EPIC nuts/studs loosening thread (reposting stupid stuff without reading = warning) - Page 22 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-23-2009, 07:40 PM   #421
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IDK the material, but we are a Cummins dealer and all of those parts are on the shelf in the parts department. I can tell you that they use spacers on the exhaust manifold to head bolts and studs (some configurations use bolts and some use studs). It wasn't until recently in this thread that I realized why. The cast iron exhaust manifolds are either two or three piece manifolds to help with the thermal expansion problems and prevent cracking. A nineteen liter six cylinder has a pretty long exhaust manifold. And a hefty turbo.

I have to duck by the office tomorrow. I'll try to take a closer look at how that's done. I'll see if I can take some pics, too. We also have some other brands of big turbo diesels that might be worth paying attention to as well. I'll pay attention to turbo weight support bracketry as well.
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Old 07-23-2009, 08:48 PM   #422
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Quote:
Originally Posted by AbeFM View Post
3) Put them on a little loose, and tighten them a few times the first day, then once a day, then once every couple days. This breaks them in under a month.
I had a theory that they "break in".
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Old 07-23-2009, 08:56 PM   #423
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Quote:
Originally Posted by TravisR View Post
Spring washers effectively become... ineffective once the torque on the stud is reached. I think its a combination of problems.

One is that the studs are loaded to their torque maximums. This means the stud is stretched as far as it will reasonably go without plastic deformation. When they heat up two things happen. The maximum torque load allowable goes way down because tensile load is a function of temperature, and simultaneously the stud is stretched by the expanding steel under thermal stress. When the stud stretches it goes past the allowable load, and quickly into the region where the stud is permanently lengthened known as a plastic deformation. This happens over a 50-60 cycles, and suddenly... your **** is loose.
Maybe this is why the 034 folks told Bryanlow to use Resbond and don't torque very much!
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Old 07-23-2009, 08:56 PM   #424
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holy smokes....22 pages?!?!? what rock have i been living under?
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Old 07-23-2009, 09:01 PM   #425
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Instead of a thick spacer of beleville washer, is there some kind of springy gasket material (to go between manifold and turbo), that can take up the growth in the flange thickness without increasing the stretching load on the studs.

What happened to the idea of a stud material that has a much lower spring constant k (stretches more)? This would be able to take more strecthing without increasing load.
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Old 07-24-2009, 06:22 AM   #426
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It's about time I chimed in for input. Andrew, I'm sure you can vouch for me about my lap times and such.

Here's a potential solution RoadsterTuner (Erik) and I are still working on. This setup is still undergoing long-term testing (since March 21, 2009 at Laguna Seca for the 20th anniversary event).

Custom Heim joint arm to support the turbo from stretching studs and to relieve stress on the turbo studs (10mm, allen-headed custom cut to fit) at high engine temps. Also shown, Stage 8 locking nut hardware (10mmx1.25 version).











After Laguna Seca, flawless operation from the road trip up and down CA and even after another trackday at Thunderhill about 3 weeks later in April. Only after that, the studs stretched minimally and still held well enough to not leak exhaust gases. I would have left the setup as-is for more testing, but the turbo had to come out for a rebuild.

The setup with fresh studs (this time 10mm OEM exhaust header studs) and nut hardware went back in late May for a trackday at Buttonwillow. Not a good day as I overheated a lot due to a botched coolant change that put air bubbles in the system, and oil-logged MAP sensor and a bad, untested Hydra map. Still the studs and nuts were ok, no leaks and the hardware is still on the car right now. Just a little extra turn from the stud stretching a little bit, but all is still well since late May 2008.

The real test will begin at Streets of Willow on Fri. the 31st, followed by Horsethief Mile on Sun. the 2nd. Hot weather and engine torture testing elevation changes. Bring it on. If it holds up, that'll be 3 trackdays plus DDing the car for about 2 months that this hardware setup will go through without a hardware overhaul.

BTW, the heim joint and brackets (other than the one on the turbo) are still from the original setup from March.
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Old 07-24-2009, 06:46 AM   #427
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Nice, always thought a turbo brace would help. What stud material is that? Steel or stainless? What OEM studs are they? Mazda are M10x1.25...
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Old 07-24-2009, 11:56 AM   #428
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Might the engine vibration be creating more force on the studs than gravity?
What about thermal expansion of the manifold and turbo, wouldn't that cause it to pull against the brace?
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Old 07-24-2009, 12:14 PM   #429
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I'm wondering how well a castle nut and cotter pin would work in preventing the nut rfom coming loost. Obviously it won't do **** if the stud comes loose. I know since I went to 10mm hardware (whatever FM provides) I did 2 track days, 9 autoXs, daily driving, hours of beating the car in the mountains, dozens of high speed runs and have not had a problem (knocks on wood). I know it's not quite the stress of a dedicated track car/enduro race, but it's obviously more abuse than just putting around to and from work.

The other idea I had, is to tie 2 of the nuts together.... think the nifty tool that slides between the cam gears when chaning the t-belt. I think if a brace was designed to hold the left and right nuts to the top and bottom of eachother, it would work. In that case, the nuts would have to be at specific turns to line up, but adding a bit more or less tq to get things lined up might not be an issue if everthing is tied together (how much tq would really be lost/gained with 1/6th of a turn of the nut to get the correct alignment?). As for how it would mount securely, I have several theories on how it could be accomplished...

Here is one of my ideas...utilizing my madtyte paintz skillz...and i'm sure if someone wanted to CAD this and have it made, it probably wouldn't be all that hard. The studs would have to be drilled/tapped in the center (shouldn't be hard) and the "tabs" that come off the bracket would have hold in them to allow for small set screws to hold them to the stud. Hopefull this makes sense to some of you....
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Old 07-24-2009, 12:22 PM   #430
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/\ Basically the same end result as the bend up locking tabs will yield and are available off the shelf.
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Old 07-24-2009, 12:25 PM   #431
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OK, i'll be honest here... which bend up locking tabs? I have soo many types of hardware listed in this thread I can't recall this specific one/what it looks like/how it works that you are talking about. Like the Stage 8 things similar to what's on Vega's car?
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Old 07-24-2009, 12:30 PM   #432
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The OEM Nissan S13 ones. The studs are problem #1. Loosening nuts is just a side effect at best.
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Old 07-24-2009, 12:33 PM   #433
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Quote:
Originally Posted by Doppelgänger View Post
OK, i'll be honest here... which bend up locking tabs?
.
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Old 07-24-2009, 12:34 PM   #434
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The ones available on SR20s. Genuine OEM Nissan T25 T28 Turbo Turbine Locking Tab

Keeping the nuts on isn't a big deal, guys. Stage 8 fasteners, drill and safety wire, there are several good options that work. What we need to deal with is the stud material problem.
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Old 07-24-2009, 12:38 PM   #435
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Oh... how the **** did I miss that? Interesting. Now what pages was that discussed on? lol..I can't remember all 24 pages of this thread :sad:
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Old 07-24-2009, 12:41 PM   #436
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Originally Posted by Savington View Post
Keeping the nuts on isn't a big deal, guys. Stage 8 fasteners, drill and safety wire, there are several good options that work. What we need to deal with is the stud material problem.
Figured as much on that. What about tieing the studs together with a similar thing to what I pictured...just going from center to center of the studs? 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?

Yeah, might be a dumb idea.. but maybe it will spark someone else to have an idea...

-Spooky, in response to your post below this... I wish I knew more about different materials and how they react, but I can't. All I can maybe to is put some ideas out there for discussion, sorry.

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Old 07-24-2009, 12:45 PM   #437
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Can someone put a meaningfull first post together??
I started on stainless around here:
https://www.miataturbo.net/forum/t35874-9/#post424085
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Old 07-24-2009, 01:42 PM   #438
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I'm running bolts, not studs. Is there a reason you guys only run studs? Clearance? I suppose they'll stretch just like studs, but I'm curious as to why.
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Old 07-24-2009, 03:10 PM   #439
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Quote:
Originally Posted by JasonC SBB View Post
Might the engine vibration be creating more force on the studs than gravity?
What about thermal expansion of the manifold and turbo, wouldn't that cause it to pull against the brace?
That’s the point, really. I don’t have hard numbers to prove it, but with the success of the brace (with the 10mm studs) is clamping the turbo together with the manifold with minimal stud stretching. I believe that the brace is expanding and a lower rate than the turbo and manifold; therefore, the stress on the studs (shear and tensile) is reduced since the brace (a tensile force) is providing a counter-torque/counter-moment to the torque caused by the weight of the turbo hanging off the manifold.
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Old 07-24-2009, 03:22 PM   #440
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Quote:
Originally Posted by TravisR View Post
belleville's will be ineffective
Travis, do you mean they will be ineffective for locking, or for helping to alleviate (or compensate for) bolt stretch? I agree they probably would not help with the former, but it seems like they could with the latter.

BTW here are some equations for the fellow MEs
http://www.engineersedge.com/belleville_spring.htm

Now that I think about it... I had a 1978 Civic (with a built Accord motor I put together) a long time ago, way before modding Hondas was cool. No turbo. But, at any rate, the stock washers (used under the stock nuts) to hold on the exhaust manifold were REALLY thick Belleville washers, like 0.1"-0.2" thick IIRC.
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