0-60 of ct dual fs vs model x dual

[JBee]

Why when I can just ask you? It doesn't matter that much anyways, already ordered the dual

To answer your question on why the repeatability of acceleration differs between the MX and CT:

The MX uses a different battery cell technology and also has a smaller capacity battery pack than the CT, meaning that the MX pack heats up faster than the CT pack when put under heavy acceleration loads, which means it thermally throttles subsequent acceleration attempts more than a CT. Depending on your MX, you might also have a lesser capable cooling system as well in comparison to a CT.

This only applies for if you do one acceleration run after another without enough time inbetween for the system to recover.

Between traffic lights you probably won't notice it until your SOC reduces.

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[JBee]

how about a poster who is simultaneously cracking grammar slights, while consistently misusing ellipses?




PS: Australians don’t need to know the difference between “would of” and “would have” because spoken in Aussie they sound identical

Hey!

Nobody is perfect, not even us Aussies!

I often get asked where in South Africa I'm from, because my German accent keeps leaking through. Joke is I'm Aussie born, but often speak German at home, so there's always something leaking through either way.

 

[Gurule92]

I noticed you said you had a 17 ms plaid. That's not a thing just so you know. But model X used to have a 4 something for dual motor but then the performance motors became the dual and the plaid became the performance. Basically.

 

[PilotPete]

• AWD Tri/Beast: front locker + torque_vectoring
• AWD Dual with front & rear lockers

And the reason the CB doesn’t have real diff locks? It doesn’t have a single drive source to both wheels. To compare the AWD to the CB and think the AWD is somehow better would be like me saying my old Land Rover was better than an AWD CT because the LR had a locking center diff.

The CB doen’st need, nor would it benefit from a locking rear diff as the left and right rear are powered independently! In the AWD, if there is traction on the left rear and not the right rear, when the diff is locked, both wheels turn at the same rate. The left and right rear turn at the same speed and all the power is available to the single left rear tire.

On the CB, all the power (of a single motor) is available to that left rear all the time. And the computer controls each motor independently. They bother are equally capable of getting out of the same place at the same time.

 

[swinefeaster]

I noticed you said you had a 17 ms plaid. That's not a thing just so you know. But model X used to have a 4 something for dual motor but then the performance motors became the dual and the plaid became the performance. Basically.

Maybe I got the model name wrong or the year but it was twice as fast off the line compared to my mx dual, and the interior was old and janky and the touch screen was vertical and the steering wheel was round . It was a loaner from the Tesla service center.

 

[swinefeaster]

And the reason the CB doesn’t have real diff locks? It doesn’t have a single drive source to both wheels. To compare the AWD to the CB and think the AWD is somehow better would be like me saying my old Land Rover was better than an AWD CT because the LR had a locking center diff.

The CB doen’st need, nor would it benefit from a locking rear diff as the left and right rear are powered independently! In the AWD, if there is traction on the left rear and not the right rear, when the diff is locked, both wheels turn at the same rate. The left and right rear turn at the same speed and all the power is available to the single left rear tire.

On the CB, all the power (of a single motor) is available to that left rear all the time. And the computer controls each motor independently. They bother are equally capable of getting out of the same place at the same time.

You're triggering my fomo

 

[cvalue13]

And the reason the CB doesn’t have real diff locks? It doesn’t have a single drive source to both wheels. To compare the AWD to the CB and think the AWD is somehow better would be like me saying my old Land Rover was better than an AWD CT because the LR had a locking center diff.

The CB doen’st need, nor would it benefit from a locking rear diff as the left and right rear are powered independently! In the AWD, if there is traction on the left rear and not the right rear, when the diff is locked, both wheels turn at the same rate. The left and right rear turn at the same speed and all the power is available to the single left rear tire.

On the CB, all the power (of a single motor) is available to that left rear all the time. And the computer controls each motor independently. They bother are equally capable of getting out of the same place at the same time.

now you’ve stepped in it with the experienced offroad crowd


They’ll explain all day that physical lockers are and will always be necessarily better than software-controlled traction

The more mechanically inclined will do a pretty convincing job of it

 

[scottf200]

And the reason the CB doesn’t have real diff locks? It doesn’t have a single drive source to both wheels. To compare the AWD to the CB and think the AWD is somehow better would be like me saying my old Land Rover was better than an AWD CT because the LR had a locking center diff.

The CB doen’st need, nor would it benefit from a locking rear diff as the left and right rear are powered independently! In the AWD, if there is traction on the left rear and not the right rear, when the diff is locked, both wheels turn at the same rate. The left and right rear turn at the same speed and all the power is available to the single left rear tire.

On the CB, all the power (of a single motor) is available to that left rear all the time. And the computer controls each motor independently. They bother are equally capable of getting out of the same place at the same time.

Yes, all that is clear to most. The Rivian has a Quad motor version with four independent motors on each wheel. It is a matter of programming and the power of each motor. In the case of the Quad Rivian there have been off-road scenarios that people have videoed where essentially 1 wheel was required to get it out a teetering rocky situation while climbing and *their* 1 motor was inadequate to get the heavy vehicle up the "steep" slope.

Not sure if you follow the Rivian Quad or other pickup BEVs as I recall you not even wanting a "pickup" but a versatile generic sports and utilitarian vehicle.

 

[SentinelOne]

CB is 1 physical locker (for the off-road crowd) and 1 virtual locker + TV (for the rest of us) = best of both worlds!

 

[JBee]

now you’ve stepped in it with the experienced offroad crowd


They’ll explain all day that physical lockers are and will always be necessarily better than software-controlled traction

The more mechanically inclined will do a pretty convincing job of it

And the reason the CB doesn’t have real diff locks? It doesn’t have a single drive source to both wheels. To compare the AWD to the CB and think the AWD is somehow better would be like me saying my old Land Rover was better than an AWD CT because the LR had a locking center diff.

The CB doen’st need, nor would it benefit from a locking rear diff as the left and right rear are powered independently! In the AWD, if there is traction on the left rear and not the right rear, when the diff is locked, both wheels turn at the same rate. The left and right rear turn at the same speed and all the power is available to the single left rear tire.

On the CB, all the power (of a single motor) is available to that left rear all the time. And the computer controls each motor independently. They bother are equally capable of getting out of the same place at the same time.

It's just physics.

Torque vectoring is reactive. (So is traction control, but this can't be modulated with hydraulic brakes as fast as an electric motor can electronically)

Diff lock is passive but real time.

Simple thought experiment:

1) Imagine each peice of a tank track moving independently from eachother and at different speeds to eachother, and producing forwards momentum at different times to eachother.

2) Then imagine a tank track, where each peice of track moves at the same time with the same force, with the same speed and keeps momentum in sync between all peices.

Which one is better?

It depends...

For slow speed in a straight line, over uneven terrain with variable amounts of traction it's of course Lockers in 2)

BUT.... if you are already driving, and already have lots of wheel rpm and you want to manage wheelspin, it's torque vectoring, because this also allows you to change and modulate left and right side rpm, which a standard fixed locker can't do. There are however torque vectoring diffs as well, and they have been around for decades, so one of those could do similar to a TM.

The other problem with torque vectoring is if traction changes between sides when rolling downhill. A differential naturally balances motor braking torque between left and right. That is to say it "allows" wheel slip depending on the level of traction on each wheel, which creates a controlable decent. Having a diff lock on, or torque vectoring on, with synchronised side to side rpm, would mean that one side would break traction, which would introduce unwanted steering yaw.

In a Lucid video they discussed how fast they can modulate electric motors to improve traction for launch control. Turns out they sample a few hundred times a second, but can only effectively modulate motor output 25 times per second (25Hz). This means in the 2 seconds it takes a Lucid to get to 60, it does around 50 optimisations.

Compared to a diff lock and driveshaft setup, that's nothing, as they can oscillate in the kHz range without an issue.

So it really does depend on the circumstances, conditions, and vehicle speed.

 

[scottf200]

In a Lucid video they discussed how fast they can modulate electric motors to improve traction for launch control. Turns out they sample a few hundred times a second, but can only effectively modulate motor output 25 times per second (25Hz). This means in the 2 seconds it takes a Lucid to get to 60, it does around 50 optimisations.

I wonder what Teslas are like since they have always been known for excellent traction control and hence great track performance / 0-60 / etc. As well the CarWow video was doing the CT 'racing' on dirt roads. I believe it was in one of Kyle's videos where he indicated that some (all?) the traction control logic was in the motor/gear housing (ie. closer) vs logic back at the cars main computers ('travel time' added to delays (Hz)). CT giga speed network may have made this less of an issue but it was on all the other Tesla cars using more traditional car 'networking'.

 

[JBee]

I wonder what Teslas are like since they have always been known for excellent traction control and hence great track performance / 0-60 / etc. As well the CarWow video was doing the CT 'racing' on dirt roads. I believe it was in one of Kyle's videos where he indicated that some (all?) the traction control logic was in the motor/gear housing (ie. closer) vs logic back at the cars main computers ('travel time' added to delays (Hz)). CT giga speed network may have made this less of an issue but it was on all the other Tesla cars using more traditional car 'networking'.

So torque vectoring would be done in the two motor controllers themselves.
The motor controllers/inverters actually have to synchronise magnetic polarity with rotor position to a fraction of a degree already, so they already need to know rotor position for this, and so wheel rpm is just that times the gear ratio.

It would also be able to use the current at each step to determine wheel torque. In the case of two motors in the rearper wheel, and otherwise per single motor axle.

So that means the electric motor controller would essentially be telling the brake controller what to do.

The difference here though is that torque vectoring (TV) would be controlled by the motor inverter alone, and requires only switching of the electromagnetic feilds, and can be done much faster than traction control that is physically switching hydraulic brake valves.

 

[scottf200]

So torque vectoring would be done in the two motor controllers themselves.
The motor controllers/inverters actually have to synchronise magnetic polarity with rotor position to a fraction of a degree already, so they already need to know rotor position for this, and so wheel rpm is just that times the gear ratio.

It would also be able to use the current at each step to determine wheel torque. In the case of two motors in the rearper wheel, and otherwise per single motor axle.

So that means the electric motor controller would essentially be telling the brake controller what to do.

The difference here though is that torque vectoring (TV) would be controlled by the motor inverter alone, and requires only switching of the electromagnetic feilds, and can be done much faster than traction control that is physically switching hydraulic brake valves.

Because there are independent motors in the rear on the AWD Tri-beast did/can Tesla use 'regen braking' instead of the physical brakes for the logical "traction control"?

I also didn't know if the type of motor played a factor in any of this?
[oddly in contrast to the Tri-beast, the S/X plaid use permanent on the two rears per the manual]

 

[LiveFreeOrDieBob]

And the reason the CB doesn’t have real diff locks? It doesn’t have a single drive source to both wheels. To compare the AWD to the CB and think the AWD is somehow better would be like me saying my old Land Rover was better than an AWD CT because the LR had a locking center diff.

The CB doen’st need, nor would it benefit from a locking rear diff as the left and right rear are powered independently! In the AWD, if there is traction on the left rear and not the right rear, when the diff is locked, both wheels turn at the same rate. The left and right rear turn at the same speed and all the power is available to the single left rear tire.

On the CB, all the power (of a single motor) is available to that left rear all the time. And the computer controls each motor independently. They bother are equally capable of getting out of the same place at the same time.

When you have a mechanical locker, the wheels on either side of the locker are guaranteed to spin the same speed no matter how much traction is on either wheel, even if one wheel catches or loses traction instantly. Or the next step up would be a Torsen diff, where you can have a difference in the speed of each wheel, for example due to turning through an inscribed arc, but both wheels are getting power no matter what - even if one has zero traction.

Purely from an off-roading perspective, while separate motors theoretically can be almost as a good as a mechanical locker, they are practically speaking never "better". Whether it *is* as good as a locker comes down almost exclusively to software and to some extent sensors.

The mistake almost all manufacturers make when it comes to AWD is to assume that the goal is to avoid slip. Which is fine 90% of the time - under certain conditions like icy roads, avoiding slip at all costs by either braking individual wheels and/or cutting engine power is fine and will help keep the car on the road. Picture a soccer mom driving around in 33 degree weather who hits a patch of ice.

But in deep snow, mud, or rock crawling, avoiding slip is NOT the goal - the goal is to keep all four tires moving at a similar speed so each wheel is contributing some drive force even if it's slipping. And that speed should be controlled by the driver through the accelerator pedal. There should be no braking of wheels and no cutting of engine power when you're rock crawling or driving in deep snow or mud - cutting power to any wheel lowers your momentum and gets you stuck.

So whether the CB is as good as the CT AWD's lockers off road will largely depend on whether the traction control calibration's goal was to avoid slip or to keep all four wheels turning at around the same speed. The video that came out a couple months ago of the CT trying to get up some "steps" in an offroad terrain park seemed to indicate that the traction control was tuned to eliminate slip, which is not a good sign. But I'm hopeful that they were just gathering data to calibrate the traction control system, or were testing the rear-steering's impact on offroad running.

 

[LiveFreeOrDieBob]

I wonder what Teslas are like since they have always been known for excellent traction control and hence great track performance / 0-60 / etc. As well the CarWow video was doing the CT 'racing' on dirt roads. I believe it was in one of Kyle's videos where he indicated that some (all?) the traction control logic was in the motor/gear housing (ie. closer) vs logic back at the cars main computers ('travel time' added to delays (Hz)). CT giga speed network may have made this less of an issue but it was on all the other Tesla cars using more traditional car 'networking'.

For true torque vectoring you need steering angle as an input - for example if you have the squircle cut to the left, the right/outside motor should be turning slightly faster than the left/inside motor.

So as you are implementing your torque vectoring, you might be able to do it right at the motor controllers, but you still need to know what the commanded steering wheel angle is. You can almost certainly poll the current steering angle off the ethernet ring at a much lower frequency than what you need from the the VSS' (Vehicle Speed Sensors) since you won't be turning the steering wheel that quickly, but you definitely need the steering angle as an input to the calculation of what speed to command at each wheel.

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