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Stop the Press! Tesla announces REAL HP numbers for P85D and P90L
- Thread starter Matias
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- Driving Dynamics Model S
Andyw2100
Well-Known Member
Again, this is changing the discussion from the one we were having.
My comment was directed towards Krugerrand responding to Sorka. Sorka brought up the FTC "Truth in Advertising", and Krugerrand responded, talking about people who bought specifically on the power issue. (See below.) My point was that there were those that did not purchase specifically on the power issue. "Expected" and "thought" refer back to Sorka's comment. We were talking about people for whom the truth in advertising law would be applicable. Krugerrand's point was that people for whom motor power was the determining factor should have done more research. Mine was that not everyone affected bought mainly because of the motor power.
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Responding to vgrinshpun here:
The intended meaning of the joke was that you bring up ECE R85 quite a bit. That's all. I don't think you would disagree with that.
I really, honestly did not believe anyone could take the comment literally, in light of how obvious an exaggeration it was, and in light of the smiley face.
stopcrazypp
Well-Known Member
This reminds me of the power vs torque arguments that frequently come up in other auto forums. And that usually refers to peak torque and peak horsepower.
For an ICE car, the conclusions tend to be that peak torque determines low end acceleration and peak power high end (staying in your "power band" at higher rpms).
However, that may be a common misconception of what actually matters in acceleration: wheel torque. The phenomenon that shifting at peak power (which usually is near redline for an ICE) gives better acceleration is not because power determines acceleration, but rather because the wheel torque is significantly higher near redline than next gear up (for an ICE, this is not typically true for an EV which is why multi-speed transmissions make far less sense for EVs). The following article gives a very good explanation of the importance of wheel torque:
http://www.allpar.com/eek/hp-vs-torque.html
That goes to your statement that "the power put down under a curve, not torque, from one speed to another does exactly defines how fast a car accelerates from one speed to another". I don't think that is true.
From your own graphs, acceleration (measured with G) tracks exactly proportional to torque. It does not track proportional to power.
For example, the peak acceleration in that graph (~1.05G) occurred at ~15-20mph and horsepower was only ~300 hp. When the horsepower reached its plateau at ~480-490hp at ~45mph (you pointed out the rest was noise elsewhere), the acceleration had already dropped down to ~0.7G and continues dropping even when horsepower stayed the same.
In general physics (ignoring resistance):
Acceleration=Force/Mass, and the "Force" is wheel torque in this case, not horsepower (that would be Power which is the dot product of Force and Velocity).
Air and rolling resistance varying with speed will also play into this.
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jpet
Jan P.
That makes at least 2 of us. Too bad I can't prove it because it might help some people here seeing our side of the story.
Should we start recording each conversation with Tesla sales advisors going forward? :scared:
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I wonder if any Tesla Sales Advisor received info on the meaning of the term "Motor Power" so that they could subsequently use this knowledge to educate prospective buyers...
Canuck
Well-Known Member
I highly doubt the FTC will take any action against Tesla so I fail to see how this can support your position. If anything, it supports Tesla's position.
stopcrazypp
Well-Known Member
I believe the FTC has two mechanisms for taking action. They can take action by themselves (which seems unlikely to happen in this case), but they can also take action in response to consumer complaints. The latter can still happen.
Canuck
Well-Known Member
I find it highly unlikely that the FTC will see this as anything other than a civil matter between the consumer and Tesla, especially given all the lies that pass as advertising. It seems you need something pretty blatant to get the FTC involved and even then they don't do much. Have you seen all the "gas saver" gadget ads?
I agree.
Truth In Advertising | Federal Trade Commission
Tesla's legal team has no doubt looked at this backwards, forwards and sideways.
As Krugerrand already pointed out, there are a lot of technical specifications that are mentioned in the advertisement of various products.
If the consumer does not understand what those mean, well then he has a responsibility to ask what they mean. If you didn't know what "horsepower motor power" meant, well then it was your responsibility to find out.
If the consumer "assumes" that they mean one thing, and it turns out that they mean another, well then I seriously doubt that is going to go on the manufacturer, especially if the manufacturer is using an accepted standard or using an accepted specification.
The only leg to stand on here, is if it can be proven that Tesla's representatives misrepresented the car as having 691hp.
But since the car is ordered online, and with documentation of it's specifications right there, unless one can clearly demonstrate that they were in fact told such by an agent of Tesla, well then they may not have a case either.
I can file suit right now saying that a Chevrolet salesman told me that the Z06 had 750 horsepower. But I'd need to be able to prove that I was told that.
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Tesla have been misrepreseted in the press earlyer, strangely they handeled this very different than a mirepresentation that could fool costomers to buy the P85D under false premises..
A Most Peculiar Test Drive | Tesla Motors
Tesla vs. The New York Times in a Model S Showdown
Tesla vs. Top Gear | Tesla Motors Norge
Tesla vs. TopGear: Only Half Of The Story
Canuck
Well-Known Member
Because of the parol evidence rule, it's often difficult to get the court to accept into evidence what is said orally when there is a written contract.
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What if the person who said it, admits that they said it?
Wow. Just flat out busted.
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jpet
Jan P.
I'm sure they only said it because they did not know any better and interpreted the available data the same way as the prospective buyers did.
Even Elon said it during interviews, forgetting to add the "motor power" part.
"Tesla sales reps should be doing their research before describing features to potential customers. This is the reps fault for ... Oh wait."
The link you gave me explains that in no uncertain terms.
Thanks.
It seems to say that it's hard to defeat what's "written" using what was "said".
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Where?
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jpet
Jan P.
Indeed, confusing situation, isn't it.
When I bought the car, just after the launch event, no service center in Europe had received any P85Ds to test. The first test drives only became available at around the time the first customers received their P85Ds (5 months after ordering the car). How could the sales advisors have known that "motor power" was not the horse power produced by the motors when driving the actual car? If they had known, I'm sure they would have explained this to prospective customers. I have had enough conversations with them to know that these people try their best to explain things as good as possible. They don't need to misrepresent the performance or anything else about the car. The car sells itself. But Tesla HQ has a responsibility when they put figures on their website. They need to be clear on what they mean, especially if those figures do not represent what the average Joe would expect. I can sympathize with the sales advisors but I can't with Tesla HQ on this matter. Tesla HQ has yet to respond to Andy's letter. Why?
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Indeed, confusing situation, isn't it.
When I bought the car, just after the launch event, no service center in Europe had received any P85Ds to test. The first test drives only became available at around the time the first customers received their P85Ds (5 months after ordering the car). How could the sales advisors have known that "motor power" was not the horse power produced by the motors when driving the actual car? If they had known, I'm sure they would have explained this to prospective customers. I have had enough conversations with them to know that these people try their best to explain things as good as possible. They don't need to misrepresent the performance or anything else about the car. The car sells itself. But Tesla HQ has a responsibility when they put figures on their website. They need to be clear on what they mean, especially if those figures do not represent what the average Joe would expect. I can sympathize with the sales advisors but I can't with Tesla HQ on this matter. Tesla HQ has yet to respond to Andy's letter. Why?
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I didn't look at it all, but that "parole evidence rule" is going to be tough to beat, no matter what he said.
But just for curiosity's sake, can you point me to the spot in the video where Musk says that it has 691 horsepower?
At about 7:58 is the second mention that I hear of 691 horsepower, and Musk himself doesn't say that. The journalist did. But admittedly I didn't watch the whole thing so again, I'd ask where in the video did Musk say "691 horsepower"?
Also, if you're buying speakers, and there are specifications about those speakers that you are unfamiliar with, how is it the manufacturer's responsibility to school you on speakers?
Same with televisions, cameras, and a long list of other items.
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jpet
Jan P.
He confirms the 691 horsepower at 2 minutes into the video. And he adds that the car can do 0 to 100 kms in 3.1 seconds!
Both are not technically correct and they are exactly the things we have been debating about in these threads.
stopcrazypp
Well-Known Member
He doesn't say directly anything about horsepower, but around 2 minutes the interviewer asks "691 horsepower?" and he says "uh yeah".
It seems people on one side expects him to correct the interviewer and say "actually, 691 horsepower motor power". However, I don't think that is a reasonable expectation, as the interview was about his accomplishments and going into a tangent about the intricacies of power rating standards is not something that is fit for the interview (even if Elon is the type to make such corrections).
As I put in another post, in colloquial conversation, when describing the power of the P85D before the new number came out, I will just say "691 horsepower" and not append "motor power" to it as that is unnatural. People who want the details can go to the website. Now that there are two numbers, the situation is a bit different (there can be confusion as to which number) and I'll probably default to the 463 hp number. Personally, I treat "motor power" as just another standard (like how GM specifies "SAE certified" in their website) and it is completely unnecessary and awkward to mention it in normal conversation (I have never heard anyone say "SAE certified" in spoken conversation). It is not "wrong" to not mention it.
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I have no idea what the Black Series driver did or did not do, and neither do you or anybody who is posting here. That is the reason that the speculation on the intent is a footnote to this argument, nothing more. I have no idea why you are choosing to argue based on a footnote.
The fact is that in this video (which, BTW, is not a continuous video, but an edited sequence of cut pieces) the car that the manufacturer rate 0.3s faster is shown driving slower. This means that the Black Series had ¼ mile time at least 0.3s more than tested 11.2s. These are the only two conclusions that can be drawn from this edited video.
So the 1/4 mile time of the SLS electric falls somewhere between the P85D Insane and P90D Ludicrous.
And this is impossible, if one takes your advice of comparing horsepower (and let’s not do a switch here, what you were talking about uptrend and in the (unhappy owners) Letter was hp *rating* provided by the manufacturer, not an *instantaneous* hp at a point on the curve) and uses it as you suggest. The 263lbs lighter car that has between 218 and 287hp less (750-532=218; 750-463=287)can’t have the same ¼ mile time as heavier car with less hp.
So than it follows that SLS Electric 750hp worth of motors are limited by the battery output, conservatively at least to 532hp (similar to Ludicrous) or less. This is the reason MB states that the battery has electric load **potential** of 600kW (805hp). They do so because it is a fraction of a second rating, and battery can’t produce it unless immediately before the test surge it was *not* loaded and its temperature was *not* elevated. This is why their battery can’t provide this power at some point during the acceleration when the motors hit the maximum power point on the curve.
Mercedes SLS electric was not my key lynch pin argument. I was not even the one who brought it up in this conversation – I think it was Darthy001, if I recall correctly – to make the point that listing combined hp rating of the motors *and* the rating of the battery is very simple, in spite of what JB Straubel was saying in his Blog post. Well, it turns out that everybody can be an arm-chair engineer coming with wonderful ideas, but they don’t quite work in real life.
My point was never that it was OK for Tesla to do what they did because Mercedes did the same. You are flat out misrepresenting what all of my posts were about. My point was that Tesla did not use “made-up” hp, aka “fake”’ hp, did not lie, and did not short-change the owners who “did not get what they paid for”. It advertised a car with 691 motor hp, and sold exactly what it advertised, i.e. car with 691 motor hp, capable to go 0 to 60mph in 3.1s. And the motor hp that they advertised was *exactly* the spec that allowed it to beat the predecessor – P85 – by 0.8s in 0 to 60mph.
I was also the one who analyzed ECE R85 and laid out clearly that according to this standard an EV is rated based on motor hp, without taking battery limitation into consideration. All of the people on your side of the argument, including you, disputed this relentlessly and in the face of facts, with great majority without even taking time to read all applicable sections of the standard.
Then, when it became obvious that Tesla indeed rated P85D according to the ECE R85, it over a sudden became irrelevant. If it is irrelevant, why so many on your side of the discussion used words “made-up” “fake” “missing” hp, if not to inflame a discussion, and ignite the indignation with the horrible things done by Tesla.
Well if the fact that hp was “fake”,“made up” was relevant then, than the fact that it was a legitimate rating according to the international standard, used by other manufacturers and the car registration authorities all over Europe is also relevant now. You guys can’t have it both ways.
Well that was my point all along, i.e. that while for an ICEs, which have similar torque/power curves the (max) horsepower per pound metrics *is* a valid way to compare different cars, it is not valid between the ICE and an EV, and not even valid between different EVs. For an EV to ICE comparison, or and EV to EV comparison one needs to look at torque/power curves.
Before further expanding on above, the "hp per lb" of weight that you used uptrend (including your calcs), and the one used in the (unhappy owners) Letter were most definitely based on maximum hp rating (i.e. one number published by the manufacturers), not the power under the curve that you now switched to.
As far as physics fundamentals are concerned, as already noted by Stopcrazypp, the acceleration is defined by applied force (second Law of Newton). As applied to the rotational motion, the acceleration is defined by the applied torque. The acceleration time proportional to total connected inertia and reciprocal to the accelerating torque (the difference between the torque of the motor and load torque).
The reason that peak power per pound is a valid metric to use for comparison of ICE cars is that all of them have similar torque/power curves and all of them are using transmissions to move to the lowest possible gear to maximize torque. In order to minimize acceleration time it is necessary to be on the the portion of the curve with the maximum torque, in the lowest gear, subject to the limit imposed by the maximum hp rating of the engine. So as accelerating car passes beyond point of this max hp, it is necessary to upshift. Upshifting, of course reduces torque due to lower gear ratio, and reduces rate of acceleration.
In the similar fashion, when the car travels at 70mph in the top gear, the torque at the wheel is relatively low because the gear ratio is tall. Downshifting reduces gear ratio and increases the torque at the wheel, but because the engine speed increase, at certain point, as car accelerates, the required power that is proportional to torque and engine speed exceeds the maximum rating, and the transmission need to be upshifted. The power and torque curves of BMW M5 are included below as an illustration.
So the just of all of the above is that both the similarity of the torque/power curves of ICEs and similarity of the method ICE cars are using to maximize the torque at the wheels (transmission shifting) lead to the fact that peak power per pound of weight of the car is a good metric to evaluate how cars accelerate at higher speeds.
The EVs, however, do not have transmissions and have markedly different torque/power characteristics, and comparison between an ICE car and EV using the “hp per lb” becomes meaningless.
Based on the description of the torque/power curve for Tesla EV included in this post, the torque at higher motor speed depends not only on motor maximum hp rating (and by extension, its maximum torque rating), but also on what speed this max power is reached at.
The sooner the maximum power is reached (in terms of motor speed), the more an EV is tuned to a higher acceleration at low speeds but lower rate of acceleration at high speeds. For another EV with the same weight and maximum hp rating, if this rating is reached at a higher speed, the car will accelerate slower at the low speeds and faster than the first car at the high speeds. The “hp per lb” metric based on maximum hp rating no longer uniquely identifies acceleration at the higher speeds. In fact, there is a trade off between how aggressively car can accelerate from a stand still and how good acceleration at higher speeds is.
The above becomes vividly evident by graphing torque/power curves for different EVs, and one of these days, when I have more time, I am going to provide them (yes, I am painfully aware that it is not the first time I share my intent to do this)
So, in conclusion, the metric that is used to compare ICEs, and the one that you advised Andy to include in the Letter is meaningless for EVs.
As was mentioned in JB Blog, the only true metrics that uniquely define performance of the car are 0 to 60, 1/4 mile, etc, acceleration times.
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jpet
Jan P.
Indeed, and I don't want to hold this against Elon. It would be ludicrous :wink: to think he was deliberately lying or anything like that.
The only thing this example helps supporting is that when some of us expected to receive a 691 horsepower car, we had very good reasons to believe this was exactly what we were going to get.
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