EPIC nuts/studs loosening thread (reposting stupid stuff without reading = warning) - Page 29 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 08-07-2009, 06:33 PM   #561
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Originally Posted by y8s View Post
And the higher end shops use Inconel... can FR, AMS, and TiAL show their research and prove that one is better or do people just spend more money on shiny polished stainless?

When I got my manifold a brazilian years ago, I picked mild steel for two reasons: First, people I trusted suggested it would have better thermal cycling behavior compared to SS and Second, it was cheaper. I didn't give a rats *** if it was shiny.
You can be frivolous with your asses because they aren't shiny. I only get stainless steel rat's asses (a reference no one should get) because I believe in always purchasing the very finest.

Pic of mani?

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Originally Posted by sixshooter View Post
Travis,
The problem is with the expansion of the cast iron side of the connection, the turbine housing mounting flange. When using studs it doesn't matter if they are in an iron, stainless, mild, chrome moly, or titanium manifold because if the manifold expands and contracts, the studs aren't being stretched. The expansion that effects studs is in the turbine flange.
This, of course, only applies to studs and not to bolts. Bolts have the expansion of both the thickness of the turbine flange AND the thickness of the manifold flange to compensate for.
I think you're on 15 types of crack here. Sorry. :-) I'm not sure how what's on the end of a threaded shaft (a nut or a bolthead) will make much difference to how much the middle of the shaft gets stretched.

The bolts/studs ("fasteners") will also warm up, and expand, so there is no issue. It's differential expansion which hurts you
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Old 08-07-2009, 06:49 PM   #562
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Originally Posted by AbeFM View Post
You can be frivolous with your asses because they aren't shiny. I only get stainless steel rat's asses (a reference no one should get) because I believe in always purchasing the very finest.
so are you saying that stainless steel rats asses can handle higher DiGriz?

manifold w/ceramic coating. made from big fat weld els.
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Old 08-07-2009, 07:31 PM   #563
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I can report that after 2x 30min sessions my weldjob is still together and verified with street driving: no leaks, same spoolup, full boost.

That is 304-something studs and welding.
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Old 08-07-2009, 07:31 PM   #564
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Originally Posted by Spookyfish View Post
I can report that after 2x 30min sessions my weldjob is still together and verified with street driving: no leaks, same spoolup, full boost.

That is 304-something studs and welding.
Oh, and that was running faster than the spec miata track record.
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Old 08-07-2009, 07:38 PM   #565
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so are you saying that stainless steel rats asses can handle higher DiGriz?

manifold w/ceramic coating. made from big fat weld els.
Jesus. Out nerded.
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Old 08-07-2009, 08:12 PM   #566
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Originally Posted by TravisR View Post
3.) Stainless steels have no high heat strength properties. It mise well be butter when you warm it up.

+

Yea, but if it was made from mild steel which is half the cost of stainless, no one would have fastener pull out problems. PERIOD
I am calling BS on your metal doctor, or you - whoever came up with this.
We all have failing studs because use (mild) steel not stainless. Read up on THIS:
https://www.miataturbo.net/forum/t35874-20/#post433903

These guys run 304 and it works for them and they tell me normal steel will fail:
https://www.miataturbo.net/forum/t35874-9/#post424085

I do agree that Inconel is the win, but it is insanely expensive.
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Old 08-07-2009, 08:22 PM   #567
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Originally Posted by sixshooter View Post
The problem is with the expansion of the cast iron side of the connection, the turbine housing mounting flange.
No it is not. Corky has already found (see the corresponding thread on M.net) that the expansion rate is actually slightly smaller.
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Old 08-07-2009, 09:29 PM   #568
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Quote:
Originally Posted by AbeFM View Post

I think you're on 15 types of crack here. Sorry. :-) I'm not sure how what's on the end of a threaded shaft (a nut or a bolthead) will make much difference to how much the middle of the shaft gets stretched.

The bolts/studs ("fasteners") will also warm up, and expand, so there is no issue. It's differential expansion which hurts you


If you have a stud you only have to worry about the red area of thermal expansion. That is the iron only unless I am missing something. Please try to explain how the manifold material would matter if you were using studs.
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Old 08-07-2009, 09:44 PM   #569
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jesus. Out nerded.
:d
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Old 08-07-2009, 09:48 PM   #570
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Originally Posted by Spookyfish View Post
No it is not. Corky has already found (see the corresponding thread on M.net) that the expansion rate is actually slightly smaller.
Corky also "thinks" the studs are expanding. As far as I'm concerned, he doesn't have a clue when it comes to this problem.
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Old 08-07-2009, 10:48 PM   #571
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Originally Posted by Spookyfish View Post
Corky has already found (see the corresponding thread on M.net) that the expansion rate is actually slightly smaller.
Five minutes on Engineering ToolBox and I built the table below. Why is Corky such a genius for knowing this?

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Old 08-07-2009, 10:57 PM   #572
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Originally Posted by AbeFM View Post
Jesus. Out nerded.
No, bringing home Machinery's Handbook for a little light reading is FTW, I think.

Stainless Steel - High Temperature Resistance
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Old 08-07-2009, 11:59 PM   #573
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Originally Posted by SolarYellow510 View Post
Five minutes on Engineering ToolBox and I built the table below. Why is Corky such a genius for knowing this?

2 comments:

1. note regular steel expands like a quarter less than stainless steel
2. also note mild steel has a significantly better coefficient of heat transfer than stainless so it doesn't hold the heat the same way.
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Old 08-08-2009, 12:00 AM   #574
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Originally Posted by sixshooter View Post
If you have a stud you only have to worry about the red area of thermal expansion. That is the iron only unless I am missing something. Please try to explain how the manifold material would matter if you were using studs.
Are you assuming that the stud is seated in the manifold, or in the turbo?

Anyway, yeah, I think I was on the crack. Actually, I was too drunk to work and killing time at my desk so I was mouthing off on the forums. ;-)
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Old 08-08-2009, 12:11 AM   #575
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The fact that the red area is half the depth of the sum of the mani and turbo flanges suggests that the stud needs to have TWICE the CTE of the flange material in order to "keep up".

I think what happens is that because the stud is the same material, the flanges grow and stretch the stud past its plastic deformation limit, and the stud then stays stretched so it stays loose when it all cools back down.
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Old 08-08-2009, 01:15 AM   #576
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Old 08-08-2009, 02:07 AM   #577
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You ain't got **** yet, buddy, other than debt. And some useless crap.
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Old 08-08-2009, 02:09 AM   #578
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Once this thread reaches #900 posts I'll post something constructive.
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Old 08-08-2009, 05:06 AM   #579
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Quote:
Originally Posted by JasonC SBB View Post
The fact that the red area is half the depth of the sum of the mani and turbo flanges suggests that the stud needs to have TWICE the CTE of the flange material in order to "keep up".

I think what happens is that because the stud is the same material, the flanges grow and stretch the stud past its plastic deformation limit, and the stud then stays stretched so it stays loose when it all cools back down.
Studs grows more than flange in case of stainless studs. So non-issue.
Also, doesnt need twice the CTE is its got only half the material that is expanding.
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Old 08-08-2009, 05:50 AM   #580
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Can someone explain to me why the thermal expansion rate matters? The only measurement I can see that has any weight in the material decision would be yield strength. The studs are heated, which drops yield strength, and then they stretch (plastic deformation). I have proven that this is the problem. It isn't excessive thermal expansion which reduces the torque load, it's plastic deformation.

So if it's not stainless steel, what material do we get studs out of that can handle the stress?
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