EPIC nuts/studs loosening thread (reposting stupid stuff without reading = warning) - Page 23 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-24-2009, 03:59 PM   #441
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Here's what I found out. Every engine manufacturer uses studs. Today I looked at what we had on the yard, Cummins, Caterpillar/Perkins, Isuzu Heavy, Isuzu Medium, Mitsubishi Heavy, Detroit Diesel, Mercedes Heavy Diesel, Hino Heavy Industries, and Deutz Diesel. Some of these turbos weigh nearly a hundred pounds and are supported by four studs and nuts. No support bracketry or bracing for the weight of the turbo. Some turbos are hanging down from the manifolds, some are off of the side, and some bolt on top of the manifolds. ALL of them use studs. ALL of them use a raised stamped metal gasket between the manifold and the turbo. ALL of the ones that use a M10 by 1.5 size stud require around 33 to 38 ft. lbs nut torque and require the use of anti-seize compound on both sides of the stud. NONE of them leak or require re-torquing. BTW - they all use shouldered nuts and no washers (except the Isuzu Heavy uses a non-shouldered nut) .

I'm going to jump out here on a limb and say that there is a combination of things working here. 1. The right studs. 2. The "spring"effect of the raised stamped steel gasket taking up the extra squeeze that would normally stretch the studs, and the fact that the gasket's springiness could still seal when cool as well.

Here are some of the many pics I took. They are:
1. Cummins B-Series turbo stud and nut (M10 x 1.5) from our parts department. -obviously made of two different metals (obtanium creditus cardus and secondus mortgageous).
2. Raised stamped steel gasketfrom Cummins C-Series engine
3. Perkins/Caterpillar turbo setup
4. Closeup of Perkins/Cat flange
5. Cummins B-Series closeup flange
6. Cummins B-Series wide shot
7. Cummins QSX15 turbo flange and manifold (15 liter engine)(notice multiple piece manifold)
8. Cummins QSX15 wide shot (for size reference I held up a nickel) four studs hold the weight of the turbo up
9. Isuzu Heavy Diesel flange in an 80k lb. machine
10. Isuzu Heavy wide shot (note long studs and spacers on exh. manifold to head)
11. Isuzu Medium Diesel in an eight ton vibratory roller

I'll break this up into a separate post for the other stuff I found out.
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Old 07-24-2009, 03:59 PM   #442
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They could alleviate stretch, if they were stacked correctly, and if they are serarated with bite then they also could help out in locking. I was just saying if they go all the way flat with the bolt preload on the washer its not going to help the thermal expansion end of things.


Edit: The preload is roughly 30 percent of maximum. Thats the key, leave some room for it to breath. Joint load bearing at this torque is still only 23000 lbs... Ship turbo anyone?

Last edited by TravisR; 07-24-2009 at 04:12 PM.
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Old 07-24-2009, 04:34 PM   #443
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yeah, the weight of the turbo is NOT what is stretching the studs. the thermal expansion of the flanges is.
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Old 07-24-2009, 04:44 PM   #444
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Why aren't we seeing the same sort of issues with the DP/Turbo flange nuts and studs?
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Old 07-24-2009, 04:52 PM   #445
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I think that this is great info that sixshooter posted. Why try to reengineer when we could stand on the shoulders of giant... turbos.

I think that proper stud and nut usage may involve more than just screwing it in and nutting it up (even though that's a lot of fun ). Proper lube, -stud depth-, stud torque amounts, nut torque may matter a lot. This is not discounting proper studs and nuts.

Regarding stud depth, I found this thread on the internet--

VWvortex Forums: Raceware head Studs

Read the big long post from Raceware. Here's an excerpt:

"
For the record independent tests have shown that "jamming" a head stud into the block can actually cause a residual radial stress component in the shank of a stud that will cause it to "unwind" and loosen later in operation. After RACEWARE proved for more than 15 years that it's better to NOT jam the stud into the block, ARP posted a "Tech Tip" on the back cover of National Dragster News stating that it was NOT necessary to jam the nut into the block to keep it from loosening - something that engine fastener engineers have known for about 100 years or more...

In addition RACEWARE specifically designs it's studs with long bottom threads so that the shank of the stud does not bottom on the head deck surface. We do this because when the shank of a stud bottoms on the deck surface, the first several stud threads that engage the block threads can over-stress the block threads. This means that the shank against the block deck style head stud is more prone to crack and pulling the top few threads of the block and stripping the bolt hole, while the RACEWARE fasteners do not over-stress the block threads."

There is actually a shop nearby with a few porche racecars on route 1 in Laurel. Maybe I can stop by and ask them what thier experiences are.
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Old 07-24-2009, 04:52 PM   #446
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Quote:
Originally Posted by jayc72 View Post
Why aren't we seeing the same sort of issues with the DP/Turbo flange nuts and studs?
Because the DP flange isn't cast iron, and it's also further away from the exhaust ports.

The diesel stuff is great empirical data (especially the variety of mounting orientations, which has been a topic of discussion), but there are two issues
-Weight of the turbo doesn't necessarily matter, it's heat that stretches the studs
-Diesel EGTs are extremely low. A modern stock Diesel will never see anything over about 1100 degrees. Even the hottest Duramaxes don't see more than 1500, and that's only recommended for EXTREMELY short bursts. We see extended periods where EGTs are in the 1600+ range.
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Old 07-24-2009, 04:55 PM   #447
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I have scanned the shop manual pages for the Perkins/Caterpillar, Cummins, and the Isuzu Medium Diesel instructions for replacing the turbo on the manifold. These were all chosen because they use M10 x 1.5 size studs and I believed that to be applicable to our interests.

If anyone wants to play with them, I can get the Cummins M10 x 1.5 studs and nuts pictured in my last post at cost, but I still think you need to try to use a raised stamped metal gasket in between. Cummins gets 3.87 apiece for the studs and 1.22 for each nut. Cummins list price on the studs is 5.05! I'm not interested in getting in the business of selling a bunch of little hardware, but I'd do it for a couple of guys to try out.

I still think you need one of these for $14 T25 Stainless Stamped Steel Gasket
Attached Images
File Type: jpg Perkins.JPG (471.7 KB, 153 views)
File Type: jpg CumminsTurbocharger.JPG (208.6 KB, 153 views)
File Type: jpg Isuzu Turbocharger Mounting.JPG (359.3 KB, 152 views)
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Old 07-24-2009, 05:02 PM   #448
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FM's latest generation of systems uses a cast upper DP section. But isn't the issue the rate of expansion between the studs and the cast iron manifold? On the typical DP connection we've got studs into the cast turbo, so similar issue no?

Maybe the EGTs are just too high in general, and that is the actual problem. The studs/nuts are just a symptom. What kind of EGTs does a stock MSM see on the track?

Do OE turbo setups have this issue when tracked?
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Old 07-24-2009, 05:08 PM   #449
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FWIW, I've seen turbos on some diesel machines glow when worked really hard, but not bright electric orange or anything.
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Old 07-24-2009, 05:08 PM   #450
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You know, the common wisdom has seemed to be not to use a gasket between the mani and the turbine inlet, or at least that one was not needed. But given the spring nature to the gasket design (the ridge, just like the stock head-to-mani gasket) it could be good to have. Is there a known down side to using one? In other words, it is damn cheap, so why not use one?

FWIW EGTs are typically not as hot on turbo diesels as on turbo gas engines. That is one of the reasons the diesels can easily run variable vanes on the turbines (and gas engines cannot); the thermal conditions are not as harsh.
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Old 07-24-2009, 05:19 PM   #451
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Quote:
Originally Posted by ZX-Tex View Post
You know, the common wisdom has seemed to be not to use a gasket between the mani and the turbine inlet, or at least that one was not needed. But given the spring nature to the gasket design (the ridge, just like the stock head-to-mani gasket) it could be good to have. Is there a known down side to using one? In other words, it is damn cheap, so why not use one?

FWIW EGTs are typically not as hot on turbo diesels as on turbo gas engines. That is one of the reasons the diesels can easily run variable vanes on the turbines (and gas engines cannot); the thermal conditions are not as harsh.
because when the metals expand and a leak occurs it cracks the gasket and you have to replace it. If you do a gasket, call "twins turbo" and see if they'll make inconel gt28 gaskets like they do for the T4's. They said the inconel gaskets have never failed...even the "test" gasket they made, even testing with leaks to see if it would break, is still on the car.
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Old 07-24-2009, 06:15 PM   #452
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ok, so I just talked to Eric at Twins Turbo and he said there's a strong possibility that when the metals expand, contract and grow that exhaust gas could directly contact the studs and heat them unevenly. His inconel gasket could help with this (although he said he didn't know enough about the car to speculate) and would consider making a few for us if we wanted to try it.

At this point, I'll try anything.
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Old 07-24-2009, 06:30 PM   #453
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nvm

Last edited by sixshooter; 07-24-2009 at 10:03 PM.
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Old 07-24-2009, 06:38 PM   #454
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does anyone know why BEGi specifically says not to use a gasket in their kits?

thanks for the info BTW 6shooter.
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Old 07-24-2009, 06:39 PM   #455
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Quote:
Originally Posted by sixshooter View Post
OEM SR20DET T25 gaskets in those Silvias don't usually fail do they?
yes...this is the way:

made of inconel.
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Old 07-24-2009, 07:03 PM   #456
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I didnt get a gasket with my BEGI kit so that probably a no.
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Old 07-24-2009, 07:12 PM   #457
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I've been thinking of getting a tube of this for gaskets:
Deacon 8875
This might work too:
Flamemaster CS 1900

I also like the use of stainless studs. Stainless only has 30% the thermal conductivity of regular steel so they're likely to stay cooler. Hopefully spookyfish or someone can bring some to market. The only other option I've found is using stainless allthread rod.
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Old 07-24-2009, 07:19 PM   #458
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Good info today. Couple of notes:
* So, more thread inside the MF. No shank or at least don't torque them down on that. My new studs are shank-less and around 45-50mm long. Of which 25-30mm will go inside the MF.
* Shouldered nuts, I am all for it. Washers bend anyway.
* Not happy that our studs protrude inside the manifold (they see gas). This means more heat
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Old 07-24-2009, 08:30 PM   #459
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Quote:
Originally Posted by Doppelgänger View Post
It would keep them from being able to turn/loosen...yet still stretch as needed. But that brings me to my next question... are we trying to eliminate stretch completely or find a way to deal with it?
There's 'elastic stretch' which is ok, like a rubber band. Then there's "plastic stretch" like syran wrap when you stretch it too much - it just gives up, lets go. You really want to never change the stretch, but even if you do, you want to make sure you're well away from the plastic deformation line.


Quote:
Originally Posted by bryanlow View Post
I've been thinking of getting a tube of this for gaskets:
Deacon 8875
This might work too:
Flamemaster CS 1900

I also like the use of stainless studs. Stainless only has 30% the thermal conductivity of regular steel so they're likely to stay cooler. Hopefully spookyfish or someone can bring some to market. The only other option I've found is using stainless allthread rod.
"It is elastomeric at operating temperatures from -65 deg F to 400 deg F"

I think not.

Low thermal conductivity is not really going to keep it much cooler - maybe in a short transient, but yeah.... Look for something which can deal with the stretch - which means 1) Doesn't change a lot with temps, and 2) Is strong enough you're nowhere near the stretch point.

The higher the temps, the more room the stud needs between the plastic deformation range.
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Old 07-24-2009, 08:53 PM   #460
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Now what you need is a shape memory alloy gasket with the stamped ridge.
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