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Old Yesterday, 02:20 PM   #11
Nick M3
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Driving down the highway with mismatched tires on an LSD heating up the clutches (drag on once side, torque on the other) is not at all the same as microscopically more forward torque on one side than the other. If that were the case, then one tire fire would also be extremely unstable.
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Old Yesterday, 04:44 PM   #12
John V
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Originally Posted by Nick M3 View Post
Differentials never provide equal torque, so why would micro-management of torque be necessary?
I'm confused by what you mean here. Open differentials do provide equal torque across their two outputs.
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Old Yesterday, 05:08 PM   #13
rumatt
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Quote:
Originally Posted by Nick M3 View Post
Driving down the highway with mismatched tires on an LSD heating up the clutches (drag on once side, torque on the other) is not at all the same as microscopically more forward torque on one side than the other.
Of ourse not, given that you added the word "microscopically". But it's just a matter of degree.

I've already conceded that the variance in motors won't matter if it's small enough. But is it? What percent variance is there in motor output for a fixed input power? Initially? And after 5 years of use? I have no idea.

And how much difference can there be before you notice it when driving? I also have no idea.

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Old Yesterday, 07:11 PM   #14
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Until Tesla actually releases the Plaid, I don't think we'll know much about how they implemented it.

But their approach to Dual motors might give some hints. Separate axels, but that's nothing technically different than one motor driving 2 wheels on an axel vs 1 wheel on an axel.

When the Dual Motor S was released, Tesla was able to get longer range on it than the single motor option. The assumption was gearing differences -- so the front axel had a different final drive ratio than the rear axel. But they also mentioned that they could modulate power to the axels -- so at times its FWD and other times RWD.

The modulation of power had me confused, since normally a motor acts as a generator when the rotor is turned -- that's how regen braking works (instead of putting energy into the motor to turn the wheels, the already-moving wheels turn the motor, with energy flowing out of the motor and back to the pack). But then I remembered that there is a neutral setting -- so the modulation of power is basically moving a single axel into neutral so that that axel coasts instead of regen. So the car can do what is most efficient based on the situation.

For the tri-motor, I'm guessing that they are using that same basic setting to enable LSD-like properties on the rear axel to improve handling and get some torque vectoring when needed. Instead of focusing on efficiency, it focuses on power delivery. The single-motor front axel is then used for efficiency.
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