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Turbo - How Much Play Is OK?

I have a slight amount of lateral play on the air intake side of my stock turbocharger. I know there is some room for heat expansion in the bearings.

How much play is allowed? I'll measure tonight.

Who rebuilds turbos? Is it a DIY project (can you get parts)?


Thanks,
Mark
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1991 964 Polar Silver Metallic Turbo Coupe
Old 10-03-2008, 03:05 PM
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You can get the parts. But the turbo can spin more than 100,000 RPM which brings the DYI topic. After the center section is spec'd and reassembled as long as all is well, the turbine shaft/ impeller and compressor impeller HAS to be balanced. Other wise the shaft will wipe out the whole turbo.
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Old 10-03-2008, 03:17 PM
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I have a stock turbocharger. Does this one have ball bearings or sleeve bearings?

What is the average cost for a shop to rebuild the turbo assuming no mechanical damage other than normal wear?




Thanks,
Mark
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1991 964 Polar Silver Metallic Turbo Coupe
Old 10-03-2008, 05:32 PM
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Max radial end play: .026 in.
Max lateral end play: .014 in.

Source: Bentley 964 Technical Data
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Paul B.
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Old 10-03-2008, 05:36 PM
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That's a KKK...and Kevin at Imagine Auto is your expert in this field since he routinely rebuilds them...but I belive the KKK's use sleeve bushings...not ball bearings. The Garrett's are ball bearing.
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Old 10-03-2008, 10:56 PM
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Kevin is at Ultimate Motor Works up in Wash state. He supplies IA with the turbos. Great guy and really knows his stuff.
Old 10-04-2008, 02:28 AM
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Does turbo smoke/uses oil? Is there damage on blades? Does blades touch the housing? If all answers are no, I don't see the reason for rebuilding the turbo. There is always some play, even with new turbo. Personally, I'm against rebuilding unless it's a fraction of a price for a new one. Once bearing goes bad, it usually burns the shaft and/or blades touch the housing. In such case, it's probably better to purchase new one.
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Old 10-04-2008, 10:00 AM
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I started to replace the turbo mounting bolts since the engine is out and I just couldn't stop. So the turbo came apart and this is what I found:


I think the rotor shaft is OK, but the seals are toasted and the exhaust rotor looks a little rough:


I was looking on Ebay and there are some K27-7200 rebuild kits. One guy charges a little more but offers to balance the rotating assembly free of charge if you buy his kit. Any experience out there doing that kind of rebuild?

Thanks,
Mark
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Old 10-04-2008, 02:40 PM
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The major on the turbine is gone, you'll need a new turbine to rebuild that turbo. No reputable shop will rebuild that turbo with that turbine like that and if you do yourself, it's going to spool horrendously and won't last long. Sorry
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Old 10-04-2008, 06:09 PM
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Adam,
Thanks for the points you made, that's what I was thinking too. Funny, it ran pretty good prior to tear down...

I wrote to Kevin at Ultimate Motor Werks, he does not sell any parts and he just wanted to sell me a rebuild or a whole new turbo, he did not answer any of my questions.

I have not found a parts source for the exhaust turbine wheel, I am going to call Ron at Ron's Turbo on Monday morning. He will balance the rotating assembly for me. I'm also going to ask him for an exploded drawing of the K27-7200, so I can put it back together correctly.

Do you think this is typical at 62K miles?

Thanks,
Mark
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Old 10-05-2008, 04:24 AM
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Something............... Came from the motor and out the exhaust and it wasn't very small! I would do a leakdown test before anything else. What do the housings look like where the turbine impeller and compressor impeller are located?
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Old 10-05-2008, 04:40 AM
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Quote:
Originally Posted by lucittm View Post
I started to replace the turbo mounting bolts since the engine is out and I just couldn't stop. So the turbo came apart and this is what I found:


I think the rotor shaft is OK, but the seals are toasted and the exhaust rotor looks a little rough:


I was looking on Ebay and there are some K27-7200 rebuild kits. One guy charges a little more but offers to balance the rotating assembly free of charge if you buy his kit. Any experience out there doing that kind of rebuild?

Thanks,
Mark
Did you recently put new headers on the car? If true, it could be the weld slag from the headers came off and did a job on the turbine.
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Old 10-05-2008, 07:21 AM
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Quote:
Originally Posted by lucittm View Post
Adam,
Thanks for the points you made, that's what I was thinking too. Funny, it ran pretty good prior to tear down...

I wrote to Kevin at Ultimate Motor Werks, he does not sell any parts and he just wanted to sell me a rebuild or a whole new turbo, he did not answer any of my questions.

I have not found a parts source for the exhaust turbine wheel, I am going to call Ron at Ron's Turbo on Monday morning. He will balance the rotating assembly for me. I'm also going to ask him for an exploded drawing of the K27-7200, so I can put it back together correctly.

Do you think this is typical at 62K miles?

Thanks,
Mark

Mark, here's a picture of a clipped s3 wheel from a Turbonetics unit.



If you look at the major(area closes to shaft) you'll see the extended tips. These are what "protrude" into the volute of the turbine housing to help direct exhaust flow into the exducer(small diameter portion of the wheel leading to DP or exhaust)

That's what's missing from your turbine, and as others have mentioned, likely occurred from some form of particle impact. Could be piece of internal components(valves, rings, piston etc), very large carbon dislodge, or welding particulate/slag breaking free from inside the headers. However it can alos be a result from useage of Antilag or very late timing where EGT's get dangerously hot and melt components. Typical turbine wheel rating temp at speed is about 1800F
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Last edited by BoxxerSix; 10-05-2008 at 08:55 AM..
Old 10-05-2008, 08:52 AM
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"Carbon", very good point.
I have wondered about people putting SeaFoam in their tanks and if something like this could happen.
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Old 10-05-2008, 09:08 AM
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What others said. That's typical FOD damage. While it's possible for hi-mileage diesel turbos to be eaten away over years trough high sulphur content in fuel, it's not something that happens to low mileage gasoline driven cars.

You might want to do a leakdown test to ensure that it wasn't a piece of exhaust valve that went down into turbocharger. Either that, or a welding piece that dislodged from the presumed aftermarket header.

Also, inspect turbine housing for damage. If there is a damage on turbine housing, I would recommend changing the turbo as a whole and not trying to rebuild it. Changing the turbine wheel alone is tricky business that requires pricey balancing equipment, and if there are gauges on turbine housing the end result is most probably not going to be worth it.

Regards,
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Old 10-05-2008, 09:23 AM
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Quote:
Originally Posted by WERK-I View Post
"Carbon", very good point.
I have wondered about people putting SeaFoam in their tanks and if something like this could happen.

Seafoam does a really good job at dissolving carbon, and I suppose that if you had intake valves that were coated bad enough the SF could dissolve enough of the carbon at a time to dislodge a big piece into the chambers and out the exhaust that could do turbine damage, as you put that stuff in through PCV + vacuum lines while the motor is running.

If it was carbon it most likely came from a valve face. Valves are subjected to that high frequency slaping shock at RPM's that can break carbon off. I've seen this happen alot where guys will pour Marvel Mystery oil into the chambers/intake on an engine that been sitting awhile. MM has that same effect on softening/dissolving carbon.

Definitely agree with Goran on doing a LD and comp test on the motor just to get some info on the core of the motor. Might be more damage that's not readily apparent here.
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Old 10-05-2008, 09:30 AM
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WERK-I,
Stock exhaust that appears to never have been removed. So I rule out slag from the welds on the exhaust piping. Pistons are clean on top and I saw a normal amount of soft fluffy carbon in the exhaust ports of the heads.

Here are some shots of the inside of the turbo housing:



These are clearer, but the first one gives perspective:





It is interesting how the "major" part of the fins are bent forward. I'm thinking the damage caused them to wear thin then the heat and rotation bent the thin part.



Thanks,
Mark
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Old 10-05-2008, 09:33 AM
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Mark, the housing is surprisingly clean. The lack of damage to the inside radius of the housing and exducer on the turbine itself shows that it was either soft debris damage(carbon) or tune related(high egts in the manifold, "afterburn" related) Couple questions.....

1) You sure this is the original Turbocharger from the car?

2) How is the tune on the car? Sure the ignition timing is right on?

I mean you're missing a substantial amount of material from the major, probably a good 1/4" off each bucket in the deepest areas.
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Old 10-05-2008, 09:47 AM
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The third post in this thread contains a picture of the nameplate. I believe this is the original turbo for this car assembled in December 1990; although I cannot prove it. Maybe someone can weigh in with a definition of the nameplate data.

You are seeing the housing after I cleaned it in a very expensive and rare petroleum solvent - gasoline.

The ignition timing is good but I did have a stuck waste gate caused by an improper diaphragm (pinched) installation of an Andial 1.1 bar spring. The PO was a lead-foot (motorcycle racer) and he had the stronger spring installed.

I replaced the stock spring and the waste gate diaphragm during this rebuild. It will be nice to have a completely functional turbo.

If I could just find a source for the exhaust turbine wheel...

Thanks,
Mark
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Old 10-05-2008, 10:47 AM
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http://www.turbointernational.com They should be able to source the part required. I used to rebuild these things but now strictly deal with Garrett only, otherwise I'd get one for you.
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Old 10-05-2008, 11:06 AM
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