EPIC nuts/studs loosening thread (reposting stupid stuff without reading = warning)
#1041
Elite Member
iTrader: (15)
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,847
Total Cats: 27
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Yeah I can see that. Series of events: WOT with high turbo RPM -> throttle off (drastic flow reduction) but turbine still spinning due to rotational inertia -> turbine creates upstream vacuum (until it spins down or throttle is reopened).
#1042
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
My first attempt looked something like this. It cracked at the weld to the flange as did a few other manifolds I had seen of similar geometry. My reasoning was the difference in thickness between the flange material and the exhaust tubing. The uneven distribution of thermal mass caused the flange and the pipes to heat and cool at different rates thus they can be at different temperatures for short instances. This causes a huge stress concentration at the interface between the two different thicknesses of material.
I will post a picture of mine
Bob
I will post a picture of mine
Bob
#1043
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Here is a picture of what I did. The studs holes are countersunk well into the welded on round bar stock that multifunction as nuts for the studs, gussets for the flange, and transitional thermal mass to give a more even mass distribution up to the joint.
The diving board thing attached to my turbine outlet actually holds the turbo positioned up to the manifold flange even if all the studs are loose it is spring loaded a tad when everything is assembled. The first one made of mild steel cracked this one was made out of 4130 and has not cracked.
Bob
The diving board thing attached to my turbine outlet actually holds the turbo positioned up to the manifold flange even if all the studs are loose it is spring loaded a tad when everything is assembled. The first one made of mild steel cracked this one was made out of 4130 and has not cracked.
Bob
#1047
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Interesting that in that picture you show 8.8 studs. Just like the last set I had that stretched. Doesn’t matter what you do to keep them from turning if there still going to stretch, loose clamp. or fatigue crack like mine did after enough extreme heat cycles.
Bob
#1048
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
How much for the inconel studs? Do you guys have them? How long are they?
Interesting that in that picture you show 8.8 studs. Just like the last set I had that stretched. Doesn’t matter what you do to keep them from turning if there still going to stretch, loose clamp. or fatigue crack like mine did after enough extreme heat cycles.
Bob
Interesting that in that picture you show 8.8 studs. Just like the last set I had that stretched. Doesn’t matter what you do to keep them from turning if there still going to stretch, loose clamp. or fatigue crack like mine did after enough extreme heat cycles.
Bob
Are the threads on the Begi Inconel studs machined or rolled?
#1050
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
How much for the inconel studs? Do you guys have them? How long are they?
Interesting that in that picture you show 8.8 studs. Just like the last set I had that stretched. Doesn’t matter what you do to keep them from turning if there still going to stretch, loose clamp. or fatigue crack like mine did after enough extreme heat cycles.
Bob
Interesting that in that picture you show 8.8 studs. Just like the last set I had that stretched. Doesn’t matter what you do to keep them from turning if there still going to stretch, loose clamp. or fatigue crack like mine did after enough extreme heat cycles.
Bob
The inconel studs are $148.60 for a set of four. We do have them. They are 47 mm in OAL. If you do not need that length, they can be cut down some. They are so expensive because they are machined by hand. This grade of Inconel cannot be cut with a normal die. I will get them added to the website in a few!
Stephanie
#1051
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Here is a picture of what I did. The studs holes are countersunk well into the welded on round bar stock that multifunction as nuts for the studs, gussets for the flange, and transitional thermal mass to give a more even mass distribution up to the joint.
The diving board thing attached to my turbine outlet actually holds the turbo positioned up to the manifold flange even if all the studs are loose it is spring loaded a tad when everything is assembled. The first one made of mild steel cracked this one was made out of 4130 and has not cracked.
Bob
The diving board thing attached to my turbine outlet actually holds the turbo positioned up to the manifold flange even if all the studs are loose it is spring loaded a tad when everything is assembled. The first one made of mild steel cracked this one was made out of 4130 and has not cracked.
Bob
#1052
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
That picture was pre-inconel studs. And no, bolting the studs in won't do a darn thing if the stud is stretching.
The inconel studs are $148.60 for a set of four. We do have them. They are 47 mm in OAL. If you do not need that length, they can be cut down some. They are so expensive because they are machined by hand. This grade of Inconel cannot be cut with a normal die. I will get them added to the website in a few!
Stephanie
The inconel studs are $148.60 for a set of four. We do have them. They are 47 mm in OAL. If you do not need that length, they can be cut down some. They are so expensive because they are machined by hand. This grade of Inconel cannot be cut with a normal die. I will get them added to the website in a few!
Stephanie
I will be ordering a set in the next few weeks. I think the next time mine comes loose I will need to Helecoil because the threads get damaged some every time you take it apart after hard thermal abuse. I could put in the set screws as well.
Bob
#1053
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
The threads will get damaged with repeated install and uninstall. Taking a die to it, gently, will be OK.
Turbo Mounting Hardware - Inconel BEGi
Stephanie
Turbo Mounting Hardware - Inconel BEGi
Stephanie
#1056
Former Vendor
![](/mt2011/images_td/ranks/supporter1.gif)
iTrader: (31)
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,442
Total Cats: 2,103
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
https://www.miataturbo.net/group-buys-member-discounts-23/trackspeed-engineering-inconel-manifold-stud-kit-%24105-shipped-46091/#post554872
TSE inconel stud kit GB, $105 shipped.
TSE inconel stud kit GB, $105 shipped.
#1057
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
I noticed today while browsing M-Carr at work that they now carry high temp inconel Belleville washers (1100F). Not sure on the load ratings, but it seems the concern with using these washers in past discussions was their inability to retain their form at high heat.
#1058
Former Vendor
![](/mt2011/images_td/ranks/supporter1.gif)
iTrader: (31)
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,442
Total Cats: 2,103
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
We talked about it like ~600 posts ago, I think the consensus wasn't that heat was an issue, but just that they would bottom out once you put enough torque on the nut to actually seal them up. We'd need a stack of them to get enough clamp force and still have them be a little springy, and there's just not room for that on T25 flanged turbos.
#1059
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
We talked about it like ~600 posts ago, I think the consensus wasn't that heat was an issue, but just that they would bottom out once you put enough torque on the nut to actually seal them up. We'd need a stack of them to get enough clamp force and still have them be a little springy, and there's just not room for that on T25 flanged turbos.
oh well.
-zach
#1060
![Default](https://www.miataturbo.net/images/icons/icon1.gif)
Epic failure of the Dorman 10.9 studs. I was a little nervous when the box they came in said made in China. Day one at Laguna 3 out of 4 studs broke just under the nut. Surprisingly my little spring loaded turbo support keeps it from having a massive exhaust leak thankfully. Day 2 replaced all 4 studs with 4 new ones of the same kind 2 held one kept loosening and the third broke off.
Grade 8.8 definitely better than 10.9 for the turbo But still not acceptable.
Bob
Grade 8.8 definitely better than 10.9 for the turbo But still not acceptable.
Bob
Last edited by bbundy; 04-14-2010 at 01:22 AM.