This has been argued to death. Some people do. If you don't, that's fine, but we don't need this thread to devolve into back and forth over that point.
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
-
On today's TMC Podcast, we ask the question "What is the Tesla Cybercab?". Join us on YouTube live at 1PM and participate in the chat.
Tesla blog post: AWD Motor Power and Torque Specifications
- Thread starter dsm363
- Start date
-
- Tags
- Driving Dynamics Model S
This has been argued to death. Some people do. If you don't, that's fine, but we don't need this thread to devolve into back and forth over that point.
Pretty much sums it up. When the Model S first came out, Tesla's stated performance AND horspower ratings were conservative. Onece the D cars were introduced(or maybe a bit before), Tesla changed their ratings, and now their ratings are overstated. It's as simple as that. The Blog post explains the difference between ICE cars and EV's, but that's not the real issue. The real issue is Tesla going from overdelivering to underdelivering.....
dhanson865
Well-Known Member
expectations vs reality.
The ability to make informed decisions if you can't afford to buy one of each of
S40
S60
S70
S85
S90
P85
P85+
S70D
S85D
S90D
P85D
P85D + Ludicrous mode
P90D
P90D + Ludicrous mode
If the numbers are realistic you could make an informed decision without buying 14 different Model S configurations to make your own comparison tests. Ideally since Tesla isn't doing it some organization would get all the cars together in a controlled environment with as similar spec tires, SOC, temp, etectera and make a comparison table.
But even if someone did there will be Model X soon and then some other trim/option change next year/and the amount of research will never end.
People are just asking for apples to apples numbers so they can make decisions no matter if they are selling a non Tesla car to buy a Tesla or selling an older Tesla to get a newer Tesla.
Not having the numbers just breeds confusion, resentment, arguments, complaints, etcetera. You might have some of that no matter what you do but consistent accurate data allows forum members to field newbie questions in a constructive matter of fact neutral tone instead of having to add to the thread their own frustration that no one has all the data they want.
All Tesla has to do is get all geeky with one of each model that comes off the line and post test results. They don't even have to post those numbers on the ordering/configuration website. Just share real world data of every major configuration that affects the drive train and we'd at least have data to pour over. Then they could put less info on the configuration pages and send the people that need the numbers into the spreadsheets or PDFs or however they share the data.
Think about it there are 9 or 10 configurations currently available in the online store between Motors, Batteries, and Ludicrous mode and the only clear information is cost. Range and performance vary wildly due to tons of variables. Most of us want more data on both. The HP guys just put a stronger voice behind the request for more data.
Last edited:
In 1972, American manufacturers phased in SAE net horsepower. This is the standard on which current American ratings are based. This rating is measured at the flywheel, on an engine dyno, but the engine is tested with all accessories installed, including a full exhaust system, all pumps, the alternator, the starter, and emissions controls. The standard also accounts for atmospheric correction due to temperature, humidity and barometric pressure.
Prior to this manufacturers measured GROSS horsepower often without using intakes or exhausts with no accessories attached.
It's true that there isn't a standard yet account for the differences in how you measure power from an electric drivetrain, but the P85D only produces 550 hp GROSS at the battery. Any standard you could come up with will only measure less power.
There's only a 52 peak hp difference from the battery between an 85D and a P85D but there *was* a 315 hp difference advertised on Tesla's site before they removed the 691 hp rating. The 85D makes 504 hp for *REAL* while the P85D only makes 555 hp. That difference narrows as both of those models SOC levels go down. So why did they remove the combined hp rating of the P85D and not the 85D or other models???
So now I formally take back what I said in previous posts that Tesla hadn't intentionally mislead us. They are now formally stating in this blog that they their combined power rating was indeed the individual motor ratings of each motor combined and not the true horsepower. This was clearly misleading and not stating the true horsepower like there did for the other Model S variants including the 85D and 70D.
On the plus side, Tesla has formally declared what they intended and there's no reason to debate this any longer. They admit that the P85D doesn't make 691 hp and they now admit how that number was arrived at.
As for their 0-60 explanation, I'm satisfied with that except that the 0-60 times of other Model S variants were specified without the 1 ft rollout. i.e. the P85 does 0-60 in 4 second and the S85 does 0-60 in 5 seconds both with a 1 ft rollout, but their speced times were slower because they weren't using the 1ft rollout for those models.
- - - Updated - - -
It is that useful if you're already at speed and you're using your 8 speed transmission to keep the engine near it's peak during acceleration. It doesn't help as much from a dead stop because you have to get to that peak in the first place which is why electric cars have a big advantage there with the ability to produce maximum torque at 0 RPMS.
- - - Updated - - -
It doesn't accelerate as fast on the freeway as an M5 or RS7 both of of which only have 560 and a power to weight ratio of 1 hp for every 8 lbs . I noticed as I drove it home that it did not accelerate as fast as it should on the freeway if it had really had the claimed hp. I was not able to experience this during the test drive because the test models were speed limited and cut power early. When I mentioned to the sales guy that even from 60 to 80 the P85D didn't feel like it had close to 700 hp for that weight of car, he said it was because it starts cutting power early so that when you hit the 80 MPH speed limiter that it doesn't jar by suddenly cutting acceleration. I believed this and also believed it was a reasonable explanation. Given the car was so fast from 0-60, I didn't have a reason to doubt this.
If you bought a P85D in October 2014 it claimed to have "combined motor power" of 691hp.
If you buy one today the design studio tells you that the rear motor makes 509 and the front motor makes 253. That's 762hp.
But today's car has exactly the same performance characteristics as the one from October 2014.
And the motor power figures for the P90DL are also 509 and 253, despite it having very different performance characteristics.
So it seems that these "motor power" numbers are a completely useless measure of the car's performance, in which case why are they in the design studio at all?
- - - Updated - - -
Also has nobody told JB that the 60 was discontinued quite a while ago, and the entry level RWD model has a 70kWh battery?
If you buy one today the design studio tells you that the rear motor makes 509 and the front motor makes 253. That's 762hp.
But today's car has exactly the same performance characteristics as the one from October 2014.
And the motor power figures for the P90DL are also 509 and 253, despite it having very different performance characteristics.
So it seems that these "motor power" numbers are a completely useless measure of the car's performance, in which case why are they in the design studio at all?
- - - Updated - - -
Also has nobody told JB that the 60 was discontinued quite a while ago, and the entry level RWD model has a 70kWh battery?
Last edited:
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
Yeah - wzup with that? Seems kind of detached from the day-to-day business of Tesla? And like Brianman said: he didn't even mention the number 691 anyore in the blog post!
ERP
Ludicrous Member
This says it all.
So, 85D and 70D = stated motor power
P85D ≠ stated motor power
Of course, taken literally, the last sentence sounds like the two motors are creating more power than the batteries are supplying.
So, 85D and 70D = stated motor power
P85D ≠ stated motor power
Of course, taken literally, the last sentence sounds like the two motors are creating more power than the batteries are supplying.
Last edited:
I do not find an explanation in the blog post, why Tesla changes the kind of acceleration measurement they use. AFAIK most of their models get measured "without rollout" and only the most expensive models get measured "with rollout". And these numbers are presented side by side without a hint that they are measured in completely different ways and are not comparable at all. I my eyes, this alone is still a scam.
And I do not get their explanation for the missing HP either. I mean, what does this mean:
Sounds as if motor shaft power can exceed battery electrical horsepower. Really? Where is the energy coming from? If you can tell me, how to generate energy out of nothing, I will propose you for the next physics nobel prize.
And why don't they show the combined HP for their most expensive D models like they do for the cheaper D models? Again, to me this does look like a scam.
And I do not get their explanation for the missing HP either. I mean, what does this mean:
Sounds as if motor shaft power can exceed battery electrical horsepower. Really? Where is the energy coming from? If you can tell me, how to generate energy out of nothing, I will propose you for the next physics nobel prize.
And why don't they show the combined HP for their most expensive D models like they do for the cheaper D models? Again, to me this does look like a scam.
All in all I would say that prior to this blog article I was basically fine about all this stuff. Yes, they did a silly marketing thing and added two numbers that shouldn't really have been added, but hey all the auto companies do this, and the P85D is a very quick car which at least up to 60mph feels like something with 691hp, which makes the comparison not unreasonable especially since the Model S is not a track car and itsn't likely to spend much time on the wrong side of 100mph.
But this blog article has really pissed me off. It is condescending bullsh1t of the worst kind; it is self-contradictory and muddled; and all it has done is highlight all the ways in which TM's figures were, and still are, inconsistent across their range, with no justification given for why that should be so.
Another home run for the Tesla Communications machine.
But this blog article has really pissed me off. It is condescending bullsh1t of the worst kind; it is self-contradictory and muddled; and all it has done is highlight all the ways in which TM's figures were, and still are, inconsistent across their range, with no justification given for why that should be so.
Another home run for the Tesla Communications machine.
Did anybody here really expect Tesla to come clean and admit they screwed up? They are just digging a deeper hole with that blog post.......
When one gets caught in a lie, they either admit it, or make it worse by making up a ton of BS. Tesla chose the BS route.
When one gets caught in a lie, they either admit it, or make it worse by making up a ton of BS. Tesla chose the BS route.
ERP
Ludicrous Member
I still had it open, so here is a copy.
JB Straubel, Chief Technical Officer September 21, 2015
Attempting to directly correlate horsepower ratings in petroleum burning vehicles to horsepower in an electric vehicle is a difficult challenge. The physics of an electric vehicle propulsion system are very different from a gasoline one. In an EV, electrochemical reactions in the lithium ion cells create electricity. That electricity flows through power electronics that control the voltage and current, then it flows to electromagnets in the motor that create powerful magnetic fields rotating the shaft to turn the wheels. The power required to rotate this shaft has the most correlation to traditional measures of horsepower. However, the chain actually begins in the electrochemical reactions that happen in the battery pack. Depending on the battery's temperature, state of charge and age, the amount of electricity extracted can vary widely.
There is some confusion about our methodology for specifying "equivalent" horsepower ratings for our all-wheel drive, dual motor vehicles – the "D" versions of Model S. This document will hopefully answer those questions.
Electrical "Horsepower"
Defining electric power in terms of horsepower is not very intuitive. Kilowatts or Megawatts are a much more useful unit. Electricity alone can't generate physical motion the way a horse or a fuel-burning engine does. An electric motor converts electricity into motion. Think of electric power as flowing much like fuel flows from a tank to an engine. Various situations (low state of charge, cold temperatures, etc.) can reduce this flow of electrons below the ultimate capability of the electric motor. In other cases, the potential flow of electricity may exceed the capability of the electric motor (warm battery, short duration accelerations, etc.). Since the battery electric horsepower rating varies it is not a precise number to use for specifying the physical capability of an EV. The motor shaft horsepower, when operating alone, is a more consistent rating. In fact, it is only this (single or combined) motor shaft horsepower rating that is legally required to be posted in the European Union.
Dual Motor vs. Single Motor (P85 vs. P85D)
The shaft horsepower rating of the rear wheel drive single motor Model S is straightforward and roughly 360-470 hp depending on the variant (60, 85 or P85). Also, it is generally similar, but not the same, as the battery electrical "horsepower" output. The difference is most obvious to drivers when the battery is at a very low SoC. In this state, the chemical reactions generate less voltage and less equivalent horsepower, even though the physical electric motor hasn't changed. The maximum torque the electric motor(s) are capable of is nearly unchanged as the battery horsepower changes even though the maximum shaft horsepower is reduced as the battery horsepower reduces.
When we launched the all-wheel drive P85D, we took the straightforward and consistent approach of specifying the combined capability of the two electric motors, front + back. The torque from the two motors comes together resulting in a huge boost in acceleration, the "g's" you feel in a P85D. This is why Insane Mode is so delightful. The vehicle takes off slightly faster than 1g of acceleration delivering the amazing 3.1 second 0-60 mph (96.6 kph) performance. This acceleration was verified by Motor Trend using a base vehicle and medium weight driver. It should be noted that a larger occupant and additional options that increase weight will reduce the acceleration. Also, the Motor Trend standard excludes the first 28 cm of rollout. Including this rollout adds approximately 0.2 seconds to the acceleration.
One additional note is that, while gasoline cars get worse with altitude, electric cars actually get faster. All cars experience reduced air resistance, but gasoline cars become increasingly oxygen-deprived the higher they go. The Motor Trend test was done at approximately sea level, so the Model S will outperform a combustion car of the same nominal acceleration as altitude increases.
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.
All Wheel Drive 85D and 70D
Where some confusion occurs is that in the 85D and 70D vehicles the combined motor shaft power is very similar to the battery electrical horsepower under many normal conditions. With the P85D the combined motor shaft power can often exceed the battery electrical horsepower available. The dual motors utilize the battery horsepower in the widest variety of real world conditions. The true measures for any performance EV driver are acceleration times and driving performance of the vehicle.
JB Straubel
Tesla All Wheel Drive (Dual Motor) Power and Torque Specifications
JB Straubel, Chief Technical Officer September 21, 2015
Attempting to directly correlate horsepower ratings in petroleum burning vehicles to horsepower in an electric vehicle is a difficult challenge. The physics of an electric vehicle propulsion system are very different from a gasoline one. In an EV, electrochemical reactions in the lithium ion cells create electricity. That electricity flows through power electronics that control the voltage and current, then it flows to electromagnets in the motor that create powerful magnetic fields rotating the shaft to turn the wheels. The power required to rotate this shaft has the most correlation to traditional measures of horsepower. However, the chain actually begins in the electrochemical reactions that happen in the battery pack. Depending on the battery's temperature, state of charge and age, the amount of electricity extracted can vary widely.
There is some confusion about our methodology for specifying "equivalent" horsepower ratings for our all-wheel drive, dual motor vehicles – the "D" versions of Model S. This document will hopefully answer those questions.
Electrical "Horsepower"
Defining electric power in terms of horsepower is not very intuitive. Kilowatts or Megawatts are a much more useful unit. Electricity alone can't generate physical motion the way a horse or a fuel-burning engine does. An electric motor converts electricity into motion. Think of electric power as flowing much like fuel flows from a tank to an engine. Various situations (low state of charge, cold temperatures, etc.) can reduce this flow of electrons below the ultimate capability of the electric motor. In other cases, the potential flow of electricity may exceed the capability of the electric motor (warm battery, short duration accelerations, etc.). Since the battery electric horsepower rating varies it is not a precise number to use for specifying the physical capability of an EV. The motor shaft horsepower, when operating alone, is a more consistent rating. In fact, it is only this (single or combined) motor shaft horsepower rating that is legally required to be posted in the European Union.
Dual Motor vs. Single Motor (P85 vs. P85D)
The shaft horsepower rating of the rear wheel drive single motor Model S is straightforward and roughly 360-470 hp depending on the variant (60, 85 or P85). Also, it is generally similar, but not the same, as the battery electrical "horsepower" output. The difference is most obvious to drivers when the battery is at a very low SoC. In this state, the chemical reactions generate less voltage and less equivalent horsepower, even though the physical electric motor hasn't changed. The maximum torque the electric motor(s) are capable of is nearly unchanged as the battery horsepower changes even though the maximum shaft horsepower is reduced as the battery horsepower reduces.
When we launched the all-wheel drive P85D, we took the straightforward and consistent approach of specifying the combined capability of the two electric motors, front + back. The torque from the two motors comes together resulting in a huge boost in acceleration, the "g's" you feel in a P85D. This is why Insane Mode is so delightful. The vehicle takes off slightly faster than 1g of acceleration delivering the amazing 3.1 second 0-60 mph (96.6 kph) performance. This acceleration was verified by Motor Trend using a base vehicle and medium weight driver. It should be noted that a larger occupant and additional options that increase weight will reduce the acceleration. Also, the Motor Trend standard excludes the first 28 cm of rollout. Including this rollout adds approximately 0.2 seconds to the acceleration.
One additional note is that, while gasoline cars get worse with altitude, electric cars actually get faster. All cars experience reduced air resistance, but gasoline cars become increasingly oxygen-deprived the higher they go. The Motor Trend test was done at approximately sea level, so the Model S will outperform a combustion car of the same nominal acceleration as altitude increases.
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.
All Wheel Drive 85D and 70D
Where some confusion occurs is that in the 85D and 70D vehicles the combined motor shaft power is very similar to the battery electrical horsepower under many normal conditions. With the P85D the combined motor shaft power can often exceed the battery electrical horsepower available. The dual motors utilize the battery horsepower in the widest variety of real world conditions. The true measures for any performance EV driver are acceleration times and driving performance of the vehicle.
JB Straubel
anticitizen13.7
Not posting at TMC after 9/17/2018
It's still up. I just read the post.
My take on this is that Tesla did screw up, because there was no need to overstate actual peak delivered horsepower from the entire system. 0-60 in 3.1 is already extremely impressive for a large sedan. Why puff things up when it's already great?
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
Still there for me.
After the comments there and JB reading here on TMC I hope and believe that he, or his staff, will decide to change it or come out with an additional clarifying post.
In my opinion, unfortunate as it is, this is a communications failure (again).
After the comments there and JB reading here on TMC I hope and believe that he, or his staff, will decide to change it or come out with an additional clarifying post.
In my opinion, unfortunate as it is, this is a communications failure (again).
Last edited:
While good to find JB is back, I found his essay frustrating. System power is nothing new. It reads like they are asking for slack, on "battery chemical horsepower". The drums of a dyno machine don't care any more about that, than they do fuel. That is why we let them control for representations, that otherwise seem to be getting out of control.
Mod Note: A post (and response) was moved to snippiness. Tensions are high, but let's please try not to lash out at fellow forum members.
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
Edited my post to clarify it was an opinion on my part, not a claim of the blog having been changed or amended. Sorry if I stepped on some toes.
ZachShahan
Active Member
I assume he mentioned 60 kWh because that is what many people have. Or he partially wrote this up a while ago and just came back to it. He mentioned 70D later on.
I think I understand the frustration of some people here, but my more forgiving take on it is:
1) Tesla knows that EVs accelerate faster than ICE vehicles but don't often get credit for it when you simply look at specs (even looking at the 0-60 time doesn't capture how quick a Tesla is off the line). To try to counter that a little for the people who would simply be comparing the numbers while sitting on their couches at home, and because it was technically accurate and there's no real standard for EVs, it used the combined figure.
2) They figured people would buy the cars based on how they drove, not based on some numbers on the website.
3) They used the same system as they had used before, but didn't think (or want) to explain to everyone that the P85D would not be able to use all of its rated horsepower.
4) After people got pissed here, they decided to clarify the matter. However, it would be irresponsible of a company to put its decisions in bad light, so they clarified in a neutral way rather than saying, "we made a big mistake by indicating horsepower for the P85D that it can't use in the real world." If they were only talking to Tesla owners, they'd probably be fine saying this, but they know how the media takes things and they don't want to turn this into a press nightmare... which they've had enough of for illogical reasons.
5) The wanted to use the nice 0-60 time Motor Trend got for the P85D but didn't think to use the same system for the other models. (Of course, if they thought about the fact that the systems are different and overhype the P85D compared to other Model S options, that would be very crappy. I'll give them the benefit of the doubt here, but this is the issue that is most sketchy and most likely to be somewhat deliberate deception in my opinion.)
I imagine these responses won't be popular here, especially with customers who are pissed off their cars aren't more powerful, but I think this is a realistic human take on these decisions.
stopcrazypp
Well-Known Member
That's not the correct interpretation in my opinion. Under GROSS power, the only thing tested that needed to be stock was the engine. The analogy with the P85D is that the motors are the ones under test (not the batteries). Thus the battery limitations being left out would be similar to an engine without the stock exhaust and with an optimal tune (non-stock) as tested under SAE GROSS power. In both cases, if you took a probe to any point in the car in the stock configuration, at no point does it measure the rated GROSS power. All that number represents is the power of the engine with no regard for limitations elsewhere.
And rather than using the gross power analogy, Straubel seems to be saying the European test standard is the same way (the "drivetrain" under test does not include the battery).
I actually can still see the blog post right now.
Similar threads
- Marketplace listing
- Question