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Old 04-11-2011, 06:01 PM   #1
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Default Whats better? Cast manifold inconel or welded steel vband

I'm tired of my stud stretch problem, I am currently using a begi cast manifold with stage 8 hardware and a downpipe brace to the transmission, I went from 20 minutes on track failing to about 3 days before failure, but its still failing...

I've searched and see two successful solutions, which is better?

Proven cast manifold with inconel studs?

Expensive v band manifold along with new exhaust housing?

Thanks in advance, looking for first hand experiences with either setup, or better yet someone who's tried both. On track.

Don
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Old 04-11-2011, 06:03 PM   #2
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Same boat... I'm at the point of giving up and just welding the turbine housing to the manifold...
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Old 04-11-2011, 06:03 PM   #3
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I believe inconel either way
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Old 04-11-2011, 06:06 PM   #4
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If you are building a tubular-based setup from scratch, the v-bands are a great option, but the Inconel studs are just as effective.

In-stock, ready to ship.

http://trackspeedengineering.com/sto...-kit-p-98.html
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Old 04-11-2011, 06:13 PM   #5
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Is it gauranteed for any length of time? If it were easier to work on i'd almost be willing to just deal with re tightening. But seriously what's the longest confirmed amount of testing the inconel studs have been subject to?
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Old 04-11-2011, 06:18 PM   #6
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For the record, my inco CHRA bolts are holding up fine after two track days. After 6 or so, I'll call it "fixed".
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Old 04-11-2011, 06:23 PM   #7
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Sav - going to do one track day with the setup as-is and I suspect after it I'll be wanting to upgrade to your Inconel stuff.

My turbo uses 8mm studs though. Can any old machine shop drill and tap the manifold for the larger 10mm stud as well as drill out the holes in the turbo, or is that a specialty job?
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Old 04-11-2011, 06:27 PM   #8
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If you only had 8mm... Unless you've had success in fitting these to a small framed t25 turbo. I don't mind drilling and retapping. I just have a hard enough time fitting a wrench on the 13mm head of the nuts now.
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Old 04-11-2011, 06:35 PM   #9
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Quote:
Originally Posted by Sokool View Post
If you only had 8mm... Unless you've had success in fitting these to a small framed t25 turbo. I don't mind drilling and retapping. I just have a hard enough time fitting a wrench on the 13mm head of the nuts now.
I've got a TD04, but same problem - that's the one thing I'm worried about - I think there's enough room for the bolt holes in the turbo to be drilled out to 10mm but I wonder about the larger nut and getting a wrench on it.

Sav - if you want to sell these as an upgrade to 8mm stud users, if you can send a nut/lock washer from that kit I can see if they will clear the compressor housing. Or, if you have a nut/lock washer at Buttonwillow on the 17th, maybe then.

-Ryan
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Old 04-11-2011, 06:40 PM   #10
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I'm on a TD04 as well.
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Old 04-11-2011, 07:05 PM   #11
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Quote:
Originally Posted by donutbob View Post
Is it gauranteed for any length of time? If it were easier to work on i'd almost be willing to just deal with re tightening. But seriously what's the longest confirmed amount of testing the inconel studs have been subject to?
I think our longest test subject is VagaXT's MSM. I can't give an exact life for them since we've never had one stretch. The nature of this failure is such that it usually happens fairly quickly - a mild/stainless stud gets overheated, loses its tensile/yield strength, and creeps. It's a noncatastrophic tensile failure, not a fatigue failure, so the problem we aim to solve with the Inconel studs doesn't have a significant time factor associated with it. The Inconel won't lose its yield strength at the same temperature, so it won't creep - simple as that. I'm sure the material has some sort of fatigue cycle limit, but it's not something that we could reasonably be expected to test since it could take thousands and thousands of hours to induce.

It's comparable to assembling a turbo downpipe with nylon hardware, and then changing it out for steel - not quite as dramatic, but it's the same idea. You're switching to a material that is designed for the stresses and strains of the environment (inco), vs. one that is known to fail in the same environment (steel).

As far as we know, the 10mm hardware and Stage8 nuts will fit any Garrett T25 .64 A/R or larger exhaust housing (aka standard GT2554R/GT2560R housings). Sonny's car is a GT2560R.

Ryan, I'll throw a kit in the truck this week so you can take a look at BW this weekend.

If someone wants to tell me exactly how much clearance there is from the stud center to the first interference point on the turbo flange, I can tell you whether it'll be possible to fit the 10mm stud. We have to have these produced in pretty large quantity to offer them at that price, so there's virtually no chance of ever seeing an 8mm version of this product. Having said that, if there's significant interest in an 8mm version, we could organize the group buy and have them made. We'd have no way to test them and no ability to offer refunds if they fail, however, which is why it's something we've never seriously explored.

FYI - our upcoming turbo kits will have these studs as standard equipment. In our view, they are an absolutely required addition to any turbocharged Miata that sees track duty.
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Old 04-11-2011, 08:04 PM   #12
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Ok, out of curiosity. If you were to do the work, tap my manifold to accept the new studs, install the turbo with your hardware including new bolts etc, would you gaurantee it for any period of time, or number of events? If so how much? I'm in the northern bay area, I almost exclusively do all my own work but I'd love to "buy" a solution to this problem.
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Old 04-11-2011, 08:15 PM   #13
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Contact us via the website for something like that.
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Old 04-11-2011, 09:15 PM   #14
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Quote:
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I think our longest test subject is VagaXT's MSM. I can't give an exact life for them since we've never had one stretch. The nature of this failure is such that it usually happens fairly quickly - a mild/stainless stud gets overheated, loses its tensile/yield strength, and creeps. It's a noncatastrophic tensile failure, not a fatigue failure, so the problem we aim to solve with the Inconel studs doesn't have a significant time factor associated with it. The Inconel won't lose its yield strength at the same temperature, so it won't creep - simple as that. I'm sure the material has some sort of fatigue cycle limit, but it's not something that we could reasonably be expected to test since it could take thousands and thousands of hours to induce.
If any other nerds out there like myself want some numbers for reference, my old materials textbook lists the tensile strength of Inconel 718 at 120 ksi at 1400F. To put that in perspective, the yield strength of 1020 (plain carbon steel) at 1200F is about 60 ksi.

So yes, inconel really is magic.

EDIT: The coefficients of thermal expansion really aren't that different (7.0 vs. 7.3 microinch/F), it's just the stress imparted by the more rapidly expanding turbine housing.
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Old 04-11-2011, 10:33 PM   #15
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Contact us via the website for something like that.
I appreciate your r&d in solving this matter for my track going Miata. I've sent an email via your site.

Don
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Old 04-12-2011, 11:01 PM   #16
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Savington, i sent an email via the link on your site but haven't heard back, is there a better email address you can provide me? Thanks again.
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Old 04-13-2011, 12:54 AM   #17
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I did see it, I'll be back to you by tomorrow.
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Old 04-13-2011, 01:15 AM   #18
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The problem wrt drilling out for 10 mm studs may not be the turbine, but the manifold. I have an ETD Shorty manifold, and I'm not sure it can be drilled out and accept 10 mm studs.
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Old 04-13-2011, 02:24 AM   #19
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Quote:
Originally Posted by JasonC SBB View Post
The problem wrt drilling out for 10 mm studs may not be the turbine, but the manifold. I have an ETD Shorty manifold, and I'm not sure it can be drilled out and accept 10 mm studs.
For what reason?

Don't know about the ETD but my greddy cast manifold shouldn't have any issues with it that I can think of.
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Old 04-13-2011, 10:43 AM   #20
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Quote:
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For the record, my inco CHRA bolts are holding up fine after two track days. After 6 or so, I'll call it "fixed".
That is good to hear. I was starting to worry that my vband investment was in vain.
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