Active Torque Vectoring Coming in Model 3 Performance?

[ZeroRider]

Based on the newly posted Model 3 Performance review from Automobile (Quick Drive: Tesla Model 3 Performance AWD):

"Go to the throttle smoothly on a fast corner exit and you’ll feel the lack of a true limited-slip differential as the inside rear tire lights up momentarily, before the new in-house Vehicle Dynamics Control (VDC—previously a supplier-sourced component) kicks in, grabs the brake, and forces the power to the outside wheel. Tesla says there’s an upgrade coming that will enhance this behavior by using active torque vectoring rather than the brakes to improve spirited (or track) driving performance. This new unofficial track mode is in development now, and not yet scheduled for release, but Tesla hopes to offer it to customers in the coming months.

While it's exciting news for enthusiasts if it turns out to be true, I'm not sure how they would pull off active torque vectoring with the open-diff design of Tesla's drive units. Anyone have further insight into this?

 

[e-FTW]

What you said! How does that work?
One possibility is that there might have been miscommunication between a very knowledgeable auto journalist and his Tesla handler.

 

[commasign]

Game changing if true. Would be crazy cool if power and/or regen could be asymmetrically distributed between left and right. But I’m skeptical as that would imply new and different hardware, something Tesla has been trying to avoid during production ramp up.

 

[e-FTW]

Game changing if true. Would be crazy cool if power and/or regen could be asymmetrically distributed between left and right. But I’m skeptical as that would imply new and different hardware, something Tesla has been trying to avoid during production ramp up.

Yeah, we need new unannounced hardware for that. Or two independent rear motors, so...
¯\_(ツ)_/¯

 

[Daniel in SD]

While it's exciting news for enthusiasts if it turns out to be true, I'm not sure how they would pull off active torque vectoring with the open-diff design of Tesla's drive units. Anyone have further insight into this?

They wouldn't. I suppose it's possible they put in an electronically controlled differential and just haven't implemented the code. But they're probably just talking about improving the performance of the brake based limited slip.

 

[ℬête Noire]

But they're probably just talking about improving the performance of the brake based limited slip.

Maybe they have enough power to spare to make it not suck, even? McClaren managed to make it work, but they had almost exactly double the HP to play with.

I wouldn't be surprised if you need the Performance Upgrade for it, too. So you don't eat the standard brakes up because this'll put huge amounts of energy (heat) into the brake pads/disks.

 

[Daniel in SD]

Maybe they have enough power to spare to make it not suck, even? McClaren managed to make it work, but they had almost exactly double the HP to play with.

I wouldn't be surprised if you need the Performance Upgrade for it, too. So you don't eat the standard brakes up because this'll put huge amounts of energy (heat) into the brake pads/disks.

McLaren also has carbon ceramic brakes. I’m sure there’s a lot of room for improvement in the current system though.

 

[ZeroRider]

I wouldn't be surprised if you need the Performance Upgrade for it, too. So you don't eat the standard brakes up because this'll put huge amounts of energy (heat) into the brake pads/disks.

Very good point about needing higher performance rear brakes in order for this to truly be effective for track driving. Based on what I'm seeing in some of the early M3P drives, it appears as though the rear brakes are especially beefy when compared to the standard Model 3, I think it's a good guess that Tesla is going the same open-diff route as McLaren

 

[30seconds]

Game changing if true. Would be crazy cool if power and/or regen could be asymmetrically distributed between left and right. But I’m skeptical as that would imply new and different hardware, something Tesla has been trying to avoid during production ramp up.

What hardware would be needed to implement asymmetrical regeneration based on steering input and motion sensors already in the car?

 

[Daniel in SD]

What hardware would be needed to implement asymmetrical regeneration based on steering input and motion sensors already in the car?

Two rear motors. It will be in the new roadster. And maybe the Model 4
It doesn’t seem like it would cost that much more since the motors could be half the size but I guess it would be silly for a mass market car.

 

[ℬête Noire]

Two rear motors. It will be in the new roadster. And maybe the Model 4
It doesn’t seem like it would cost that much more since the motors could be half the size but I guess it would be silly for a mass market car.

It also can be implemented within a [rather mechanically complex] differential. But it’d need to be something different than the RWD drive unit, this isn’t something easily missed on inspection.

 

[eSpiritIV]

I though that active torque vectoring either requires 4 motors, or two motors with a special differential. Not something they put in all AWD models? Rimac does this in their supercars with a special differential on eachmotor set
Rimac All Wheel Torque Vectoring | Rimac Automobili

 

[SSonnentag]

I though that active torque vectoring either requires 4 motors, or two motors with a special differential. Not something they put in all AWD models? Rimac does this in their supercars with a special differential on eachmotor set
Rimac All Wheel Torque Vectoring | Rimac Automobili

That's my understanding as well. Simulating ATV with brakes may help performance on the track, but will wreak havoc on the pads and rotors.

 

[ℬête Noire]

I though that active torque vectoring either requires 4 motors, or two motors with a special differential. Not something they put in all AWD models? Rimac does this in their supercars with a special differential on eachmotor set
Rimac All Wheel Torque Vectoring | Rimac Automobili

There is a third option:

It’s a sort of a variation on limited slip differential.

 

[ℬête Noire]

Simulating ATV with brakes may help performance on the track, but will wreak havoc on the pads and rotors.

"Wreak havoc" if you don't size them appropriately.

The key is to make sure your brakes can take the sizable amount of extra use. Because of the physics of how they work, you end up putting a lot of energy through the motor straight into the inside track wheel's brake pads & disk, which immediately gets converted into heat. If your brakes aren't up to that extra energy input bad things happen. Your brakes will start fading, pads/disk wears very quickly, etc. However if your pads & disks are up to it then it'll be something of an ok outcome.

It's quite likely it'll still be more brake usage than normal, and thus a lot more wear, but we are talking "track mode" which is normally an environment that implies heavier than normal wear, anyway. A couple things will help, first Tesla boosting regen strength in the mode, to take some of the typical de-acceleration load off the friction brakes. Second, the vectoring usage would focus (mostly?) on the rear wheels. Rear wheels tend to shoulder less of the work with de-acceleration braking, so normally are smaller than the front. By simply sizing the rear the same as the front you already have an inherent cushion for use of [rear] brake-based vectoring.

 

[juanmedina]

Very good point about needing higher performance rear brakes in order for this to truly be effective for track driving. Based on what I'm seeing in some of the early M3P drives, it appears as though the rear brakes are especially beefy when compared to the standard Model 3, I think it's a good guess that Tesla is going the same open-diff route as McLaren
View attachment 320029

I thought the rear rotors where supposed to be the same size as the base model 3 but with two piece rotors.

 

[Daniel in SD]

I'm sure there will be aftermarket limited slip differentials for the Model 3. Quaife makes one for the Model S.

 

[Canikony]

It also can be implemented within a [rather mechanically complex] differential. But it’d need to be something different than the RWD drive unit, this isn’t something easily missed on inspection.

How could the motor be regenerating power from one wheel while propelling the other? That sounds physically impossible.

 

[ℬête Noire]

How could the motor be regenerating power from one wheel while propelling the other? That sounds physically impossible.

I don't understand how the question of having that ability is connected to this topic? Could you help by explaining the connection you see?

 

[ZeroRider]

I thought the rear rotors where supposed to be the same size as the base model 3 but with two piece rotors.

Yes, I believe the rear has the same size rotors as the standard Model 3 (although a different rotor type), but check out those calipers, they're huge!