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[updated with *] P85D 691HP should have an asterisk * next to it.. "Up to 691HP"
- Thread starter krisg81
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- Driving Dynamics Model S
I'm not sure exactly what the chart was requested for, but if it is supposed to be comparing a P85 to a P85D like the chosen numbers suggest, it is missing a key point. The P85 goes from torque limited to power limited at around 45 mph, as you noted in describing the chart. However, because of the higher torque limit from adding the front motor, the P85D goes power limited at 30 mph or so, despite having a higher power limit. Thus, you should see a much higher slope at the front of the graph before settling to something similar.The graph as shown looks to me to approximate what works happen if a P85 somehow acquired 691 horsepower from the rear motor (and thus had Hellcat type traction problems.)Walter
I don't understand the complaints. I pass any car I want with impunity and I have a lowly P85.
Gizmotoy
Active Member
Right. The 30-50 and 50-70 times are extremely good across the model line, and especially so in the Ps. You'll be hard-pressed to find a similar car with better overtake times, and I'm not even sure you can find one that can do it without downshifting.
On the other hand, if your overtakes are 70-90, maybe that's not so great.
mnx
2018 M3P
I was watching a LaFerrari video last week and it's 30-50 time was 1.5s. Apparently the 30-50 time for the P85 is 1.8s... Wonder what it is for the P85D???
I test drove a P85D earlier this year at the store and hit well over 80mph. Did they recently start limiting test drive cars??
OK, you like numbers. So do I. Here's a correction for you: the 350hp figure you calculated is correct as an average. It is actually completely useless though in the case of determining peak hp required for a car.
Instantaneous power can be calculated like this: P=E/t=f*d/t=f*v=m*a*v. Where v is current speed (m/s).
As you can see, the above formula means that if you hold mass and acceleration constant, power rises linearly with speed (which is basically what you see on the power meter on the dash board). Or put it another way: if you double your speed, you'll get half the acceleration (holding power constant). This has nothing to do with gearing or loses.
Assuming constant acceleration: a=v/t=26.822/3.1=8.6522m/s/s (~0.882g)
Right at 60mph, it takes the following power to accelerate at 0.822g (aka the avg rate):
P=E/t=f*d/t=m*a*v=2238.92(kg)*8.6522(m/s/s)*26.822(m/s)=519,586W=693whp.
This does not mean that you need 693whp to get to 60mph in 3.1s. It only means that accelerating at ~0.882g while going 60mph requires this power output.
For example: to get an average of 0.882g, you could accelerate at 1.1g for 1.55s and at 0.664g for the next 1.55s. This would only require a peak power of 520whp (390kW) @ 60mph. Note that due to tire grip limits + electronics current limits and transient response, you really can't accelerate at more than ~1.3g(max) regardless of power available.
Here is a nice graph from DragTimes that demonstrates this acceleration profile. You can calculate peak whp using m*a*v from that graph if you want, but the numbers are a bit off.
Theoretical limit if you had 600whp (450kW @ wheels) available (691 with 13% loss):
(mass w/ driver ~2300kg)
Phase 1: grip+inverter limited
P=m*a*v -> v=P/(m*a) = 450kW/(2300*1.1g*9.81) =18.131m/s =>40.5mph (in 1.68s)
Therefore, from 0-41 power increases linearly (assuming 1.1g acceleration) until it reaches 450kW.
After this speed, power stays constant and acceleration decreases.
Phase 2: Power limited
P=m*a*v -> a=P/(m*v) = 450kW/(2300*60mph*1.61/3.6) =7.29m/s/s =0.74g
So from 40.5mph to 60mph (avg acceleration is 1.1g+0.74g -> 0.92g avg) it takes 0.964s.
Total 0-60 time: 1.68+0.964 = 2.64s. This is pretty close to the ~2.8s number that elon mentioned!!!
(mass w/ driver ~2300kg)
Phase 1: grip+inverter limited
P=m*a*v -> v=P/(m*a) = 450kW/(2300*1.1g*9.81) =18.131m/s =>40.5mph (in 1.68s)
Therefore, from 0-41 power increases linearly (assuming 1.1g acceleration) until it reaches 450kW.
After this speed, power stays constant and acceleration decreases.
Phase 2: Power limited
P=m*a*v -> a=P/(m*v) = 450kW/(2300*60mph*1.61/3.6) =7.29m/s/s =0.74g
So from 40.5mph to 60mph (avg acceleration is 1.1g+0.74g -> 0.92g avg) it takes 0.964s.
Total 0-60 time: 1.68+0.964 = 2.64s. This is pretty close to the ~2.8s number that elon mentioned!!!
No it's not, it just means as your approach 0 velocity your torque approaches infinity and as you approach 60 your torque approaches zero, which means your acceleration force at 60 is also 0, not 0.882g. Of course infinite torque is impossible so no car will ever achieve that, and no one wants to stop accelerating at 60. But an electric motor can get close. AC induction motors are also known for super high torque (and therefore super high current draw) when held stationary, which is why many come with start capacitors.
I just got done testing the new update w/ the 155mph limiter removed. Things I noticed:
1) Speedometer goes up to 160MPH now, all numbers on speedometer and inverter are smaller now.
2) kW gauge pretty much goes to the same area, slightly under 480kW
3) Power does feel better on launch, not a huge difference though. Best launches are still performed using Slip Start, in my opinion.
4) Stabbing accelerator from a roll now feels like it has more 'kick' to it, similar to my old P85. From what I could previously tell, it seemed both front/rear motors were not in sync, one would kick in before the other and there was a slight delay with instant power response. Now, it seems both motors are in sync and have a stronger acceleration effect.
5) Slacker issue I had with music pausing/freezing console when going to next track is resolved
6) Homelink garage door opener had a slight delay when opening/closing garage after I pressed the button- thats gone now.
7) Still no ventilated seats, blind spot awareness is useless, and no CarPlay integration so the car will read and compose text messages. Plenty of room left for Elon to upgrade throughout the year and make our current cars feel outdated
1) Speedometer goes up to 160MPH now, all numbers on speedometer and inverter are smaller now.
2) kW gauge pretty much goes to the same area, slightly under 480kW
3) Power does feel better on launch, not a huge difference though. Best launches are still performed using Slip Start, in my opinion.
4) Stabbing accelerator from a roll now feels like it has more 'kick' to it, similar to my old P85. From what I could previously tell, it seemed both front/rear motors were not in sync, one would kick in before the other and there was a slight delay with instant power response. Now, it seems both motors are in sync and have a stronger acceleration effect.
5) Slacker issue I had with music pausing/freezing console when going to next track is resolved
6) Homelink garage door opener had a slight delay when opening/closing garage after I pressed the button- thats gone now.
7) Still no ventilated seats, blind spot awareness is useless, and no CarPlay integration so the car will read and compose text messages. Plenty of room left for Elon to upgrade throughout the year and make our current cars feel outdated
As a firmware engineer, I can assure you that adding ventilated seats via OTA is difficult. Maybe if the dome LEDs are secretly lasers?
thegruf
Active Member
interesting the S85D display has now been demonstrated to show 315KW=422hp = nominal power.
The P85D, supposedly 515KW = 691hp never appears to show much above ~400KW = well short of nominal and according to kris above this update doesnt improve the max power displayed.
Either Tesla overstated the P85D, or there is a lot more to come with that car.
If I knew the full 515KW was to be unleashed I would buy P85D, as it is i'll probably go for the S85D, then be pissed when the full power is released although I will be 20K bettter off, but still pissed.
The P85D, supposedly 515KW = 691hp never appears to show much above ~400KW = well short of nominal and according to kris above this update doesnt improve the max power displayed.
Either Tesla overstated the P85D, or there is a lot more to come with that car.
If I knew the full 515KW was to be unleashed I would buy P85D, as it is i'll probably go for the S85D, then be pissed when the full power is released although I will be 20K bettter off, but still pissed.
Yep, it does seem that the P85D is turning out to be overrated, as far as the 691 horsepower are concerned. I know there's a lot of mathematician's in here with calculations and other people with various opinions, but the fact still stands- the 416HP P85 ran a best of 111MPH trap speed in the quarter mile (Coincidentally, 111MPH was the fastest trap speed I ran at the drag strip this past weekend w/ my P85D) and the P85D record is 116MPH. How Tesla can get away with advertising the P85D that has supposedly 275 more horsepower than the P85, with only a 5MPH trap speed, is beyond me. I still think the biggest difference in performance between the P85 and P85D is just the added traction of AWD and a little more power from the front motor. Once the enhanced traction advantage is performed (Launch) everything else is very similar across the fleet.
Add the fact the 85D just gained a Sport mode and is now much faster, I would have probably just gone for the 85D instead. The premium I paid for just to have slightly better acceleration at a stop, but zero passing performance advantage over a 85D, is way too much. The 85D is probably the best bang for the buck now, in my opinion.
thegruf
Active Member
@kris, you say you were at the strip at the weekend.
Did you gain any more info re power vs SoC per your opening post that kicked off this rather excellent thread?
Did you gain any more info re power vs SoC per your opening post that kicked off this rather excellent thread?
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Not really, unfortunately. I didn't get a chance to charge to 100% to get a full power run, as I didn't realize it takes so long to Supercharge from 75% - 100%. It was going to take 40+ mins to go from 75%-100%, which is crazy. I emailed Tesla and they replied and said thats normal as the cells need to be topped off. Anyway, I was already running late, so I charged enough so my first pass was at 80%. I got 3 passes in.. the three passes were at 80%, 76%, and 74%. Each run was slower by about .3 - .5MPH in the traps and same with the E/Ts. Just not enough variance in SOC's to have a definitive amount of data. It was way too busy and a bit too hot to stay there with the wife and kids any longer to get more runs in. I'll try again soon!
My best run at 80% SOC was 11.87 @ 111.08 MPH
My worst run was 74% SOC at 11.98 @ 110.76 MPH
My best run with my old P85 was 12.5 @ 109.5MPH (90% SOC)
Unbelievable there is 275 more HP (advertised) vs my old P85, yet the trap speeds are so close together.
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