GT2560R: Oil In Compressor Housing
 

I've been slowly putting together my turbo miata, and have finally mounted the turbo in the car. I bought a used GT2560r off ebay. The guy said he had it on a bike, and only did about 10 or so dyno pulls with it. When I got it, the thing looked brand new, no rust, no shaft play, pristine turbines, no carbon build up on the exhaust side. I have no reason to think the thing is bad.

I have the turbo installed with coolant, oil, and exhaust routed. I have yet to put the intercooler piping on, so the thing just pumps air into the atmosphere ;). My oil line setup is -4AN feed line coming from the high pressure port on the exhaust side of the block. That goes through a 1mm restrictor before feeding into the turbo. On the drain side, I have a 1/2" ID hose going directly into the pan (see photo for location). The oil ports on the turbo are clock perfectly vertical so gravity can do its work. The drain line has no uphill/snakey regions. I also drilled high enough on the pan so the port is above the oil level.

After I take the thing for a drive, I always find some oil blown out of the compressor outlet. It does this with the turbo spooling (wastegate held closed), and without (wastegate held open). For that reason it makes me think the oil pressure is too high. However, I took it for a drive and kept the oil pressure at a steady 30psi (monitoring the factory oil pressure gauge). 30psi is below the 40-45psi Garrett recommends, and yet it still blows oil out. I thought maybe crankcase pressures were too high, but I drove it with the breather hose disconnected, the dipstick out, and even the filler cap cracked... still blows oil out! :crx:

I haven't checked to see if its blowing oil out the exhaust seal too, but I do see some smoke come out of the wastegate arm port when the engine is shut off. Is that normal?

I'm running out of ideas. Could it be because I don't have the intercooler piping on and it's not actually building boost, so could boost pressures help keep the oil from leaking out? Has anyone ever put a oil pressure gauge on their turbo to measure the pressure after the restrictor?

Could any of the orings be bad? I don't think their job is to keep oil inside the CHRA anyway...

I'm running 10W-30 Mobil One if that means anything.

https://cimg2.ibsrv.net/gimg/www.mia...190bb1877c.jpg
Note: This photo was taken when I had a 3/8" ID drain hose. Now I have 1/2" ID

UPDATE!

I wanted to respond just in case someone else is running into the same problem I did.
It turns out the turbo is FINE! I put charge piping on the car, and it seems like once the turbo has some resistance and is building boost, the oil leak stops. I couldn't believe that the problem went away lol. I'm now happily building 10psi of boost!!!! :D

You were likely overspeeding the turbo with no resistance on the compressor side.

And BB turbos need a restrictor. They require little oil.

And you need better oil, IMO.

What oil do you recommend? My engine has 210,000 miles on it

Rotella T6 Synthetic, available in gallon jugs at Walmart and elsewhere.

I hear Rotella has changed their specs. It's not the same at all.

I hear it's the same.

Also, running a turbo with the compressor section venting to atm. is a very simple way to destroy your turbo, genuine BB Garrett or otherwise.

You are correct. But Rotella T6 still has a much, much better additive package and film strength than Mobil1 10w-30. If he was doing trackdays only I would suggest something else entirely but it wouldn't be a good daily driver/street turbo oil. Race oils don't need anti-acid and detergent additives in the same way as a street car (extended change interval).

I thought I'd read somewhere that we should stay away and use AMSOIL 5W40 synth instead as the additive packages were more in tune with our turbo'd engines.
But I may be wrong, and the guy that wrote it may be off his rocker. He seemed knowledgeable on the subject... More research is needed.

https://forums.nasioc.com/forums/sho....php?t=2785176

see thread

EDIT: NVM - https://www.miataturbo.net/engine-pe...s-88691/page4/

Better thread here.... Already discussed. Apologies..... Here is my cat exploring his options.