not open the solenoid up to engine pressure. Meaning it will have no oil to bleed back after shutdown. I am still on the hunt for a better solenoid valve. Neil sent me through a picture of a part number he suggested to use. But i havent had any luck in locating it yet.

Another thing i did change is slightly re adjust the clocking angle of the CHRA. Trying to get a more verticle angle out of the drain. I only adjusted it maybe 5°. And i also adjusted the front to back turbo axis angle. Garrett recomend no more than 15° away from horizontal. And the way i had it setup, it was closer to 20° with the turbine side down. I adjusted it as much as i could without having to re-fabricate my pipework. So its now sitting right on the 15° limit recommended by Garrett. And thats still on jack stands, which have the front marginally higher than the rear. Once i get it back on 4 wheels, that angle should reduce a little less than 15°.

So i think all these changes have helped. I guess the real test will be once its actually driving. Right now im doing all the tests in the garage.

If it still is an issue. I will be freeing up the drain fitting. I checked my spare one today and its an AN10 to Garrett style flange. But its inside diameter is a pathetic 12mm. The actual hole coming out the turbo is about 5/8" (~16mm) i think. So that could be a potential bottleneck out of the turbo. Did some googling and Apperently those AN10 style adapters cause alot of turbo drain issues. AN10 hose should be 5/8 ID. But the fittings are actually smaller ID. And i am using 2 x adapers and a weld fitting into my little mini sump i built. So those tighter IDs could be another area to improve on.

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