Blowing smoke on deceleration after boost
 

I drove my car for the first time today since finishing my turbo build, it is blowing a lot of white smoke on deceleration after a pull in boost. It also blows a small puff of smoke on shifts. I searched and cannot find a definitive solution. Help will be greatly appreciated!

Build Info
-NA8
-MS3x
-ID1000
-ARTech manifold, downpipe, and exhaust
-used SR20 turbo from zilvia (Garret 2560 journal bearing), no restrictor (see pictures below)
-turbo supply line = -4AN, turbo drain line = -10AN (see pictures below)
-OEM PCV with line to intake manifold on cold side of valve cover, vented to atmosphere on hot side of valve cover (I will be getting a catch can setup soon)

Main Points
-a lot of white oil smoke comes out of the tailpipe for a few seconds after a few seconds of pulling with boost (6psi max). No boost = no noticeable smoke on deceleration
-according to a friend, there is also a small puff of smoke on shifts with no boost
-no smoke during the pull
-no smoke when revving without load (I held a steady 3000RPM for well over 5 seconds in a parking lot while watching the tailpipe and there was no smoke at any point) Sometimes it smokes a lot when idling, other times it does not
-this car did not smoke, burn coolant, or burn oil before this build. I did not open the engine during the build
-turbo was bought used from zilvia, it does not have excessive shaft play and looks like it is in really good condition (but I still think this is a turbo problem in some way, maybe turbo drain?)
-there is no oil in the compressor inlet, there is no oil in the charge piping or intercooler, all of those areas are completely dry

Do I need a restrictor even though this is a journal bearing turbo? Does my oil drain line stay horizontal for too long? I am not sure where to go from here because from what I have read when other people (on this forum and others) post about similar issues, they always have more symptoms. They smoke during the pull, or while revving, or there is oil in the charge piping.

Pictures of my turbo's oil inlet and drain line. Any suggestions would be greatly appreciated!

Seals on the turbo ok? Turbo housing all good? I suopose if oil was getting into it the smoke would be blue-ish. Anyway my first thought was the turbo itself and its state of health

Seals on the turbo ok? Turbo housing all good? I suopose if oil was getting into it the smoke would be blue-ish. Anyway my first thought was the turbo itself and its state of health.

I bought the turbo used and did not take it apart before installing it, so it is possible that the seals are bad. If the seals were bad, wouldn't there be smoke all the time and during acceleration in boost (not just on deceleration after boost)?

I had almost the same problem when my headgasket was leaking. After boost pull when the RPM drops on its own without braking to a certain RPM lots a smoke. With normal driving not, only when boosting

Could very well be the restrictor. It is a must on Garrett turbos.

The only issue with that I see with headgasket is that I do not have any of the symptoms that generally come with headgasket failure.

Even on journal bearing turbos? Instinct tells me that it would be better to rule out everything else before restricting oil to the turbo.

Yup. Read about it. My T25 is journal and I use a restrictor. I searched around before buying and the Nissan guys said you need it.

According to Garret a restrictor is generally not needed on journal bearings turbos........

https://www.turbobygarrett.com/turbo...oil_restrictor

It later says it is a good practice for a non rebuilt journal turbo. Most are at least 20 years old by now. The nissan turbos were fitted with one from the factory and a 10$ part couldn't hurt.

That is what I found as well.

I am leaning towards piston ring blow-by in boost, then on deceleration when the intake manifold goes into vacuum the oily air in the now pressurized crankcase is sucked in to the combustion chamber and goes out the exhaust. I am going to check compression and do a leak down test. Any thoughts on that theory?

That is another part of the problem. I bought this turbo used and have no clue what it has been through. However, if it were turbo seals I would expect a couple of things:

1. I would expect to see smoke at times other than only when decelerating. There is literally no smoke at any time except for when I come off of the throttle after being on it.

2. I would expect to see oil at the compressor inlet, or in the charge piping, or in the exhaust. There is no oil at any of those locations. That makes me think the oil that is making it out the exhaust is oil vapor (as it would be if it had gone through the combustion chamber).

Overrun conditions can suck oil around the rings and where I generally see oil smoke first on tired engines.

I have 0 experience with this. How much smoke would you expect to see in a situation like mine (if it is rings)? After a sustained pull in boost (even at just a few psi), there is a period of 2-3 seconds where there is a lot of smoke. Like enough smoke that if it were coming from under the engine I would be confident that my car were on fire.

In my car I know for sure the rings are toast. I see big clouds of blue smoke and I have a quart of oil per 800 miles consumption.
Keep an eye on your oil consumption. If it's not a big deal I wouldn't give it a second thought.

I am going to try a few things, but if it does not stop I am going to drive it until it goes for real. Then it will be VVT time.

I had an old small block Chevy that was beyond wore out, as a trick I'd run it up to 6k RPM and then let it coast down to 4k. It would haze smoke doing this but when I'd jump back on the gas at 4k I could cover 4 lanes of highway in smoke thick enough you'd think I blew the motor.

Every motor is different, compression and leak down numbers will tell you how bad it is.

That's the Miataturbo.net spirit :)

I hope mine does not get to that point once I start turning the boost up!