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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain.


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Old 01-02-2023, 01:03 AM   #15
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Originally Posted by Joon525 View Post
Any pictures of this? (assuming this is a custom setup)
The mid muffler.

The break was midway above this.

Heat could definitely be a factor.
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Old 01-02-2023, 01:52 AM   #16
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Is it also possible that the muffler could have bounced or been bumped into the drive shaft?

Haven't seen harmonics mentioned so I'll throw it out there as a possible contributing factor. If you are racing around off road it's possible you hit some weird frequency between the front and rear bouncing around at different rates and moving around relative to each other. If it's a track, that might be repeated each lap.

More likely heat or muffler related though.
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Old 01-02-2023, 02:10 AM   #17
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Of course having said all that, it was always a risk running carbon on this car!
At least it was spectacular.
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Old 01-02-2023, 02:42 AM   #18
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There's evidence of a polish mark on the muffler (cover?) and the weld looks like it's missing some material?
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Old 01-02-2023, 08:03 AM   #19
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At least it was spectacular.
...it was spectacular when my wife asked the actual cost...
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Old 01-02-2023, 08:07 AM   #20
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Is it also possible that the muffler could have bounced or been bumped into the drive shaft?

Haven't seen harmonics mentioned so I'll throw it out there as a possible contributing factor. If you are racing around off road it's possible you hit some weird frequency between the front and rear bouncing around at different rates and moving around relative to each other. If it's a track, that might be repeated each lap.

More likely heat or muffler related though.
I like your thinking, but there is not enough upward play in the exhaust system to get close enough to the shaft (it would hit a solid mount that I have fitted off the gearbox cross member first).
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Old 01-02-2023, 08:11 AM   #21
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There's evidence of a polish mark on the muffler (cover?) and the weld looks like it's missing some material?
Well spotted.... although that pic was from an earlier escapade, pre break
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Old 01-02-2023, 08:53 AM   #22
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^^^this


How much design factor to account for scratches/divots? Stress risers lower actual critical speed.

Also interesting but might be coincidental, the failure occurred approximately where the stock driveshaft is divided.
I was looking at the same thing. My DDS AL shaft broke exactly in the middle due to exceeding its critical speed.
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Old 01-02-2023, 02:44 PM   #23
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I was looking at the same thing. My DDS AL shaft broke exactly in the middle due to exceeding its critical speed.
Ah, that was yours! Now I remember. You were on a dyno and felt no warning.
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Old 01-02-2023, 07:24 PM   #24
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Since you already have the machined end parts have you considered buying a CF driveshaft blank and bonding up a new one?
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Old 01-02-2023, 07:52 PM   #25
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Quote:
Originally Posted by blsfrs View Post
I was looking at the same thing. My DDS AL shaft broke exactly in the middle due to exceeding its critical speed.
I don't trust anything DSS makes after your failure. That was a huge oversight by a company that has "drive shaft" in their name.
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Old 01-02-2023, 07:55 PM   #26
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Originally Posted by grumpysnapper View Post
Yes that was the initial thought at the time by everybody, but we all became less sure that it may have been the (only) factor when we removed the shaft.

I'm confident that it hasnt had a "big" rock strike in that particular area (and even the more exposed portion closer to the diff is in very good condition).

The area surrounding the failure is quite well protected.

However of course I cant rule out some sort of impact at some point.

I have refitted the alloy driveshaft that it replaced.
Alloy? Chrome moly or Al or ? 2 piece? At this point I'm a big fan of the stock drive shaft.
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Old 01-03-2023, 02:18 AM   #27
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Wasn't stock 2-piece made such, so that to allow it to buckle in case of frontal crash impact, so that engine can be pushed under passenger compartment?
It's drawbacks .. i guess slight (but probably not that immense) play in extra joints, slightly more expensive .. and a bit heavier .. hmm .. i wonder if it's not worth to leave it as is, if it's designed/engineered for extra safety ..
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Old 01-03-2023, 02:34 AM   #28
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Wasn't stock 2-piece made such, so that to allow it to buckle in case of frontal crash impact, so that engine can be pushed under passenger compartment?
Yes. Also with all other properties being the same, shorter driveshaft will be able to spin faster without failing. I'm not a fan of any of these single-piece driveshafts. The only upside is a few kilos trimmed. Not worth it.
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