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Model X with Dual Motor All-Wheel Drive. Does this mean that this car will have 2 identical motors, so same motor front as rear?

The main question is will these 2 electric motors be identical (and therefore, will they have the same capacity) or will they not be identical (and therefore, if they are different, will they not have the same capacity)? What will it be? Does anyone know anything about this?

cprenzl | 31 January, 2013

Go watch the Model X reveal. Should answer that better but, short answer: No

Benz | 31 January, 2013

@ cprenzl

I have just been watching the video of the reveal of the Tesla Model X. I have been listening to what Elon Musk has told about the Dual Motor AWD. The only interesting thing about the Dual Motor AWD that he mentioned was that "you can dynamically shift power from front to rear, depending upon what has got the most traction". But he did not say anything about the type of those two motors, and if they were identical or not. So, after having watched this video of the release of the Tesla Model X, my question has not been answered. But I still am interested why your answer is: "No"?

llehctim | 31 January, 2013

"The second motor enables more than all-weather, all-road capabilities: it increases torque by 50%."

I don't know much about the science of torque versus wattage of motors, but this suggests to me that the front motor is half as strong.
Alternatively the rear motor could be smaller for the AWD than the 2WD and still give rise to that statement.

Under violent acceleration (or steep uphill) I expect most of the weight to be on the rear wheels. Hence if Tesla is optimizing for 0-60 times then I would have the expectation of the weaker front motor.

My wild guesses/speculation as to what Tesla would use to maximize reuse from Model S of motors and inverters... assuming X is ~10% heavier than S

Model S motor/ | 0-60 | Model X | 0-60
inverter | | |
---------------------------------------
S 60 5.9 60 6.5
S 85 5.6 85 opt1 6.2 (likely)
P 85 4.4 85 opt2 4.9 (unlikely)
S85 mot/inv + weak front 85 AWD 5.6*1.1*2/3=4.1... with a weaker inverter maybe makes this one ~4.4
P85 mot/inv + weak front P85AWD 4.4*1.1*2/3=3.3 !

The 2/3 is based on the 50% extra torque statement.
Tesla was also conservative about S 0-60 times from what we see users/reviewers reporting.

Note with the 4WD options I have no idea how the inverters would work (ianaee) and these may be limited by the batteries instead of inverters/motors.

Timo | 31 January, 2013

It is also possible that battery just can't deliver enough power that two motors can get twice as much torque, but still have twice as much torque when not used at full power.

Or alternatively, if the torque is measured at the wheels, then reduction gear is lower: instead of "fixed gear with 9.73:1 reduction ratio" you have "fixed gear with 7.3:1 reduction ratio". That would allow higher top speed because torque drop and the absolute limit of RPM comes in play at higher speeds.

600Nm*9.73 = 5838Nm, 2*600Nm*7.3 = 8760N, 8760Nm/5838Nm = 1.50.
5838Nm /2 = 2919Nm/wheel, 8760Nm /4 = 2190Nm/wheel (still happily burns rubber with TC off).

Truth is probably somewhere between those two.

Benz | 1 February, 2013

Can we forward this question to the people from Tesla Motors? Maybe they can shine some more light on this matter?

RDoc | 4 February, 2013

Looking at the Model X platform photo on the Tesla site, the one with no body, it looks to me like the front motor is half the rear. The rear motor actually has 2 motors feeding the power train. It looks to me like the front motor is just one of those.

Benz | 4 February, 2013

I have seen that photo particular photo. But I do not have the knowledge to say something like that.

Brian H | 4 February, 2013

No, that "2nd motor" in the rear is actually the PEM, the controller and DC/AC inverter for the motor(s). Only one is needed to handle the front and rear.

Benz | 5 February, 2013

@ Brian H
So, do you know the answer to my question (are both motors identical or not)?

Brian H | 5 February, 2013

No, deep proprietary corporate secret. Occam's Design Razor suggests the differences would be in gearing and the controller, though.

Brian H | 5 February, 2013

Occam's Design Razor: Do not multiply devices and design details beyond necessity.

scottf200 | 6 February, 2013

This video indicate they would be used for different purposes as well.

Benz | 6 February, 2013

I have watched the video. And I have understood that with a second motor you add more mass to the EV. But this does NOT result in a lower range!!!! That's very interesting. And the two motors will not always be working equally hard. They will be working individually depending on the several different driving situations/conditions. That's also very interesting to know. I think that I am slowly getting more and more positively attracted to this dual motor AWD option. It sounds great, but still I would like to test drive a Tesla Model X AWD. Not before September, I am afraid.

Brian H | 6 February, 2013

The motors are light, about 130 lb for the single MS motor. The two in the AWD could be each lighter than that. IAC, not significant in the total car weight ... a rounding error, basically.

Timo | 6 February, 2013

My cautious estimate for entire drivetrain minus battery is 150kg, so with 150kg added to already over 2100 kg car would be adding about 7% weight. That would result in about 2-3% less range, which is small enough that efficiency difference caused by load difference between two and one motors could negate that entirely.

Brian H | 6 February, 2013

Adding one motor does not duplicate the drivetrain. I doubt even 150 lbs. would be added.

Vawlkus | 6 February, 2013

Umm..... actually Brian, it WOULD duplicate the drivetrain, or else the second motor wouldn't be able to do very much :P

Don't forget, the front wheels have to pivot, so the drivetrain must be modified to allow for that steering. If anything, I think the front drivetrain would weigh a little more than the rear one does, just for that alone.

Timo | 6 February, 2013

Also heavy duty cabling (around 1000A cables are not light) and liquid cooling would need to be added in addition to more complex axle system. Only thing that doesn't add itself there is the PEM assuming single PEM can handle two motors. If not then that too would need to be added.

Brian H | 6 February, 2013

Both motors would be able to be lighter, and the photo referred to by RDoc above shows no PEM up front. The current motor reputedly weighs 130 lb. So where is this 150 kg. (330 lbs) coming from? That's at least 200 lb. too high.

Benz | 6 February, 2013

@ Timo

"About 2-3% less range" is good.

But there sure is another thing: Air Drag. The Tesla Model S has an air drag figure of 0.24 (that is extremely low, for this kind of vehicle). We all know that the Tesla Model X is less earodynamic than the Tesla Model S. And this is also going to result into a lesser range. But will that figure also be around 3% or is 10% more likely. I really do not have any clue on this issue. But I sure would like to know more about it. Anyone?

Timo | 7 February, 2013

Brian H; the motor alone is only small portion of the whole drivetrain assembly. I would assume transmission casing alone weights 50lbs, structures required to fix that motor in place (so that torque doesn't rip it loose), axles, cables, liquid cooling fluids and tubes would easily add up to 100 lbs if not more. Add in 130 lbs from the motor and you have that around 300 lbs.