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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain. |
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05-05-2017, 08:30 AM | #43 |
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05-05-2017, 10:25 AM | #44 |
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Jethot does an awesome job; just had bad luck. Maybe its the quality of the pipe used by Shiv / Open Flash (their manufacturer).
Looks great, really sucks that happened. |
05-05-2017, 10:54 AM | #45 |
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It was coated with their 2500 degree ceramic coating. But what gets to me is that yes there is a wide crack, BUT the only hole is on the weld in the seam. I stuck a toothpick in there. Me and my wife hit it with a flashlight and the light went straight thru the hole at the seam of the weld. I'm no welding master, nor engineer, but the stress cracks that go to the right and left of the center hole were all caused by the hole being made where the weld was. Maybe someone can confirm this aswell i inculded a close up. Btw this header was ordered before there existed ofh2, and ofh3 .. I'm guessing I had one of the beginning headers give or take, mayhne someone else can confirm that I do have the original number.
This all happened while our temps are low. In my area. Btw I'm on long island ny... So yes we had few hot days. Yet I drive at 6 am which we have had the temps in the 50s and 40s.and I go home in the evening after sun down, again temps drop 50s 60s. I avoid most traffic jams as well I'm usually rolling never really bumped to bumper.so I do get air circulating. |
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05-05-2017, 03:17 PM | #46 |
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Crack in My ofh
That pin hole is caused by a fish eye more than likely, a structural defect in the weld. The handful (3 or 4 so far, it's not a high rate) of OFH that failed in this forum have had the crack propagating in this way.
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05-05-2017, 09:34 PM | #47 | |
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Thank you... this confirms my suspicion.. this is now here for future reference. Sadly I got assed out. BUT I ordered new JDL UEL headers and redoing full exhaust so better for me, even tho the pockets hurt, not an expected expense. Confirms what the truth culprit is... this can stay for future reference. Last edited by FISHBURGLAR; 05-06-2017 at 07:07 PM. |
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The Following User Says Thank You to FISHBURGLAR For This Useful Post: | gtengr (05-06-2017) |
05-06-2017, 09:30 AM | #48 | |
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Shiv, If you may read the rest of this thread. Once I receive the new header I will pull our my OFH clean off all carbon deposit and show inside and outside coating and send a video plus more pictures. All signs to me point to a header from the bad batch. As I mostly baby the car I can see how it lasted longer to crack. Winters I don't 'll drive her. |
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05-07-2017, 05:56 AM | #49 |
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About the topic of coating the inside of an exhaust, I'll post here the suggestions of Zircotec, which is one of the best professionals on ceramic coating:
Q28. Can you coat the inside of my exhaust? – Here at Zircotec we only apply our ceramic coating to the external surfaces. We are aware of some paint products that are applied internally. The conditions inside an exhaust manifold are quite extreme with gas at temperatures in excess of 1,000oC; pulsing gas flow of more than 20 m/sec; large pressure and temperature variations; significant vibration; and thermal stress. We are concerned that it is impossible to prepare the internal surfaces of a pipe or manifold sufficiently to receive a paint, and with such arduous operating conditions we fear that these products can easily become detached, causing serious damage to downstream components such as turbochargers and catalysts. Furthermore, these products narrow the flow channels and can restrict flow (even a thin paint can reduce the available flow area by up to 2%) giving rise to reduced engine performance. Our recommendation is that you limit any coating to just the external surfaces. You might consider polishing the internals to avoid any rough edges or corners, but our technical experts really do not advise putting any form of coating on the inside of an exhaust manifold or exhaust system. Source here: http://www.zircotec.com/support/for-motorsport/faq/ |
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05-07-2017, 09:32 AM | #50 |
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What I'd be concerned about and the reason I would not get an OFH, is that there's no flex pipe of any sort. It's just common sense that if you have a rigid pipe connected to an engine that flexes (LOL, not that there's all that much torque on it!) and it extends out to the rear of the car, that something has to give.
IMHO this has nothing to do with heat stress, steel pipe can handle heat. But steel pipe is not so good with torsional and bending stresses over and over. |
05-07-2017, 10:01 AM | #51 |
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I agree that a correct design should have a kind of flex like the following:
or It also matters the quality of the material and the manufacturing technique. I just posted the answer of Zircotec, to emphasize that the suggestion of coating the inside of a manifolld is not relevant and in fact can cause more problems. |
05-07-2017, 10:03 AM | #52 | ||
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Crack in My ofh
Quote:
Quote:
The steel is MORE than strong enough for those stresses. Steel is also very fatigue resistant for a cheap metal, even stainless (fun fact, stainless is weather than most carbon steels). The exhaust is also not rigidly mounted to the body. There's one small metallic bracket in the middle (1 bolt, so essentially a pinned connection), and flexible hangers in the back, so the exhaust can move around (and has to since the exhaust grows about 3/8ths of an inch in length when it warms up). The stock exhaust doesn't have a flex section past the header either. Exhaust parts on street cars rarely fail from anything besides defective welds. Sent from my iPhone using Tapatalk |
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05-07-2017, 10:04 AM | #53 |
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Flex or slipjoint inserts were there on several 1st gen aftermarket headers for twins. Most of later ones hadn't such. I guess failure rate by statistics due not having them was low enough to not bother, instead simplify & cheapen manufacturing & smoothing flow, hence imho not worth to be overly concerned about them not being there.
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05-07-2017, 02:34 PM | #54 |
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Chuck it away. Re-fit the original manifold and move on.
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05-07-2017, 02:35 PM | #55 |
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The entire exhaust is not rigidly mounted to the body, but the headers are rigidly mounted to the heads. When the car is warmed up the head flanges want to expand farther apart. Since the flanges are bolted to the head, they are restrained, and the stresses increase in the pipes. This doesn't imply that all headers without an expansion joint will fail, but that doesn't mean all headers can run without an expansion joint indefinitely without thermal cycling issues.
Heat cycling and/or vibration cause nearly all exhaust structural issues, and fatigue is the failure mode. The weld is just the location it happens. The welds are usually the failure point because the discontinuity of the joint and the HAZ are typical trouble spots for fatigue. |
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05-07-2017, 03:02 PM | #56 | |
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Absolutely, the CTE mismatch between the aluminum motor and steel header causes the driving forces behind the header failure, but a well made header should be strong enough to withstand those for a life time 999 times it out of a 1000. I guess there will always be someone that gets unlucky and gets a bad piece. Sent from my iPhone using Tapatalk |
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The Following User Says Thank You to Yoshoobaroo For This Useful Post: | FISHBURGLAR (05-07-2017) |
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