I just found the original thread with Scott Francis' note that "Performance in Blue, Dual motor in Red. lower graph of green and yellow are both cars in chill mode." So this is good for AWD and Performance. Has anyone seen any recent dynos for RWD? MPP did theirs when they first picked it up and then did the SR+ a few weeks ago, but I haven't seen any RWD since the first power bump.
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What will be the new HP numbers for AWD and P after 12.4?
- Thread starter Swampgator
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gavine
Petrol Head turned EV Enthusiast
AlanSubie4Life
Efficiency Obsessed Member
No, these numbers are translated back to the "crank," but how accurately that is done and what the assumptions are is unclear - specifically there is no way to know whether losses were estimated or not with this data. Obviously there has to be something like 4000lb-ft of torque to the axles to get the ~0.86g of acceleration with a wheel radius of 13.16/13.23 inches - you need 3700 lbs of force applied to the ground.
All these numbers are dependent on the person entering the data providing the exactly correct final reduction, the right wheel radius/diameter, and it's not clear to me whether there is a parameter to include drivetrain losses in the Dynojet setup.
In any case the drivetrain losses are likely not nearly as high as 15-20%. It's less than 10%.
I'd recommend avoiding reading too much into the actual peak numbers on these plots, and looking at it more as a general picture of how things work above ~3500rpm (obviously the low RPM data (below 3000rpm) is totally, completely incorrect - torque only starts dropping below around 500rpm; below 5mph).
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Knightshade
Well-Known Member
But...it's not one.
There's no transmission as such- there's no torque converter or clutch to lose power to... there's just a single, fixed, reduction gear. Losses aren't 0, but they're much lower than an ICE car.
I believe that dyno was done in November, 2018 where the 1st power increase was released in March, 2019.
the most abused quote in motoring, and an affront to both physics and english
MichaelP90DL
Active Member
I don't think Mr. Shelby held a doctorate in physics. Or even in English physics.
I'm not comparing it directly. I was just making a comparison to an ICE vehicle which has some % of drivetrain loss. Most people only see the advertised engine HP/Tq #'s by ICE cars and I was just making a comparison to those advertised engine #'s. That's all.
AlanSubie4Life
Efficiency Obsessed Member
We don't know what the drivetrain losses are, nor do we know the conversion efficiency of the battery power to motive power at the motor outputs, so there's no easy way to determine this data at the "crank," unless Tesla tells us (what the source of the 450HP/472lb-ft numbers quoted on initial Performance release were from, I do not know - but that's the only benchmark published "crank" number I have seen). We can only establish a lower limit on the result based on the acceleration data and the reduction ratio (which is close to but not exactly 9:1 from what I understand). And Tesla does not talk about these HP/torque numbers - they prefer to provide 0-60 times (which seems more relevant anyway, and is advantageous (more fair - notwithstanding their inconsistent treatment of Performance and AWD 0-60 times...) to them since they do have lower drivetrain losses than all ICE vehicles).
The minimum net torque value including both motor outputs, assuming 9:1 reduction, after the first 5% boost (assuming no drivetrain losses) is about:
0.86*9.81m/s^2*4250lbs * 13.23in /9 = 448ft-lbs
0.86*9.81m/s^2 * 4250lb * 13.23in/9 in lb-ft - Wolfram|Alpha
The 0.86g is the measured acceleration using a VBOX, for a Performance Model 3 with 20-inch wheels, after the first "5%" power (and torque) boost.
So assuming 5-10% losses, 472lb-ft to 498lb-ft of torque.
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You probably know more about this than I do Alan but my understanding is that with simple direct drive and no drive shaft, the parasitic losses are dramatically reduced. My understanding is that the drive shaft with its awkward 90-degree torque angle translation is particularly parasitic. The system on the Tesla is straight parallel axes torque translation with about a 9 to 1 simple reduction gear to the drive shaft. My guess is it's a 2% to 4% loss if that.
AlanSubie4Life
Efficiency Obsessed Member
Actually no idea, but if that 472lb-ft number pre-5% is correct at all, that would imply about 10% drivetrain losses (assuming about 0.82g of acceleration before that update which I think is what it was). Which, yes, seems high to me.
Unless I am missing a factor somewhere. There is the rotational inertia of the wheels which I am not accounting for in above calculations, so that would mean it's definitely less than 10%. The car as tested could have been 50 pounds heavier than I think...which would be another 1%. The acceleration might have been 0.83g rather than 0.82g...another 1%. Etc. It is conceivable it could be as little as 5% losses.
An acquaintance from my hometown of Portland, OR shared this dyno plot of his Performance Model 3 with overlays from before and after the first 5% power bump back in March. If I remember correctly, it was ~8% boost for AWD LR versions and ~3% boost for the P3D, and it only happened above 45mph.
Here's the original post I made on it from another thread.
I'm reasonably certain the P3D has always been battery limited to a 5C discharge rate (via software).
The P3D peak battery power output was originally 370kW, which at the time was a 5C discharge rate (74kWh useable pack energy). Tesla then unlocked more useable battery for everyone to roughly 78kWh, which is what boosted the original LR RWD range from 310miles to 325 miles and also gave everyone the well-known 5% power boost. This meant the same 5C discharge rate was now 390kW in the P3D, which is exactly what it is right now.
Assuming another 5% power boost, that puts it at ~410kW. This is backed up by data that can be accessed through the vehicle's CANbus, like what MPP does with their motec system and Bjorn Nyland has done in his recent videos showing tons of data from the car's API, including the ~390kW peak power output.
The P3D peak battery power output was originally 370kW, which at the time was a 5C discharge rate (74kWh useable pack energy). Tesla then unlocked more useable battery for everyone to roughly 78kWh, which is what boosted the original LR RWD range from 310miles to 325 miles and also gave everyone the well-known 5% power boost. This meant the same 5C discharge rate was now 390kW in the P3D, which is exactly what it is right now.
Assuming another 5% power boost, that puts it at ~410kW. This is backed up by data that can be accessed through the vehicle's CANbus, like what MPP does with their motec system and Bjorn Nyland has done in his recent videos showing tons of data from the car's API, including the ~390kW peak power output.
AlanSubie4Life
Efficiency Obsessed Member
Really is not consistent with the torque data (in the acceleration plot) in that same thread, which is also posted above in this thread again as well (see link below)...I feel like we had this conversation back in April though.
Not sure I understand why the dyno doesn't show it. But...I know for sure from my data (from VBOX) as well that the acceleration is there all the way up to 40/45mph.
Sleeper Service Accelerometer data
The dyno doesn't show the blue torque curve (the pre +5% reading) that's why the graph is a little misleading.
AlanSubie4Life
Efficiency Obsessed Member
Yeah, but the HP line should have a higher slope as well, below 5k RPM, since HP = Torque *RPM, and we know Torque increased (slope of HP curve = Torque...). But the HP curves only deviate at higher RPM which does not make sense.
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MichaelP90DL
Active Member
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