Raven doesn't add up

[Simon21]

I'm trying to figure out how this adds up.

Model 3 is lighter than S
Model S is faster than 3

Difference has to be with the motor, otherwise the lighter car would be faster. But when model S gets the 3 motor, they claim it's faster than before? If it gets a slower motor, how is it faster?

Please note: Faster in this context refers to acceleration, which is the way it is used by the majority in colloquial talk

 

[zanary]

I believe you can pull more amps from the P100D battery, couple that with the dual motors, and you do get a quicker acceleration than the Model 3 Performance. I'll let others provide far more technical details.

 

[iqless]

Also it's almost certain that Tesla is limiting the performance of the P3D in order to not get into Model S territory.

 

[Cheburashka]

Also it's almost certain that Tesla is limiting the performance of the P3D in order to not get into Model S territory.

Exactly.

 

[jdw]

The 100kWh battery has almost twice as many cells as the 75kWh Model 3 battery and operates at a nominal 400V instead of 350V and can deliver more power to the motors (very roughly 575kW vs 325kW). Tesla motors are battery and/or inverter constrained. The Performance S motor power is rated at 762HP, but the battery power is rated at 605HP as an example.

Even with the different Model S cars you can see this - a 60kWh Model S will be slower than a 100kWh Model S as a result of 2 less battery modules (less current) and corresponding lower nominal operating voltage.

Model 3 74kWh Pack: 4416 cells in groups of 46 cells per brick with 96 bricks in 4 modules = 350V and "over" 300kW - around 1000 amps*
Model S 102kWh Pack: 8256 cells in groups of 516 cells in 16 modules = 400V and 575 kW - around 1500 Amps

The Model 3 also has excellent inverters which make very efficient use of battery power - these inverters were brought over to the Raven, along with a PMSR front motor similar to the rear motor of the 3, all part of the speed and efficiency improvements you see with Raven models.

If you get into the Performance L cars, the rear motor alone is almost as powerful as the two motors in the 3 combined.

Finally, all this is under software control, which allows for things like Ludicrous mode, P3D's vs LR AWD 3's as well as uncorkings or arbitrarily limiting some cars if you're inclined to think that way ...

*hard to find exact info - Wikipedia has all this info for the S, but the 3 info is spotty.

 

[ucmndd]

I'm trying to figure out how this adds up.

Model 3 is lighter than S
Model S is faster than 3

Difference has to be with the motor, otherwise the lighter car would be faster. But when model S gets the 3 motor, they claim it's faster than before? If it gets a slower motor, how is it faster?

Please note: Faster in this context refers to acceleration, which is the way it is used by the majority in colloquial talk

This might make perfect sense if the motors were drawing power from the same source. They’re of course not. The P100 battery can deliver far more current than the P3.

 

[ucmndd]

Also it's almost certain that Tesla is limiting the performance of the P3D in order to not get into Model S territory.

I don’t think so. It’s all about the battery.

 

[Ostrichsak]

It's almost as if the two cars are entirely different and one was made to be a budget entry-level car and the other... wasn't.

 

[Saghost]

The Model 3 motor added to the Project Raven cars is the front motor on them, the rear motor on the performance 3.

On the Performance Ravens, most of the raw power to catapult them to speed comes from the big rear induction motor.

Weight transfer during acceleration means that the front motor doesn't have the traction to contribute all that much to the effort.

The Stats on the Raven quarter mile video show 2/3 of the peak power goes to the rear motor, and I think that's fairly typical throughout the speed range on hard accelerations for a Raven.

Not entirely sure why they are fractionally faster than the past versions - the lower rolling resistance of the new wheel bearings?

Better control of the car's stance and weight transfer from the adaptive suspension?

Minor tweaks to the Rev E battery pack allowing a little more peak power?

I think that the PMSR front motor is incidental to the acceleration improvement.

 

[Chaserr]

The model S has more cells. More cells can deliver more power per cell without creating more heat (each horsepower is distributed among more battery).

Ludicrous launches deliver 1700 amps. The Model 3's battery can't deliver that many amps. S battery has 8256 cells to share the work, Model 3 LR battery has 5000-ish cells.

Remember 691-gate? Tesla claimed teh P85D had 691 horsepower but it didn't? 85 batteries have 7000-ish cells and can't deliver 691 horsepower safely. 100 packs can, they have more cells and so they heat up less and can make more power.

Raven has a more efficient front motor now - it gets more range, but more efficiency also means it loses less horsepower to drivetrain losses and is faster too. Ravens also have a new 100 battery that charges faster, so they have internal changes that allow higher input and probably also higher output - the faster charging might even mean better cooling and heat is what defines the battery's safe limits.

 

[Simon21]

If Raven charges faster, then why is the max something like 48A for level 2 vs 72 A for the older ones?

 

[DukeofURL]

If Raven charges faster, then why is the max something like 48A for level 2 vs 72 A for the older ones?

They charge faster at Superchargers (mostly due to larger gauge cabling from the port, but perhaps also some battery changes - there was a new revision). The lower AC charging rate at home was, like many regressions, done to save money and streamline assembly line operations.

 

[Saghost]

If Raven charges faster, then why is the max something like 48A for level 2 vs 72 A for the older ones?

Tesla made a strategic decision to change all the chargers to use the 16A modules they use for the model 3. They decided that no one needed 72A charging, so they don't offer it anymore.

Note that this isn't a Project Raven change - they discontinued the 72A charger version in December of last year. Before that it was standard on 100 kWh cars I believe.

 

[RayW]

Also it's almost certain that Tesla is limiting the performance of the P3D in order to not get into Model S territory.

1,000A vs 1,500A.... if anything, Tesla is limiting the performance of the Raven

 

[iqless]

1,000A vs 1,500A.... if anything, Tesla is limiting the performance of the Raven

Hey, please don't try to lamely put science between me and my wild speculations that are based on nothing!!!

 

[Chaserr]

Elon once said the P3D will get Ludicrous, and of course it's intentionally limited. Whether that happens or not, he probably saw it in testing and it could happen, maybe after they release the MCU App Store they said we would get years ago. They limit power to a warranty friendly failure rate, it can be increased beyond those limits - that's why Ludicrous enabled cars warn you it can cause accelerated wear to motor and battery when you turn it on. You paid to cover that wear under Warranty when you bought it.

Raven cars now offer Ludicrous for less added $warranty spent on purchase price, which either means Ludicrous causes less wear than they thought originally or Raven has a higher performance ceiling than we are seeing.

 

[jdw]

So, after looking around trying to find more info, it seems that the most accurate measurement for comparison is the combined torque the cars can produce. Doesn't fully answer why, but if you look at the torque and the weight of the cars, the 0-60 speeds fall into place. All of these cars are limited by their batteries as there is not enough power to drive both motors to their maximum, which points out how Tesla dynamically manages power in these cars.

Model 3 AWD - 376 lb-ft (4.4 sec)
Model 3 P - 471 ib-ft (3.2 sec)
Model S LR - 487 lb-ft (3.6 sec)
Model S P - 687 lb-ft (2.2 sec)

A short section of JB Straubel's blog post on dual motors, batteries and inverters from 2015 which explains why it is useful that the motor power exceeds the battery power:


With the shaft horsepower coming out of the motors the situation is not always as simple as front + rear. As we have pushed the combined motor horsepower higher and higher, the amount of times where the battery chemical horsepower is lower than the combined motor horsepower has increased.

Also, the all wheel drive system in the dual-motor cars distributes available electrical horsepower to maximize torque (and power) in response to road grip conditions and weight transfer in the vehicle. For instance, during hard acceleration, weight transfers to the rear of the vehicle. The front motor must reduce torque and power in order to prevent the front wheels from spinning. That power is fed to the rear motor where it can be used immediately. The opposite happens when braking, when the front motor can accept more regenerative braking torque and power.

 

[brkaus]

Faster performance means things break more. Sure, the components may be capable of more, but it has to be able to do it safely. Heck, they may have limited the model 3 a bit just so 1 out of 100 launches don't melt the wiring harness or break a half shaft. That really doesn't mean it was "nerfed"

You can buy after market chips for many cars that increase the performance. Some make significant increases. But those chips also void the warranty if the increased power caused the problem.

 

[TIppy]

If you watch the video up thread, you can see that the peak horsepower on the raven is now about 716 hp. At that peak, the efficiency is about 95 percent, so considerably more of the battery hp is going to the motors. My P90DL was only 82.5 percent efficient at max power. Also they're using about 95 percent of the combined hp of the two motors.

 

[mongo]

Difference has to be with the motor, otherwise the lighter car would be faster. But when model S gets the 3 motor, they claim it's faster than before? If it gets a slower motor, how is it faster?

Model 3: PMSR motor in the rear, small AC induction motor in the front
P100 S: P level Large AC induction in the rear, PMSR in the front.
Relative power output:
Large AC > PMSR > Small AC

The 100kWh battery has almost twice as many cells as the 75kWh Model 3 battery and operates at a nominal 400V instead of 350V and can deliver more power to the motors (very roughly 575kW vs 325kW).

Cell count does not matter directly since the cell volumes are different. Chemistry is the same so kWh is a valid comparison. 100 is 33% more available energy (and power) than the 75kWh not nearly double. The voltages are also the same:

Model 3 74kWh Pack: 4416 cells in groups of 46 cells per brick with 96 bricks in 4 modules = 350V and "over" 300kW - around 1000 amps*
Model S 102kWh Pack: 8256 cells in groups of 516 cells in 16 modules = 400V and 575 kW - around 1500 Amps

Model S/X 100kWh and Model 3 75kWh packs are each 96s, both have the same voltage. The 75kWh S/X packs had a lower voltage due to 14 modules instead of 16, 84s.
Also, the 3 has two different sized modules, long in the center and shorter on the edges. The SR 3 is also 400V 96s.