Artech Downpipe crack. Will a repair hold up? - Page 3 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 04-06-2015, 12:38 PM   #41
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No problem, I know that sucks having to keep pulling it! When I was turbo I always ran mild steel 16 gauge as it was cheap and reliable and no brace required because wall thickness was like .065". But alas my exhaust system probably weighed at least twice what yours does and certainly was not as pretty!
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Old 04-06-2015, 12:58 PM   #42
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Quote:
Originally Posted by patsmx5 View Post
No problem, I know that sucks having to keep pulling it! When I was turbo I always ran mild steel 16 gauge as it was cheap and reliable and no brace required because wall thickness was like .065". But alas my exhaust system probably weighed at least twice what yours does and certainly was not as pretty!
I really dont care much about it looking nice.. I really just want to be able to drive the thing without worrying about anything going wrong. I wouldnt be opposed to having an exact duplicate made in a thicker walled piping BUT I highly doubt Artech would eat the cost of that. I'm sure the materials are more expensive and the labor time would be long.
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Old 04-06-2015, 01:59 PM   #43
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Quote:
Originally Posted by patsmx5 View Post

My recommendation is to add a brace to take the load off the downpipe. If that was 16 gauge mild steel tube it wouldn't be cracking since it could handle that load no problem. But it would be heavy and not as pretty. If you want thin wall stainless, you can't put huge loads on it and expect it to last.
How did we conclude this is thin walled? Might it not be 16 GA SST?
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Old 04-06-2015, 02:04 PM   #44
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How did we conclude this is thin walled? Might it not be 16 GA SST?
I measured it with a micrometer.

No, I don't know what gauge it is actually, maybe the guy who made it can chime in? Or the OP can measure it and post. Actually a good point, if it IS 16 gauge then damn, I don't know how you keep breaking it!
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Old 04-06-2015, 03:48 PM   #45
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Abe just got back to me so now I just have to pull the pipe back out and get it shipped over to him
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Old 04-06-2015, 06:47 PM   #46
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DP Is out once again... Off to Abe tomorrow!

Installed/ Uninstalled pics for Artech. No contact with anything anywhere :-/

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Artech Downpipe crack. Will a repair hold up?-20150406_151848_zpskqpert5h.jpg   Artech Downpipe crack. Will a repair hold up?-20150406_170943_zps48ygljre.jpg   Artech Downpipe crack. Will a repair hold up?-20150406_171039_zpsofot1ywm.jpg   Artech Downpipe crack. Will a repair hold up?-20150406_171105_zps0i7yz4hm.jpg   Artech Downpipe crack. Will a repair hold up?-20150406_171110_zpsbdmatmeq.jpg  

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Old 04-06-2015, 07:27 PM   #47
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You need a god damned flex pipe and brace.

Dann
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Old 04-06-2015, 08:17 PM   #48
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Originally Posted by nitrodann View Post
You need a god damned flex pipe and brace.

Dann
Well I guess I need a second flex pipe lol... And I definitely will be adding a brace as soon as I get it back
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Old 04-06-2015, 11:05 PM   #49
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I said you need those 2 things because I know you don't have those 2 things.
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Old 04-07-2015, 09:49 AM   #50
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Shouldn't we be concerned that it's failing through the weld?
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Old 04-07-2015, 10:04 AM   #51
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thats standard failure mode.

Look at the welds in the photo on the downpipe, they are close to textbook perfect. Abe is clearly very skilled.
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Old 04-07-2015, 10:05 AM   #52
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He has a flex pipe in the downpipe and the wastegate pipe.
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Old 04-07-2015, 10:09 AM   #53
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Quote:
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He has a flex pipe in the downpipe and the wastegate pipe.
That I do sir
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Old 04-08-2015, 12:03 PM   #54
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Quote:
Originally Posted by nitrodann View Post
thats standard failure mode.
.
Really, that's weird. Every welding specification I've ever read requires that the material fail in the base metal and not in the weld.

When I worked at Honda we did lots of testing for this exact thing, the tensile specimen was always required to fail in the base metal. If the specimen failed in the weld or in the HAZ then the test was considered a failure.

I don't doubt Abe's skills at all. But in my experience, a failure straight through the weld bead is a big no-no.
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Old 04-08-2015, 12:14 PM   #55
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the way it split makes me think there's stress there, like the bend needed to open up a bit.
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Old 04-08-2015, 12:16 PM   #56
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Quote:
Originally Posted by Efini~FC3S View Post
Really, that's weird. Every welding specification I've ever read requires that the material fail in the base metal and not in the weld.

When I worked at Honda we did lots of testing for this exact thing, the tensile specimen was always required to fail in the base metal. If the specimen failed in the weld or in the HAZ then the test was considered a failure.

I don't doubt Abe's skills at all. But in my experience, a failure straight through the weld bead is a big no-no.
Agreed. I'm no TIG guy but looks like it was just melted together/no filler, and undercut in the process, causing a weak weld.
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Old 04-08-2015, 12:45 PM   #57
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Then why did it also fail the second weld with a nice fat filler mound there.

This is scary. I've welded a bunch of downpipes with no filler, no reinforcements, no flexes (basically any 'street car' setup i've done), and I'm a far inferior welder to abe, while using inferior material (vibrant bends instead of beautiful steam pipe bends).

SO something's off with the car, not the pipe. What that is, I dunno.

How buzzy is your car? Running a chinese flywheel/clutch?
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Old 04-08-2015, 12:53 PM   #58
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Then why did it also fail the second weld with a nice fat filler mound there.

This is scary. I've welded a bunch of downpipes with no filler, no reinforcements, no flexes (basically any 'street car' setup i've done), and I'm a far inferior welder to abe, while using inferior material (vibrant bends instead of beautiful steam pipe bends).

SO something's off with the car, not the pipe. What that is, I dunno.

How buzzy is your car? Running a chinese flywheel/clutch?
Its not buzzy at all... Smooth actually. Its a FM Stg1 clutch with OEM flywheel. I really dont know what in my car would cause it to keep happening. The downpipe will arrive to Abe on Friday and he will have it headed back in my direction early next week. He is going to be adding a slip joint over the cracked weld to reinforce that joint.

The only thing I noticed when removing the downpipe yesterday was that the exhaust seemed to be pulling down on the back side of the downpipe. I'm assuming that was putting stress on the weld that cracked and thats why it split. I fully plan to add a brace and see what happens this time.

In other news, i'm now a pro at pulling my downpipe. Literally had it out in like 20 mins yesterday compared to 2 hours the first time (Granted, the anti-seize was still fresh on the downpipe hardware)
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Old 04-08-2015, 01:06 PM   #59
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That **** gets everywhere but it's worth its weight in gold.
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Old 04-08-2015, 01:07 PM   #60
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Quote:
Originally Posted by TurboTim View Post
Then why did it also fail the second weld with a nice fat filler mound there.

This is scary. I've welded a bunch of downpipes with no filler, no reinforcements, no flexes (basically any 'street car' setup i've done), and I'm a far inferior welder to abe, while using inferior material (vibrant bends instead of beautiful steam pipe bends).

SO something's off with the car, not the pipe. What that is, I dunno.

How buzzy is your car? Running a chinese flywheel/clutch?
I don't know. In one of his pics (this one: http://i119.photobucket.com/albums/o...pszeiucefg.jpg ), it looks like the 2nd weld was not all the way around, there is a spot (that failed) that is still undercut in the pics. Perhaps (again, I don't TIG much so don't know much about TIG) this spot failed and then the crack propegated.

But I dunno. Seems to me something is putting really high stress in that spot. Hence why I recommended a brace.

Random though, but if his EGT's were really high for some reason, would that contribute to this failure?
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