Engine swap, now billowing smoke, do I need an oil restrictor?
 

Hi all, so I am using an ebay t3 50trim turbo. I have a 91 miata that was swapped to a 94-95 engine and only had what I considered to be a normal amount of oil build up in the charge pipes. Well, I just finished swapping it to a 96-97 engine now (didn't know that when I bought it) which means my oil feed line no longer comes from the port on the driver's side of the block, and instead had to be run around to the pass side and tee off the oil pressure sensor port. I drove it about 1 mile and had oil all over the front of the motor when I got home that I suspect came from the BOV, and it's making a ton of smoke out the exhaust. I'm using the same exact -4an feed line and -10an drain line I was using before without issue but I'm wondering if this new feed location is generating a lot more oil pressure than the old one. I'm seeing about 50-60 psi of oil pressure on the stock gauge w/ the 91 oil pressure sensor at idle. I never measured oil pressure off the old feed location. Thoughts or suggestions?

Why does nobody ever reply to my threads on this forum?

So I bought a Tee fitting and a .065 oil restrictor and used an old oil pressure gauge I had laying around to measure oil pressure after the restriction. It started at about 40 psi on cold start and then went down to about 17 after idling for a few minutes. Is this about where I want to be with a t3 journal bearing turbo? You can see in this picture oil literally started seaping from the exhaust side of the turbo, and a little sprayed out of the slight leak at my v-band connection. I'm guess the seals in my turbo must have gone bad from either sitting for a year without running, or from the few minutes I was using it without a restrictor perhaps the oil pressure was too high and caused the seals to blow?

https://www.miataturbo.net/attachmen...ine=1445128242

Yes, you probably crammed 1000x's more oil than you needed through that thing. This may or may not have pushed every seal out of the poor thing.

If you ran too much oil pressure and it caused oil to leak out the turbine, then that area is still covered in oil. Your restrictor may have fixed it, but now you gotta clean it or drive it a while to let the residual oil go away. My Garrett journal bearing used a seal like a piston ring, you're not going to "blow" it so I if yours is similar it's probably fixed now and the oil you see is what leaked out before.

Many reasons, but this can be good sometimes. Some threads 5 people will jump in and reply when they don't understand the problem, or the issue, or whatever and offer advice that isn't going to help. Best is reply when you can help, or at least have an idea of what's going on. My advice is limited since I've never run an ebay turbo for example, but I did run a .062 restrictor and 12an line on my Garrett without problem with 10w-30 oil.

because your threads suck

Well, I cannot for the life of me find my compression tester, it probably got loaned to a friend who then refuses to admit he still has it... I do have my leak down tester so I'm going to try to get that test done tonight.

Some back story: I was using this same exact turbo, same oil feed line, same oil drain line, and same oil pan on my 94-95 engine which received the oil feed from the port on the driver's side of block. That setup lasted several months without a restrictor and I never had smoke out the exhaust or an abnormal amount of oil buildup in the charge pipes. That engine started to get rod knock at an event, was towed home, and parked for a year. I bought a running 94 parts car which is what I pulled this engine out of and didn't realize it was a 96-97 engine until I went to screw in the oil feed and was like "um, where's the port?" Luckily my oil feed was long enough to reach around to the other side, I had the correct Tee fitting from a project a long time ago, and the local parts store had the 1/8 npt to -4an adapter I needed to Tee off the oil pressure sensor port. Does this port really flow that much more oil/oil pressure to overfeed the turbo vs. the driver's side port?

Also, does 17 PSI at idle sound about right for a journal bearing turbo? It'll probably drop even further once fully warmed up, this was only after idling for 3-4 minutes.

You're right, I only ever come on the forums when I'm having problems anymore :cry:

Cylinder leakdown test came back 4-5% leak on cyl 1, 2, and 4, and 8% on cyl 3. All 4 of which showed the small (acceptable) amount of leak to be coming from the exhaust valves, so I'm happy with the condition of the motor. I guess I'll try letting it run for a while and see if the smoke clears up, if it does then I guess I'm golden, if not, then I guess I'll be on to my third $175 ebay turbo... Perhaps this time around I'll get a 60 trim t3 instead of a 50 trim. I've been looking at compressor maps and it would appear that at 12 psi I'm riding the choke line of this turbo, and I was running it 15 psi :rofl: I'm thinking I'll be a little more conservative and shoot for ~11-12 psi this time around though to buy me more time to build my old rod-knocky motor. I'd fall in the 70% efficiency island of a 60 trim t3 @ 12 psi

I killed my GT3271 by running it at choke flow. I don't recommend it. Eventually the 270* steel thrust bearing wore out (that's hard to do) and the comp wheel hit the housing, rear oil seal failed.

The first turbo I ordered off ebay didn't list any specs besides the A/R size but it was supposed to be a t3, but instead I got shipped a 70 trim t3/t4, which I put on my 1.6 engine. It wouldn't even start building boost till 4500 and full boost around 5500 which still felt weak. That one lasted all of about 18 miles before I blew the oil seals in it. I bought my current t3 50 trim to replace it and I love the feeling of it, it spools really fast and pulls hard, but I don't want to be pushing it into territory it isn't able to handle. How poorly do ya think a t3/t4 42 trim would spool? Looks like it'd be right in the sweet spot on the compressor map. Here's the specs I'm looking at:

Compressor Wheel diameter: 50.16 / 76.84 (.426 trim)
Turbine Wheel diameter: 54.06 / 65.20 (.687 trim)

these are the specs on my current turbo

Compressor Wheel Ind: 42.42 / 60.20 (.497 trim)
Turbiner (the ad literally says "turbiner") Wheel 46.23 / 64.01 (.522 trim)

I have no idea how that turbo would spool. Just saying don't run one into choke flow and expect it to last! :)

when you stop dumping raw oil on the exhaust, i suspect the car will stop smoking.

Billowing smoke can be pretty.

The oil you see on the turbo/exhaust was not spilled there, it leaked out of the turbo and sprayed out of the slight leak at the v-band connection right after the turbo.

So I decided there was a real easy way to tell if the turbo was bad, I popped the intake off and felt the shaft play, it has a good 3-4mm of movement in all directions, don't know why I didn't think of that sooner... In any case, it looks like I'm turbo shopping again :beer: