New AWD Motor Info from fueleconomy.gov

[Krash]

Agree on hitting max current/ torque (traction?) before hitting max power.
But you lost me here:

It won't feel any quicker, since most feel "quickness" in the torque. And when the torque is the same but just applied longer in the AWD before it starts to level off at max power, most won't notice.

If we assume the pack is the same on all LR3s, then the peak output power of the pack (before SW limiting) is the same for all motor configurations. As such, at the lower RPM, the limit is the current the motor can handle (torque). So why wouldn't the AWD have higher total torque than RWD given that the front motor can provide torque beyond what the rear motor can (up to the max pack power limit)?

Except the limit is the torque limit first and the power limit second. The car will never reach the 1200A current limit since the power will be limited well below 500kW (1200A * 400v). If you increase the torque much more AND keep that level of power the car is faster than 3.5 seconds 0-60.

I'm guessing the front motor is setup for low end power more than high end for a couple reasons: Tuning it toward the low end improves the effect of regen. Most driving will be done at sub 100 MPH, so that is the normal useful power band for drivers. Under launch, the power split due to tractions will be, what like 40/60? So for 0-60 the sweet spot is a front motor with 2/3 the torque of rear. Of course, during braking/ regen the opposite is true.

I am betting they did all that optimization for the RWD.

 

[Krash]

Can you lay out for me, roughly, the math and inferences used to get the gearing ratio of each drive unit from that?

Sure. But this and the referenced physics threat are better as they have commentary from real physicists before and after. If you are wondering how we know the split for front and rear drive units, we aren't that sophisticated so we just average. On the CANBus you know the split, but you can get the actual per motor torque on CANBus so you don't need to estimate it.

 

[mongo]

Except the limit is the torque limit first and the power limit second. The car will never reach the 1200A current limit since the power will be limited well below 500kW (1200A * 400v). If you increase the torque much more AND keep that level of power the car is faster than 3.5 seconds 0-60.

Ah, so you are saying Tesla is artifically limiting the acceleration, not that AWD can't provide more acceleration?

 

[FlyNavy01]

I think your numbers are hugely optimistic.

1/4 mile trap speed of 126.1mph is faster than the current P100D record holder with over 400lbs stripped from the interior... That's just not happening.

Also 0-60mph in 3.09seconds is not possible with the current battery pack power limitations. I think the fastest we'll see is low 3.4's maybe high 3.3's under ideal conditions unless they uncork it past it's 5C pack discharge rate.

 

[wallet.dat]

147kW + 211kW = 358kW for the Performance model - or 480HP - that's more than the most powerful BMW M3 CS with 453HP. And I'm guessing those are conservative numbers... This is gonna be fun.

Probably has a little bit more torque too

 

[ℬête Noire]

If you are wondering how we know the split for front and rear drive units, we aren't that sophisticated so we just average.

That's where I'm lost on how you could determine from the CAN bus the individual gear ratio of each drive unit (which is what I'm looking for here, maybe my post wasn't clear on that?). I had understood that you used the gear ratio (that you determine prior) in combination with the info off the CAN bus to do the calculations.

Maybe I need to re-read closer in that thread.

P.S. I'd be somewhat surprised if the front was geared for higher speed in the Model 3, as it's the one that [assumedly] will go to sleep during level cruising at highway speeds?

 

[mongo]

P.S. I'd be somewhat surprised if the front was geared for higher speed in the Model 3, as it's the one that [assumedly] will go to sleep during level cruising at highway speeds?

If meaning geared for higher road speed, that would help during torque sleep since the reversed radio means less drag due to motor/rotor/gear speed along with less inertia multiplication (square of the gear ratio).

 

[ℬête Noire]

If meaning geared for higher road speed, that would help during torque sleep since the reversed radio means less drag due to motor/rotor/gear speed along with less inertia multiplication (square of the gear ratio).

Good point, I hadn't thought of it that way. Since the sleep can't really be perfect (especially over time as the motor naturally becomes somewhat magnetized with use). It is strange though, then, that the Model S did have the higher ration in the front even though it was always the rear motor that sleep (in the P).

 

[Krash]

I think your numbers are hugely optimistic.

1/4 mile trap speed of 126.1mph is faster than the current P100D record holder with over 400lbs stripped from the interior... That's just not happening.

Yeah, If the SWPM motor torque is already pegged in the RWD then the induction motor will need to be geared for low speed power and as a consequence there will be this huge drop in power above 60 mph.

But if I were Tesla I would have built that rear motor for half the rear roadster too and left some room in it for the added torque, so that the induction motor could prevent the power drop at the high end.

Also 0-60mph in 3.09seconds is not possible with the current battery pack power limitations. I think the fastest we'll see is low 3.4's maybe high 3.3's under ideal conditions unless they uncork it past it's 5C pack discharge rate.

I haven't figured downforce, but you don't need 1500A to beat the P100D. All you need is a second motor geared to not have the power drop from Field Weakening or BackEMF. That and a smaller frontal surface area, better drag coofecient and less weight.

Frankly the biggest reason we wouldn't see that kind of performance is because of what it would do to P100D sales, unless of course there is a P120D around the corner.

 

[ℬête Noire]

Good point, I hadn't thought of it that way. Since the sleep can't really be perfect (especially over time as the motor naturally becomes somewhat magnetized with use). It is strange though, then, that the Model S did have the higher ration in the front even though it was always the rear motor that sleep (in the P).

*facepalm*

In the Model S P which was sleeping the rear motor (EDIT: cruising with the front motor) because the larger, older generation motor wasn't as efficient. And the result is the Model S P has notably lower eMPG than the D. So it is quite possible they slept the (EDIT:rear, driving with the front,) in spite of it having the higher ratio gearing than the rear. OK, that's starting to make sense.