I'm not familiar with dyno's but i hope you can get enough traction to get a reading. Don't forget people are slamming their foot down in insane mode and the tesla responds, a traditional ICE that produces max power at 7k RPM works in a Dyno but you need no slip and full current draw very soon to see its true power potential in the tesla. I'd bet thats very hard to do on most dyno's.
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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
It does not reduce power. The KW meter is solid after it reaches 30 MPH and does not let off.
Um, it's physics. At 100% conversion, 1 KW = 1.34102209 hp. 480K is 644 hp at 100% converison. Obviously it's not 100% even at the motorshaft so hp will be even less at 480KW. However, the meter never reaches that. At best, it's reaching 430KW and maybe even only 400KW. Assuming 430KW, the best theoretical hp by the laws of physics, at least in this universe, is 576 hp at 100%. If you factor in inverter losses(7%) and AC induction motor losses(10%), then you're left with 482 hp at the motor shaft. I don't go further down the drivetrain because comparing SAE power is also done at the crankshaft of an ICE.
thegruf
Active Member
gearing (Tesla single speed, Lambo 7?) and considering wheel torque I think solves the confusion, HP is a bit of a nonsense really (especially in the case of EVs) as you have to consider over what rev band that HP is available. Considering area under the torque curve is much more revealing.
fwiw I reckon that Tesla is stating 691KW as the max input power draw to the motors, not a measure of the mechanical output power. (If you think about it, is is rather difficult to rate the input power to an ICE (fuel quality/temp/altitude etc) but very easy to measure input power to an electric motor (multimeter!). Does make comparison even less relevant though.
Danal
electricmotorglider.com
\
Chassis Dynamometer - Dynamometers | Dynapack (International Dynamometers Ltd)
PERFECT!! This is THE ANSWER to all P85D power questions.
Where can we utilize one?
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gvands
Member
Just thinking about the not so impressive overtake capability of the P85D according to alot of posts I read here...
I don't have my Tesla yet, so I can't test, but when it comes to overtaking on the highway, what if you would do the same as an insane launch and
take your foot of the pedal for just a moment and then slam it down? Could this result in faster speeds?
I don't have my Tesla yet, so I can't test, but when it comes to overtaking on the highway, what if you would do the same as an insane launch and
take your foot of the pedal for just a moment and then slam it down? Could this result in faster speeds?
P85D 691HP should have an asterisk * next to it.. "Up to 691HP"
Everything is relative. The P85D has no problem accelerating on the highway to pass. It's that the rate of acceleration at speed (60+) is disproportionately slower than the rate of acceleration at slower speeds. It's really a first world problem. My only problem passing at speed is that I end up in three digit territory :/
Everything is relative. The P85D has no problem accelerating on the highway to pass. It's that the rate of acceleration at speed (60+) is disproportionately slower than the rate of acceleration at slower speeds. It's really a first world problem. My only problem passing at speed is that I end up in three digit territory :/
The power P required to accelerate the car is P = mav, where m is mass of the car, a is the acceleration of the car, and v is the speed, or a = P/(mv). It takes more power to accelerate at the same rate at higher speeds. If it takes P power to accelerate at rate a at 20 mph, then it will takes twice as much power to accelerate at the same rate at 40 mph, and three times as much power at 60 mph.
Can someone render a 691hp-to-wheels curve vs 416hp-to-wheels acceleration curve? Actually I'd like to see 3 charts showing the two curves intercepting at: (1) 0mph, (2) 30mph, and (3) 60mph?
For the shape of the two curves, use whatever you think reasonable. Perhaps the shape shown for the P85 way back when in Tesla's blog?
Thanks.
From the data in post 254, the following plot estimates what speed vs. time would be if the maximum output power of the motor were 691 HP and 416 HP. The blue curve is the actual speed vs. time for the P85D from the spreadsheet data in post 254. The red curve would result if the motors output a maximum power of 691 HP. The green curve is for 416 HP. If maximum power output of the motors were 691 HP, 0 to 60 MPH could be achieved in 2.9 seconds. Below 45 mph, acceleration is limited by the maximum torque of the motor. Above 45 mph, it is limited by maximum power output. So to improve 0 to 60 mph, Telsa needs to output more torque at speeds below 45 mph and/or more power at speeds above 45 mph.
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So add my own data now. On my way to work this morning. Not sure where the change occurred or if it was a taper, but I noticed accelerating at 60% SOC that it noticeably slower than at 80%. The KW meter peaked at the mid point between 240 and 480 rather than partially covering the "0" in the 480 label like it does at a higher SOC.
Is there a way to collect moment by moment KW usage in VT? I left it on and running, but it doesn't log very frequently.
Is there a way to collect moment by moment KW usage in VT? I left it on and running, but it doesn't log very frequently.
<science>
How much power does it take to accelerate a given mass to a given velocity?
P=W/t
W=Fd
F=ma
d=.5at^2
a=v/t
P=W/t=Fd/t=mad/t=(m(v/t)(.5(v/t)t^2)/t=(.5m(v^2/t^2)*t^2)/t=.5mv^2/t
thus:
P=.5mv^2/t where P is watts, m is in kg, v is in m/s, and t is in seconds.
P85D weight 0-60: (.5*2238.93*(26.8224**2))/3.1 = 259,802 Watts.
Of course in HP that's ~350 HP.
Show me a 5000lbs car with 350 HP, electric or ice, that will hit 0-60 in 3.1 seconds... Of course not, getting the nameplate horsepower actually output in a useful way is some ridiculous fantasy.
For those of you about to complain about drag, go ahead do the calculation, you should find it's nearly insignificant compared to the amount of energy used to accelerate the mass when you've only been moving for 3.1 seconds.
Stick that in your pipes and smoke it....
</science>
How much power does it take to accelerate a given mass to a given velocity?
P=W/t
W=Fd
F=ma
d=.5at^2
a=v/t
P=W/t=Fd/t=mad/t=(m(v/t)(.5(v/t)t^2)/t=(.5m(v^2/t^2)*t^2)/t=.5mv^2/t
thus:
P=.5mv^2/t where P is watts, m is in kg, v is in m/s, and t is in seconds.
P85D weight 0-60: (.5*2238.93*(26.8224**2))/3.1 = 259,802 Watts.
Of course in HP that's ~350 HP.
Show me a 5000lbs car with 350 HP, electric or ice, that will hit 0-60 in 3.1 seconds... Of course not, getting the nameplate horsepower actually output in a useful way is some ridiculous fantasy.
For those of you about to complain about drag, go ahead do the calculation, you should find it's nearly insignificant compared to the amount of energy used to accelerate the mass when you've only been moving for 3.1 seconds.
Stick that in your pipes and smoke it....
</science>
Don't even worry one bit. I got scared after reading all these posts and was worried that our P85D will be disappointing once I test it at highway speeds. After delivery, I'm glad to report it isn't disappointing at all. Is it less powerful than its insane 0-60 launch? Yes. Does that make it slow? HECK NO. I'm enjoying this thing to its fullest.
Apologies ahead of time if this has already been covered somewhere in this thread. I'm not sure if it's just because I'm used to car now, but it seems a tad slower than before. Took a video then a snapshot of launches from a standstill, and then also on the highway. In both cases the power hits a wall at the same exact point. Is this what you guys are seeing? Barely scraping the 0 in "480", but certainly a couple ticks from getting there (estimating 390). Am I just used to the speed now? Or is it actually slower....
At max charge, it covers a tiny bit more of the 0, but not much more.
I strongly suspect as well that if you go test drive a P85D at a Tesla Store..you know, one of those ones that has been speed limited to 80, I'll bet you see that needle go past 480. I'll bet the test drive units are setup to be ringers and have full power. We already know it's limited by software.
The problem is, those test driving them before they own them aren't going to remember *exactly* where that needle goes.
I strongly suspect as well that if you go test drive a P85D at a Tesla Store..you know, one of those ones that has been speed limited to 80, I'll bet you see that needle go past 480. I'll bet the test drive units are setup to be ringers and have full power. We already know it's limited by software.
The problem is, those test driving them before they own them aren't going to remember *exactly* where that needle goes.
I highly, highly doubt this. What I don't doubt is that they keep those cars at 90-100% SOC as often as they can for test drives. But I also do not believe they do this to skew the numbers and/or fool people, but merely to have enough electricity to complete multiple test drives back-to-back as the day goes on.
thegruf
Active Member
@Rice390 - havent seen the gauge that closeup before, thanks.
Seems it is indicating more like 320-360KW to me.
Waaay short of 515KW.
Anyone able to challenge Tesla to explain this?
Seems it is indicating more like 320-360KW to me.
Waaay short of 515KW.
Anyone able to challenge Tesla to explain this?
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