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When Tesla introduced the dual motor model s it had better range and performance (so better in everyway except price).

Would a quadruple motor car (one per wheel) have even better range and performance? Or Was the increase in range and performance not due to the number of motors but due to the ability to remove the rear drive shaft etc?

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It's 4 * 4 ... And also the reduced friction of the drivetrain - the more direct the drive the better and also may have had a weight effect, but given the weight of the batteries that may not really be noticed.

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  • $\begingroup$ Yes, the car would have all the advantages and all the disadvantages of a 4x4 vs normal car. More mass, more complexity (= failure chance), worse efficiency in good road conditions, lower range in these conditions. Meanwhile, it would be much superior for off-road and bad conditions. $\endgroup$ – SF. Jun 19 '17 at 16:21
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The total battery energy capacity is what defines range. The dual-motor system is provided for improved traction and general control, not range. There is no "drive shaft" in any electric car. The single-motor Teslas have the motor over the rear wheels, not at the opposite end of the vehicle the way (obsolete dinosaur absurd design with transmission gear) ICE cars do.

The advantage of a 4-motor config is that you get rid of differential gears on each axle. The disadvantages include the need for a more advanced 4-way torque balancing controller (essentially software differential), increasing the probability of motor failure by a factor of sqrt(2), and probably more total weight (two small motors weigh more than one bigger motor).

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  • $\begingroup$ No driveshaft in any electric car - perhaps you should check out a peugeot 106 electric... $\endgroup$ – Solar Mike Jun 19 '17 at 15:25
  • $\begingroup$ @SolarMike "Peugeot" ha ha ha :-) $\endgroup$ – Carl Witthoft Jun 19 '17 at 16:55
  • $\begingroup$ Was a good car for local running about 90 kmh top, 80km range was a town type runabout. 4 seats small easy to park. $\endgroup$ – Solar Mike Jun 19 '17 at 17:03
  • $\begingroup$ The dual motor Tesla has a longer range $\endgroup$ – SRawes Jun 19 '17 at 22:51
  • $\begingroup$ @SRawes marginally so; and as the non-D models are being phased out, it won't matter much longer. $\endgroup$ – Carl Witthoft Jun 20 '17 at 11:27
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Tesla initially built the Model S with one motor driving the rear wheels. The D model has a second motor driving the front wheels.

Was the increase in range and performance ... due to the ability to remove the rear drive shaft etc?

No. There was no rear drive shaft in the RWD model, the motor was installed behind the rear wheels, against the differential.

The range of the D model is about ~10 miles more than the RWD model with the same battery. I haven't found a statement that says why range has increased. One possibility is there's more scope for regeneration with the AWD model: on the RWD car, regeneration is limited by traction, most of the brake force is supplied by the front wheels.

The increased performance is thanks to the second motor.

Going from 2 to 4 motors allows you to eliminate the differentials, at a cost of having to drive each motor at a different speed, making the electronics more complex: not just the control circuitry, but you need to have two power amplifiers instead of just one.

Whether it'll improve performance depends on which motors you choose: if you replace one 100 kW motor with two 100 kW motors you get more performance but a shorter range, for instance.

An important factor is the power/weight ratio of the motors. I suspect the 2x 50 kW motors would weigh a bit more than a single 100 kW motor, as you have to duplicate some items that don't directly contribute to output power, like the commutator and the motor shaft. The 2 casings will weigh more, too. Whether the extra weight will be offset by eliminating the differential remains to be seen.

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