Correct torque for an 8mm turbine stud? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-09-2008, 11:27 AM   #1
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Default Correct torque for an 8mm turbine stud?

While fiddling with the downpipe and wastegate I managed to shear two studs (stover nuts did not want to come off). Begi was kind enough to send me some replacements. Using the double nut method what should I torque the 8mm studs to on the turbine exit. Then, what should the nut be torqued to once the downpipe is back in place?
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Old 09-09-2008, 08:21 PM   #2
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no one knows? There seems to be some confusion (or at least I'm confused) as to whether you tighten the studs into the turbine with half the torque you will be applying to the nut once the downpipe is in place or if you should rather torque to the studs into the turbine housing twice what you will apply to the nuts. Any specific figures I should be shooting for? I'd rather not shear any more studs out of sheer (haha) ignorance.
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Old 09-09-2008, 08:27 PM   #3
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I say lube the studs with that super slick moly **** (look it up), and torque to like 25 ft*lbs. Make sure you chamfer the manifold where the studs go in so that the two tapers meet each other. Then do the nuts to like 15 ft*lbs. Those numbers are just out of my ***, but should work. FWIW, there are charts that show bolt diameter/torque values.
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Old 09-09-2008, 08:36 PM   #4
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I'd imagine the turbine housing is chamfered already as the studs came preinstalled from Begi. I'm just replacing some I broke. I also figured there were charts, but #1 I don't know where to find them and #2 I wasn't sure if heat and vibration would effect the value of the numbers. Thanks for the tips, I would not have guessed the torque values would be so low. I probably would have sheared one again.
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Old 09-09-2008, 08:41 PM   #5
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From a Haynes manual

M6 6-9 ft*lbs
M8 14-21 ft*lbs
M10 28-40 ft*lbs
M12 50-71 ft*lbs

And I got a dollar that says you have a hanes manual, and therefore you have the chart I'm reading from.
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Old 09-10-2008, 01:20 AM   #6
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you owe me a dollar
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Old 09-10-2008, 09:21 AM   #7
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Why pretorque the studs at all? I just screw them into the turbine housing finger tight. I know that's what ARP instructs when you use their studs on other engine parts.
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Old 09-10-2008, 11:02 AM   #8
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Tim, if you did that, you would be defeating the purpose of using a stud. It would work like a bolt then.
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Old 09-10-2008, 01:10 PM   #9
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uhhhhhhhhh no comment.
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Old 09-10-2008, 01:50 PM   #10
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If you are using the deformed nuts you'll either end up backing the stud out when you go to remove the stud, or you'll break the stud. Like Tim suggests, less is more.

I'd rather deal with a lost nut or having something come loose than a stud broke off in the turbo. This is why I use nordlocks on the turbo and downpipe.
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Old 09-10-2008, 02:06 PM   #11
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I have had nothing but problems out of using the nuts that BEGi sent me, almost everytime I've had to remove them, the whole stud comes with them.
I'm switching to the Nord Locks.
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Old 09-10-2008, 02:09 PM   #12
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I swtched to the copper nuts y8s recommended for that reason. Nuts would not come off, but the whole stud would come loose.
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Old 09-10-2008, 02:14 PM   #13
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"Nord Locks" ehh...thanks for the name. I know FM sells them.

FM: http://www.flyinmiata.com/index.php?...umber=36-30300
$1.95 per pair stainless

McMaster: #91074A130 Mild steel, $0.52 per pair (but you have to buy 25 pair hehe)
#91812A230 316 stainless, $1.53 per pair, comes in a bag of 5 pair, perfect for a downpipe.

I'm so cool that McMaster moved their NJ location right onto my way home from work. They love me that much. Will call FTMFW especially when you buy lots of heavy weldells for manifolds and such
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