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Old 05-15-2017, 06:07 PM   #1
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Default Steampipe manifold failure

Hi,

I know that many many Miatas have difficulty keeping manifolds together under intense road racing use, and on 2 dedicated racecars I have had a similar manifold failure at the collector.

In both cases the collectors are extremely heat effected and very very brittle, infact you can see in the following picture how crystalline the structure has become where the manifold has torn. This particular manifold didnt have as much penetration as would be ideal which is my fault, however just like the other one it tore right through the steampipe, it wasnt simply a weld failure, or perhaps I am wrong, educate me.

Can anyone give some feedback, advice, or share their own experience?





Thanks,
Dann
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Old 05-15-2017, 06:23 PM   #2
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Re-weld with Gussets/supports
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Old 05-15-2017, 06:50 PM   #3
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Do you mean from the flange to the manifold runners?

And while this is an obvious thing to try, what I also want to know is if this is the same failure most miatas have, or if this is a flaw in my design, technique etc?

Dann
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Old 05-15-2017, 07:33 PM   #4
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The last 2 I've seen crack, were from ARtech, and cracked in the same exact spot.
He re-welded and gusseted them. See 99mx5's thread for pics of one of the examples.
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Old 05-15-2017, 07:37 PM   #5
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Pretty much what I expected.

Anyone else?

Dann
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Old 05-15-2017, 08:45 PM   #6
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What material? Certain materials are more susceptible to cracking than others especially when hot. I tried 321SS this time around because it should be much more stable at the temps we see. 304 is somewhat garbage compared to 321 at egt temps.
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Old 05-15-2017, 09:03 PM   #7
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we have had issues with "steam pipe" lately too...we figure the quality of the pipe itself (from China?) these days is lower. We have similar crystalizng.
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Old 05-15-2017, 09:23 PM   #8
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The solution is a cast manifold. FM or Trackspeed.
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Old 05-15-2017, 09:32 PM   #9
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Quote:
Originally Posted by nitrodann View Post
Hi,

I know that many many Miatas have difficulty keeping manifolds together under intense road racing use, and on 2 dedicated racecars I have had a similar manifold failure at the collector.

In both cases the collectors are extremely heat effected and very very brittle, infact you can see in the following picture how crystalline the structure has become where the manifold has torn. This particular manifold didnt have as much penetration as would be ideal which is my fault, however just like the other one it tore right through the steampipe, it wasnt simply a weld failure, or perhaps I am wrong, educate me.

Can anyone give some feedback, advice, or share their own experience?





Thanks,
Dann
The metal near the weld becomes hard/brittle when welded and is more susceptible to cracking than the material outside the heat affected zone. Using different filler metals helps with this for the weld and the area it fuzzes with, the right filler can make a big difference. Which would be best depends on what alloy you are welding with.

I'm not a weld engineer but from memory 304 changes crystal structure or something around 1100*F, and that makes it brittle. 321 is a better material in this regard. The highest stress in that part is near the weld or at the weld. In your case the filler is probably a higher alloy and could take the stress, the base metal could not. IMO the best solution to completely solve the problem is use a material that can handle the temperatures reliably. A second option would be a design change to attempt to move stress from one area to another.
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Old 05-15-2017, 09:38 PM   #10
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You might very well be right but our manifolds were scaling as well, away from the welds. As my mechanic said (who has made manifolds for years) he has never seen them do that before....hence we think it may be a quality of material issue....Chinese steel is having issues in other industry/environments too.

Cast might be an option or solution but not as yet for 1600 fyi.
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Old 05-15-2017, 09:41 PM   #11
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Quote:
Originally Posted by mx5-kiwi View Post
You might very well be right but our manifolds were scaling as well, away from the welds. As my mechanic said (who has made manifolds for years) he has never seen them do that before....hence we think it may be a quality of material issue....Chinese steel is having issues in other industry/environments too.

Cast might be an option or solution but not as yet for 1600 fyi.
I'm 100% on board with it being a material failure, which could surely be a quality problem as well.
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Old 05-15-2017, 10:36 PM   #12
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The material is mild steel, sched 40 buttweld fittings.

Dann
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Old 05-15-2017, 10:40 PM   #13
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Why dont I hear about this happening everywhere? Is it a hardcore track car only issue?

Dann
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Old 05-15-2017, 10:43 PM   #14
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yes
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Old 05-15-2017, 10:51 PM   #15
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Also, what rod is everyone using?

Ive got ER70s-8, as far as my research tells me this is the standard rod for this material, I could choose a ER70s-02 or something with a little less deoxidisers, but to be honest I really dont know enough to make the decision either way and have been using what my welding supplies specialist recommends for the application.

Dann
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Old 05-15-2017, 11:18 PM   #16
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Quote:
Originally Posted by mx5-kiwi View Post
You might very well be right but our manifolds were scaling as well, away from the welds. As my mechanic said (who has made manifolds for years) he has never seen them do that before....hence we think it may be a quality of material issue....Chinese steel is having issues in other industry/environments too.

Cast might be an option or solution but not as yet for 1600 fyi.
FM sells cast 1.6 manifolds. I've put over 40 hrs. on it. Basically, if you're road racing, and you're not slow, you will need a cast manifold. I'm genuinely surprised people are still trying welded manifolds on road raced turbo miatas. It's a problem that has been solved.

Last edited by endura; 05-15-2017 at 11:39 PM. Reason: sp
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Old 05-15-2017, 11:49 PM   #17
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Our manifold is 347SS cast for a reason
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Old 05-16-2017, 12:24 AM   #18
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Of course,

However for steampipe.. which filler?

Dann
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Old 05-16-2017, 10:07 AM   #19
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I used ER70S on my mild schedule 40 manifold. The weld seam of the pipe failed but my welds did not after a few track days and lots of street miles.
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Old 05-16-2017, 11:13 AM   #20
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Quote:
Originally Posted by acedeuce802 View Post
I used ER70S on my mild schedule 40 manifold. The weld seam of the pipe failed but my welds did not after a few track days and lots of street miles.
Look above: Dann is asking ER70S-8 vs ER70S-2

Wow on fitting splitting! PICS?
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