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Quad motor is even better than a locking diff if all the motors are modulated right.

I dunno what Rivian does, but I saw that Rimac does 1 motor per wheel, and each motor madly modulates itself during launch control to stop its wheel from slipping... Perfect, maximum torque, all the time.

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There's still some slip though in all these virtual solutions - a wheel has to start slipping for the software to notice and modulation to kick in. With a real locking diff, it's physically impossible for one wheel to spin faster than the other. For sure they can likely modulate the wheel torque quickly though to get the wheels back to the same rotation speed.

In theory, the system can just monitor rotation and "lock" the wheels together with torque as a goal of the system, instead of trying to detect when the tires are slipping.

As a bonus, a computer is smart enough to spin the tires at slightly different rates when turning, instead of dragging them along like a locked diff.

I believe that Rivian offers a quad-motor option, and a standard dual-motor with an open-diff that uses the brakes to try to compensate (similar to a typical AWD system).

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