T25 rebuild fiasco. halp!!
#1
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OK, so first and foremost I'll say that I'm a ******* IDIOT.
I set out to rebuild my SR20 T25. Got the compressor housings and turbine housings off without incident and then proceeded to snap then end of the turbine shaft off because I NEGLECTED TO READ THAT IT'S REVERSE THREADED. ~facepalm~
So now I need a new exhaust wheel/shaft, and hope I don't get raped for one because having to spend an absurd amount of money on a crappy T25 is just ridiculous.
So...where would be the best place to get a new shaft? A used one is fine too if anyone has one laying around. How many different sizes do they come in? Because I'm unsure of which one I have (I know the exhaust housing a/r is .64, even though that shouldn't have any bearing on wheel size).
Next question is about balancing. Once I put all this together supposedly the assembly needs to be balanced but I'm confused as to why this is necessary. If the compressor wheel is in balance from the factory, and the turbine wheel is in balance the same way, then why should they need to be balanced to each other? If something's in balance, then it's in balance. Regardless of whether a turbine, electric motor, fusion reactor, etc... is spinning it. Am I making sense here?
I set out to rebuild my SR20 T25. Got the compressor housings and turbine housings off without incident and then proceeded to snap then end of the turbine shaft off because I NEGLECTED TO READ THAT IT'S REVERSE THREADED. ~facepalm~
So now I need a new exhaust wheel/shaft, and hope I don't get raped for one because having to spend an absurd amount of money on a crappy T25 is just ridiculous.
So...where would be the best place to get a new shaft? A used one is fine too if anyone has one laying around. How many different sizes do they come in? Because I'm unsure of which one I have (I know the exhaust housing a/r is .64, even though that shouldn't have any bearing on wheel size).
Next question is about balancing. Once I put all this together supposedly the assembly needs to be balanced but I'm confused as to why this is necessary. If the compressor wheel is in balance from the factory, and the turbine wheel is in balance the same way, then why should they need to be balanced to each other? If something's in balance, then it's in balance. Regardless of whether a turbine, electric motor, fusion reactor, etc... is spinning it. Am I making sense here?
#3
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No expert on balancing ****, but here's my $0.02 on what I've seen.
Generally, you balance each part separately. Then you assemble and balance the assembly. Though in theory a bunch of balanced parts should remain balanced once assembled, it's not the case. On an engine for example, you might balance the PP, flywheel, and crank separately, but once assembled it needs to be rebalanced. This is partially because the PP isn't 100.000000000% centered on the flywheel, nor is the flywheel 100.00000000000000% centered on the crank. I would imagine the same is true on a turbo. When you assemble it, it's very close, but not perfect. And on a turbo, they spin.... kinda fast. So having something a little bit out of balance can cause a lot of problems.
But again, never rebuilt a turbo, or even had one apart. Good luck though.
Generally, you balance each part separately. Then you assemble and balance the assembly. Though in theory a bunch of balanced parts should remain balanced once assembled, it's not the case. On an engine for example, you might balance the PP, flywheel, and crank separately, but once assembled it needs to be rebalanced. This is partially because the PP isn't 100.000000000% centered on the flywheel, nor is the flywheel 100.00000000000000% centered on the crank. I would imagine the same is true on a turbo. When you assemble it, it's very close, but not perfect. And on a turbo, they spin.... kinda fast. So having something a little bit out of balance can cause a lot of problems.
But again, never rebuilt a turbo, or even had one apart. Good luck though.
#4
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I have an extra shaft and turbine wheel from another turbo. Not sure if they are the same size, i will have to measure it for you but i'm pretty sure its the same.
#6
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About the balancing, I didn't think about it when I rebuilt my turbo and now i'm kind of wondering myself. My guess is you wont hear it/feel it but I can definitely see how it would play hell on the bearings.
#9
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I can measure the SR20 cause I have one sitting 2 feet from me right now, although it might be easier for you to measure as I dont feel like taking mine apart again. Yea, measure yours lol.
About the balancing, I didn't think about it when I rebuilt my turbo and now i'm kind of wondering myself. My guess is you wont hear it/feel it but I can definitely see how it would play hell on the bearings.
About the balancing, I didn't think about it when I rebuilt my turbo and now i'm kind of wondering myself. My guess is you wont hear it/feel it but I can definitely see how it would play hell on the bearings.
#10
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I'll measure my wheel tomorrow too. I dont think you should need to measure the inducer/exducer, just measure the diameter as well as you can around the shaft
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Edit, no need to measure for you to measure:
Turbine: T-25, 62 trim 53.8mm 0.64 A/R turbine housing.
#14
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No expert on balancing ****, but here's my $0.02 on what I've seen.
Generally, you balance each part separately. Then you assemble and balance the assembly. Though in theory a bunch of balanced parts should remain balanced once assembled, it's not the case. On an engine for example, you might balance the PP, flywheel, and crank separately, but once assembled it needs to be rebalanced. This is partially because the PP isn't 100.000000000% centered on the flywheel, nor is the flywheel 100.00000000000000% centered on the crank. I would imagine the same is true on a turbo. When you assemble it, it's very close, but not perfect. And on a turbo, they spin.... kinda fast. So having something a little bit out of balance can cause a lot of problems.
though.
Generally, you balance each part separately. Then you assemble and balance the assembly. Though in theory a bunch of balanced parts should remain balanced once assembled, it's not the case. On an engine for example, you might balance the PP, flywheel, and crank separately, but once assembled it needs to be rebalanced. This is partially because the PP isn't 100.000000000% centered on the flywheel, nor is the flywheel 100.00000000000000% centered on the crank. I would imagine the same is true on a turbo. When you assemble it, it's very close, but not perfect. And on a turbo, they spin.... kinda fast. So having something a little bit out of balance can cause a lot of problems.
though.
#17
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directions fail
good luck with rebuild.
For the relative diameter and weight of the wheels compared to the shaft, I would imagine balancing isn't super-critical. It would be nice, but it's not like a flywheel that is around 20lbs, with a lot of that weight nearly a foot from the center of rotation.
good luck with rebuild.
For the relative diameter and weight of the wheels compared to the shaft, I would imagine balancing isn't super-critical. It would be nice, but it's not like a flywheel that is around 20lbs, with a lot of that weight nearly a foot from the center of rotation.
#18
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directions fail
good luck with rebuild.
For the relative diameter and weight of the wheels compared to the shaft, I would imagine balancing isn't super-critical. It would be nice, but it's not like a flywheel that is around 20lbs, with a lot of that weight nearly a foot from the center of rotation.
good luck with rebuild.
For the relative diameter and weight of the wheels compared to the shaft, I would imagine balancing isn't super-critical. It would be nice, but it's not like a flywheel that is around 20lbs, with a lot of that weight nearly a foot from the center of rotation.
All production turbos are balanced from the factory after the wheels are fitted. Hint hint. Do it right, or do it twice. You're already redoing it, do you really wanna cut another corner and chance doing this a 3rd time? Have a thousand dollar T25...
#19
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Getting the rest of the CHRA apart was simple, but I will follow the directions very carefully now when putting the new parts in.
#20
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Ok it gets better. I figured I'd continue to work on the center housing while I figure out my turbine shaft problem. I go to insert the radial bearing into the turbine side. No go. It's getting stuck on some washer. So i remove the washer. Which essentially means breaking it into pieces because it's not split at all. I'm not talking about the weird retaining ring that holds the bearing in. i had no trouble with that. Apparently it's an oil deflector of some sort according to part explosions I've seen.
Here's a pic from Samnavy's thread.
![](https://www.miataturbo.net/forum/attachments/2323d1161058531-rotating-assembly2.jpg)
That washer that's hanging loosely on the shaft there. That kinda looks like it. How was I supposed to get it out and more importantly, if I find a replacement. How does the new one go in?
Here's a pic from Samnavy's thread.
![](https://www.miataturbo.net/forum/attachments/2323d1161058531-rotating-assembly2.jpg)
That washer that's hanging loosely on the shaft there. That kinda looks like it. How was I supposed to get it out and more importantly, if I find a replacement. How does the new one go in?