T25 rebuild fiasco. halp!!
 

OK, so first and foremost I'll say that I'm a FUCKING 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 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.

No expert on balancing shit, 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.

Dude that would be freaking awesome. You measure yours and I'll measure mine. LOL.

:giggle:

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.

I did the same thing a couple months ago. I found someone who sells the wheel and shaft but it's 135....So I just bought a new turbo and said fuck it.

Man you guys fail at following directions lol.

How long have you been running it since the rebuild? I'll measure the wheel tomorrow.

Its not installed yet which is why i'm still not sure how severe the potential problems might be.

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 :giggle:

Edit, no need to measure for you to measure:

Turbine: T-25, 62 trim 53.8mm 0.64 A/R turbine housing.

They say to measure from the base... erm.... what I mean is, I'll measure from the base of the wheel where it's at it's largest diameter. :D

Measure from the base to the tip and add 3" and that is the size of your shaft

thats what she said:jerkit:

I'm worried about this exact thing. In samnavy's rebuild thread he doesn't mention balancing/marking any places, but I've heard other more m.net types say that an unbalanced turbo is sure death. I'd assume that sam's turbo didn't kill him, so it should be fine, although at a few hundred thousand rpm, I'm not sure if I'd want anything to be shaking around.

If an unbalanced turbo is sure death, my turbo would have failed multiple times, many years ago. hell i still made 200rwhp with a bent shaft :P

balancing is for pussies

If you had followed braineack's turbo rebuild tutorial you wouldn't have this problem :)

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.

Not a valid comparison. Forces go up exponentially with speed. And turbos spin fast, so even a very small imbalance can cause huge forces if it spins fast enough.

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...

I did. I had it printed out and in front of me at the time. I didn't bother reading it over during this step because I was like "Oh I know what to do here".

Getting the rest of the CHRA apart was simple, but I will follow the directions very carefully now when putting the new parts in.

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/att...-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?