I actually went back and read the entire thread. The damage is definitely from over expanding the joint.

Is there a spacer available for the T-3 flange? a half inch there, and a couple of standard teeth washers on the otherside of that flange would lengthen up the stud quite a bit and probably fix it for good. Then torque to 30-40 percent of maximum. Use grade 5 hardware so there is some flexibility in the hardware. Grade 8 is too hard.

The spacer would be better off made of ceramic or something along those lines so that it doesn't expand.

 

I suppose someone might find some interesting ideas. Turbo + DP, 1ft, how much g's lateral and longitudinal, blah, blah, blah. Then at least we can verify is M10 is enough in size, then we need to get the material right.
Nearing EGT I suppose if you run hard and long as they protrude in the MF.

 

I've seen stacked B-washers suggested before, and them written up to be used that way (I think it's Carrol Smith's book - though in the end he's always a fan of 1) get the right size/stregnth for the application, and 2) torque it right, so that you're well below yeild under the worst conditions. He's also a fan of "biting" lock washers, which is the same every single thing I've read out of NASA and MIL-specs agrees on. All forms of spring washers don't buy you much.

The large spacer idea would be good, EXCEPT: I can't even get a box end in there, it's so tight. I can't use just any old washer (when I was still using them) because it's too fat. So, if by "large spacer" you mean "something 1 or 2 threads tall" you might be onto something. :-)

The different coeff of expansion isn't a bad idea. Stacking B-washers might be the best, but I've yet to find any which hold up to temps. Really I think a big part of any answer is going to be design the turbo and collector to accommodate sensible fasteners. If you allow for big bolts, good washers, locking, etc, you might have a chance. 8mm bolts are just enough to hold it together when cold, and that gets back to the v-band thing.

I'm still curious about the 10mm-wired thing. Bracing might help - I used to lose fuel rails all the time because I'd removed the intake manifold brace, and the vibrations would kill ANYTHING I put on there. It's certainly not helping.

 

Well put.

A half inch might be pushing it. But, maybe yeah.

 

I have to get back to projects, and the COP systems, but if I have time I'll run the calculations the people who manufactured these units and are supposedly all powerful should have already ran. Just from a face run. at 1200 degrees the rod would stretch an additional .006 inches to accomodate the temp, which is ALOT. It may just not be even designed correctly enough to be functional.

 

This is a ******* awesome thread, BTW. In the last 100 posts there are more new ideas to solve this problem than I've heard about in the last year.

 

4sure, get my COPs together mate!
What variables involved? What changes if bottom mount or 45* up?

 

In that case I may effectively be testing this idea. Repeating myself here but since I have the S4 I am able to go to a through-bolted design instead of a stud. This effectively doubles the grip length of the fastener; the S4 flange is about the same thickness as the T2 flange on the Garrett. We will see if it works.

 

Win indeed, but we need to identify the problem, THEN become creative. Looks like it's the other way round sometimes.

 

I have that option, too as my flange is tapped through. I could always drill out the threads.

I don't have a lot of room on the backside, but on the turbo side, I could probably add 1/2" or maybe 1" of spacer under the bolt head to increase stud length.

One other option that I have is because my flange is tapped, I could use bolts through the turbo flange (with or without spacer under the head), threaded into and through the mani flange and then STILL run a locking nut on the backside of the mani flange onto the bolt that protrudes through, essentially "double nutting" it. That's what I have on my current studs. It would eliminate the extra nut/lock washer on the front side that I have now.

 

I still think Nitinol (shape memory superelastic alloy) deserves a role here.

 

Find me a car with Nitinol studs between turbo and manifold that stays alive on track. The only relevant Google hits are from miataturbo.net. Go figure.

 

While I think they might be interesting, I suspect they'd be prohibitively expensive compared to something else that will work. nitinol wire is 10 cents an inch.

 

Yeah that is what I did. A stepped-bit worked great though it did take some psyching up to drill out the threads on my shiny new S4 manifold. If you can wait you might want to see how mine works out first.

 

I'm thinking my next move is stainless bolts, through tubo threaded into flange with a backing nut and Resbond.

That's my low cost next step. My Holley carb studs worked for four months with regular old lock washers as supplied with the kit and never a retorque. This has to be better.

 

The problem is there is no good way to get two of the four bolts through the turbine flange, at least not on my turbo. The only way to do it I could see is to notch out the flange.

With the through-bolt, I can bring the bolts in from the S4 side, and put the nuts on the turbine side.

 

At OTS they have a threaded flange, studs in. Tack weld on MF side. Nuts on turbo side. The end.

 

Yes, that is basically how the S4 manifold works, minus the stud tack welding.

Two problems:
- One, it does not increase the grip length per the above discussion.
- Two, it is still a mega-PIA to tighten the nuts on the turbo side when it is in the car. With the through-bolt arrangement, all I need to do is get a wrench on the nut to hold it (not easy, but no rotation required) and then rotate the cap screw which will be easily accessible from above. Hell I will probably even be able to use a torque wrench on it.

 

I think that I can do it on mine. Three for sure. I need to check the fourth. Early installation pic. Worst case would be notching the lower right which is tougher to get at anyway. Install one bolt, slide on turbo, bolt the other three through, tighten all four.

 

I don't really meet all the requirements to post, but I'm gonna ask anyway...

about the only thing I can think of with the same orientation as a standard Miata cast set-up from the factory is a Dodge Cummings I just went and looked at one to verify, and they use a stud with a nut. if the studs on a Miata stretch you would think they would have the same issue, which I've never heard before. they run more boost and I would think the chipped ones see much higher EGT's than a track set-up especially towing. does anyone know the material they use for those studs?