EPIC nuts/studs loosening thread (reposting stupid stuff without reading = warning) - Page 21 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-23-2009, 03:19 PM   #401
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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.
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Old 07-23-2009, 03:23 PM   #402
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Quote:
Originally Posted by TravisR View Post
How much does the assembly weigh? 50 lbs? At 1 foot from the head? Seems like a couple triangles could get that figured out...
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.
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What temperature do those studs get to anyways?
Nearing EGT I suppose if you run hard and long as they protrude in the MF.
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Old 07-23-2009, 03:23 PM   #403
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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.

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Originally Posted by TravisR View Post
There is another solution I had not thought of until just now. Use a longer bolt with a large spacer. This will effectively increase the distance the bolt stretches per tensile load. So with the longer bolt/stud you get more allowable stretch from a fixed amount of thermal expansion. Short fat bolts/studs are the worst with thermal expansion because the joint is so tight.
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.
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Old 07-23-2009, 03:29 PM   #404
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Originally Posted by Spookyfish View Post
@Hustler: forget grade 8, please get stainless 304L studs. Im having made a few sets (M10x1.5 and M8x1.25) and may have some sets left to send out for testing in 2/3 weeks.

To all others: we're stretching studs due to wrong material.
Well put.

Quote:
Originally Posted by TravisR View Post
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.
A half inch might be pushing it. But, maybe yeah.
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Old 07-23-2009, 03:32 PM   #405
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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.
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Old 07-23-2009, 03:41 PM   #406
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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.
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Old 07-23-2009, 03:44 PM   #407
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Originally Posted by TravisR View Post
I have to get back to projects, and the COP systems
4sure, get my COPs together mate!
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Just from a face run. at 1200 degrees the rod would stretch an additional .006 inches to accomodate the temp, which is ALOT
What variables involved? What changes if bottom mount or 45* up?
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Old 07-23-2009, 03:47 PM   #408
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Quote:
Originally Posted by TravisR View Post
I actually went back and read the entire thread. The damage is definitely from over expanding the joint.
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.
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Old 07-23-2009, 03:47 PM   #409
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Originally Posted by Savington View Post
In the last 100 posts there are more new ideas to solve this problem than I've heard about in the last year.
Win indeed, but we need to identify the problem, THEN become creative. Looks like it's the other way round sometimes.
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Old 07-23-2009, 04:02 PM   #410
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Quote:
Originally Posted by ZX-Tex View Post
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.
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.
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Old 07-23-2009, 04:04 PM   #411
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I still think Nitinol (shape memory superelastic alloy) deserves a role here.
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Old 07-23-2009, 04:14 PM   #412
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Originally Posted by y8s View Post
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.
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Old 07-23-2009, 04:31 PM   #413
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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.
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Old 07-23-2009, 05:11 PM   #414
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Originally Posted by Stein View Post
I have that option, too as my flange is tapped through. I could always drill out the threads.
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.
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Old 07-23-2009, 05:34 PM   #415
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Originally Posted by ZX-Tex View Post
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.
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Old 07-23-2009, 05:57 PM   #416
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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.
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Old 07-23-2009, 05:58 PM   #417
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Quote:
Originally Posted by ZX-Tex View Post
The problem is there is no good way to get the 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.
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Old 07-23-2009, 06:03 PM   #418
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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.
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Old 07-23-2009, 06:10 PM   #419
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Quote:
Originally Posted by ZX-Tex View Post
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.
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.
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Old 07-23-2009, 06:23 PM   #420
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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?
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