03-31-2021, 10:04 AM | #1 |
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Rear Axle Transmission. M3 and M4 - explained, Episode 16
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03-31-2021, 10:15 AM | #2 |
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I followed this until about 5:00 when he talked about his favorite detail - the left output shaft being slightly larger. I thought nothing that followed even began to address what?, why? or how?
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03-31-2021, 10:40 AM | #3 | |
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I believe it's angular momentum in physics
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03-31-2021, 11:09 AM | #4 | |
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03-31-2021, 11:11 AM | #5 | ||
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03-31-2021, 01:00 PM | #6 |
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Actually he does explain it fairly well, albeit in very technical terms. What I understand is that the two output shafts are designed with a different stiffness to minimize harmonic behaviour in lower traction conditions; read reduce axle hop.
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03-31-2021, 03:38 PM | #7 |
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Yes, should be spot on. The torsional rigidity is higher for the left axle, leading to different harmonic behaviour both in amplitude and frequency, avoiding under equal load (diff lock) both axles amplify each others distortive dynamics resulting in hop. Is indeed a clever trick!
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04-01-2021, 02:41 AM | #8 |
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This is one very VERY advanced differential.
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04-01-2021, 04:56 AM | #9 |
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Yea, it's a pretty good electronic LSD unit but don't let this video make you believe that it's something new; it's literally the same identical technology used in the F8Xs M cars, of the last generation.
F80 M3 / F82 M4 Active M Differential: Deep Dive and Interview https://f80.bimmerpost.com/forums/sh....php?t=1018024 . |
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04-01-2021, 05:22 AM | #10 |
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From some of the comments made by journalists in that the G80 seems to be able to accelerate even with high yaw angles (better than F8x), I was expecting to see some torque vectoring technology. Twin clutch packs. But nope, just the same carry over diff from F80.
The programming that controls diff function is extremely important, perhaps they have taken this to another level? Or maybe it is a just the wide 4S that helps. |
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04-01-2021, 06:07 AM | #11 | |
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04-27-2021, 06:15 AM | #13 | |
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Cadillac discovered that if they employ the proper ratio of torsional stiffness between the two IRS half-shafts (based on that huge number of variables overall dynamics problem), they can allow for absorption/release (so to speak) of said energy and greatly reduce the cyclic build-up/release cycle. Said design was first on the gen2 CTS-V but then also shared with other GM cars with an IRS.
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04-27-2021, 06:18 AM | #14 | |
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Maybe axle hop was more of an issue on the G8X so they had to remedy it.
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