Fudged up my turbo rebuild...

Duder said:

Too much thrust play could certainly cause a compressor side leak.

I know I've said this before here but it's worth repeating: the piston rings are *gas* seals, as in air and exhaust gas. They prevent blow-by and leakage of boost and exhaust gas into the center housing. They are not, and cannot act as liquid oil seals. The difference in gas pressure across the piston ring is what keeps liquid oil from leaking out while running. When the engine is under load and in boost, there should always be positive pressure inward into the turbo's center housing, on both sides.
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Interesting. I always assumed they acted like oil rings on a piston. How does that explain oil not leaking when idling or heavy decel? There is no positive pressure on the compressor side then, or am I missing something?

Garrett (sample link) does talk about the pressure differential, however it also says this:

"At the turbine end, the sealing system is simple. After the oil has finished its work in the bearings, it travels along the shaft until it reaches the hub, where the spinning oil thrower literally throws the oil outwards by centrifugal force and it meets the inside face of the center housing where it drops down under gravity to be collected by the oil drain and returned to the engine sump. In addition to that, one or two piston rings are used which fit into a very accurately machined “stepped bore”. Unlike the piston rings inside the engine cylinders, these piston rings do not move. During the assembly process, the piston rings are compressed and once they are correctly located, the piston ring never changes position."

the video that he used it looks like piece #8 goes the other way. I know cause I made a mistake once, but took it back apart before I installed it. I flipped it like it should and everything went together smoothly. Im just saying Id take it all apart and start over.

I had an issue with a rebuild/compressor change out. The new compressor wheel assembled and torqued to spec, and it still had in/out play. Probably close to .2, maybe .4mm of play. Ran it and it immediately smoked. Removed it, disassembled and heated the compressor wheel for 10 minutes at 350f in the oven. Cleaned and froze the mostly assembled chra. Plopped the hot compressor over the frozen shaft, dropped the nut on and snugged to spec. Let it cool/normalize and checked the torque. No more in/out play at all.

lookforjoe said:

Interesting. I always assumed they acted like oil rings on a piston. How does that explain oil not leaking when idling or heavy decel? There is no positive pressure on the compressor side then, or am I missing something?

Garrett (sample link) does talk about the pressure differential, however it also says this:

"At the turbine end, the sealing system is simple. After the oil has finished its work in the bearings, it travels along the shaft until it reaches the hub, where the spinning oil thrower literally throws the oil outwards by centrifugal force and it meets the inside face of the center housing where it drops down under gravity to be collected by the oil drain and returned to the engine sump. In addition to that, one or two piston rings are used which fit into a very accurately machined ?stepped bore?. Unlike the piston rings inside the engine cylinders, these piston rings do not move. During the assembly process, the piston rings are compressed and once they are correctly located, the piston ring never changes position."

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I hadn't seen that sealing article yet, looks like we got someone other than marketing people to write it! It's a pretty good explanation of what's going on.

The oil seal is not a single part but rather a system. It's a labyrinth type arrangement between the bearing and the piston ring, with the goal of blocking or slinging as much oil away as possible. The way to get oil to not leak past a piston ring is to not have oil reach the ring. Keep it away, and keep a positive inward gas pressure differential.

Unless we're talking a draw-through carb turbo setup, the compressor is never really in much of a vacuum. Even when the engine itself and intake manifold is not in boost, the compressor is upstream of the throttle body and will almost always be at or above atmospheric pressure. At high engine speed / low load conditions like off-throttle coasting or engine braking, there will be higher airflow without boost, and a depression across the air filter can cause pressure in the compressor housing to go below atmospheric.

The key is the pressure differential matters. The interior of the turbo's center housing is at crankcase pressure, or very near it. With PCV you have vacuum in the crankcase due to it being linked to the intake manifold vacuum at idle or decel. As long as the center housing gas pressure is below the compressor housing pressure, you have air acting inwards on the piston ring, keeping the ring seated and helping to keep oil away from the ring on the inside.

Double piston rings in turbos can be used on either compressor end or turbine end or both. Sometimes there's even 3 rings on bigger units. All in the name of reducing gas blow-by, not for reducing oil leakage. Important to make that distinction.

Wow, there is certainly a lot more discussion on this thread than I anticipated. I've been busy with work lately, but I'm all for taking apart and reassembling. Thinking back, during the re assembly the compressor wheel was tight fitting on the shaft. I ended up freezing the turbine for a couple hours and then setting the wheel down. It did have some friction, maybe to much?

Duder, just to say, I always look forward to what you have to say regarding turbos and how they work. Way more info than I could ever find myself on google...its nice to know those "ring" type seals do not keep oil from passing, but that in/out travel of the turbine/compressor assembly could.

I am convinced that there is an issue with the rebuild. Whether it be the wheel not sitting down far enough because I did not heat the wheel, or maybe I did put the thrust washer or something backwards. Now the question is will I need a new rebuild kit? Could I clean, reassemble and have no in/out play? Or should I just bite the bullet and learn from my mistakes. The plan was to not have to touch the motor again, move on to brakes, suspension, etc... and now I'm buying dealer seals for the turbo side of the motor, so I really don't wanna have to pull it apart again.

A question I missed; no smoke out the exhaust during idle, cruise (no matter what rpm or speed) , or deceleration. The few times I initially laid into it, which was after the "recommended 150-200 miles on a rebuilt turbo" there was no smoke. Boosted fast, felt fast, felt smooth, I was stoked. Soon later, within the next 250-300 miles, there was lots of smoke under boost. I realized I was losing oil after that and began to not boost at all. And still lost tons of oil. Tore apart the drain and turbo and created more leaks doing that...

is your car your daily driver? If you wanted to send me the turbo I would be willing to look it over for you. NC. And reassemble, I have alot of extra turbo stuff laying around. Quesiton I have is, Where is your drain back to the engine. Block or oil pan? Maybe you answered that already. If so Im sorry. Ive seen people get the drain to low in oil pan. In fact my sons car I put it in the oil pan and if he is on incline or out of level. It will start smoking.

Yeah, it was my daily...not any longer lol. I've been super busy and this came up right in the middle of a career transition. I have yet to pull the turbo off, but it'll get a stock 16t in the future. I might be interested if I think it's over my head...but man, it's supposed to be easy.

Drain is in the original block spot, but a yoshifab press fitting installed with an AN coupler