Stop the Press! Tesla announces REAL HP numbers for P85D and P90L

[sandpiper]

What? The horsepower that is output at the shaft, which is limited by the battery, wires, fuses, etc is the mathematical definition of the power output by the motor. It is a Newtonian measure of work generated. Is there some other magical source of power that is pushing the car forward? There is only one source of propulsion in this car. It is beyond axiomatic that the amount of horsepower it ouputs is sufficient to account for the performance characteristics of the car. I'm not sure I can read this thread any more today without stabbing a sharp object in my eye.

All true, excepting that at very low speeds your limitation is the current that the motor can handle. Taken to the extreme, at zero speed and full battery current you're producing zero HP but lots of torque (and lots of heat). The larger motor can handle more current at low speed and so at zero speed you have more torque. The HP limitation only comes into play once max motor torque x RPM exceeds available battery power output.

 

[mkspeedr]

If the P85D actually put out 691hp - what would you expect the 0-60 to be?

Personally, I didn't understand why it was only 3.2 at the press launch. I thought it should be around 2.7 (but I still bought one).

 

[vgrinshpun]

I find arguing with people about the technical details tiresome and I usually avoid commenting, but I can't ignore this twice. As I understand it, your position is that because the motor is rated for more horsepower that it produces more torque?

Expressed a different way, are you claiming that the motor produces the same torque when drawing 345,398 watts of power at 9,000 rpm as it would when drawing 515,486 watts? If they decided that they have been too conservative on their estimation of the motor's heat tolerance and up the rating to 800 motor hp, will the engine magically begin to produce more torque at 9,000 rpm even as it still only draws 345,398 watts?

If I am given the motor's efficiency at a particular rpm, can I not calculate the torque directly from the input power applied?

The motor, or, to be more precise the drivetrain (drivetrain includes motor and power electronic module - PEM) power characteristic of P85D consists of two straight lines (ignoring the transients and some minor deviations due to characteristics of two motors having slightly different point of transition between the constant torque and constant hp regions).

The first region, from 0 to about 40mph (quoting by memory and don't have time to check right now) is a straight line connecting zero hp at zero mph point to the (about) 40mph and 691hp point. Based on formula Power = Torque x rpm / 5252, the (tangent of the) angle of this portion of the curve with the mph (rpm) axis is obviously proportional to the torque.

The second region - region of constant power - starts at approximately 40 mph and is represented by horizontal line at 691hp.

The above described motor (drivetrain) characteristic does not take limitation of the battery into account. To obtain the overall power vs. speed characteristic of the vehicle one needs to over-impose the characteristic of the battery on top of the motor characteristic. Making simplifications for the clarity, the battery limitation can be roughly represented by the horizontal line at 463hp. (it is actually a curve slanting down with the increase in speed)

The net result is that the battery limitation curve limits hp starting at about 30mph. Below this speed the motor curve is not affected by the battery limitation. So the torque in this region is T=691 x 5252 / rpm - i.e. defined by the motor hp, not the hp associated with the limitation of the battery. So the 0.8s improvement in 0 to 60 acceleration in P85D as compared to P85 is mostly defined by the fact that from zero to about 30 mph P85D has about 50% higher hp and 50% higher torque as compared to the P85.

Put in another words, the power in P85D, up to the limit imposed by the battery, can be ramped up at a much higher rate than in P85, due to the fact that P85D has roughly 50% higher motor power rating than P85. The torque, of course is a direct measure of the rate of such ramp of power. Graphically this is represented by the angle between the power curve and horizontal axis, with tangent of this angle being proportional to the total rated Torque.

 

[tomas]

Thanks vgrinshpun! Obvious evidence of your calcs: the P85D accelerates far faster than the 85D up to 40 mph. If nothing mattered to performance except battery limited HP, then that would not be the case.

 

[darthy001]

If nothing mattered to performance except battery limited HP, then that would not be the case.

1. Has anyone ever claimed such a case to be true?
2. You are leaving out software limits from Tesla on the 85D. We dont know if they have limited it or by how much. All we know for a fact is that it was heavily limited by software at launch..... Everything else is pure speculation.

 

[Johan]

You must spread some Reputation around before giving it to vgrinshpun again.

Duh.

Is there anyone who could plausibly argue against this wonderfully laid out analysis?

If it was not the case, as Vladimir points out, that in the lower RPM and speed range motor power does make a difference, then why is it in the 0-40 mph that the P85D so outshines the 85D or P85 for that matter, knowing both cars have the exact same battery with the exact same power delivert limitation???

So coming full circle, the whole issue is a communications problem where Tesla have been unable to inform their customers well enough what was inferred by the hp numbers communicated, and buyers that have been expecting miracles without understanding the underlying physics and engineering constraints.

 

[kennybobby]

i would suggest that your lines of power and torque may be reversed.

The plot would show a horizontal line of torque at 687 ft-lbs from 0 to ~31 mph (~3500 rpm). The hp line would ramp up from 0 up to a peak of 463hp at 30 mph. Above 43 mph the torque and power curves would decline from these peak numbers.

The 691 peak hp motor rating would occur at ~6000 rpm (~51 mph) for the two motors if the unlimited power supply used for determination of the peak were available on the car.

The following graph is from the TM patent for the AWD control system. The values were not intended to show actual motors but representative motor performance.

 

[Jian Yang]

Great explanation. This is exactly what lots of people in this thread do not understand. I do think people should read this first before putting down any more arguments, otherwise it is very tiresome and pointless.

The motor, or, to be more precise the drivetrain (drivetrain includes motor and power electronic module - PEM) power characteristic of P85D consists of two straight lines (ignoring the transients and some minor deviations due to characteristics of two motors having slightly different point of transition between the constant torque and constant hp regions).

The first region, from 0 to about 40mph (quoting by memory and don't have time to check right now) is a straight line connecting zero hp at zero mph point to the (about) 40mph and 691hp point. Based on formula Power = Torque x 5252 x rpm, the (tangent of the) angle of this portion of the curve with the mph (rpm) axis is obviously proportional to the torque.

The second region - region of constant power - starts at approximately 40 mph and is represented by horizontal line at 691hp.

The above described motor (drivetrain) characteristic does not take limitation of the battery into account. To obtain the overall power vs. speed characteristic of the vehicle one needs to over-impose the characteristic of the battery on top of the motor characteristic. Making simplifications for the clarity, the battery limitation can be roughly represented by the horizontal line at 463hp. (it is actually a curve slanting down with the increase in speed)

The net result is that the battery limitation curve limits hp starting at about 30mph. Below this speed the motor curve is not affected by the battery limitation. So the torque in this region is T=691 x 5252 / rpm - i.e. defined by the motor hp, not the hp associated with the limitation of the battery. So the 0.8s improvement in 0 to 60 acceleration in P85D as compared to P85 is mostly defined by the fact that from zero to about 30 mph P85D has about 50% higher hp and 50% higher torque as compared to the P85.

Put in another words, the power in P85D, up to the limit imposed by the battery, can be ramped up at a much higher rate than in P85, due to the fact that P85D has roughly 50% higher motor power rating than P85. The torque, of course is a direct measure of the rate of such ramp of power. Graphically this is represented by the angle between the power curve and horizontal axis, with tangent of this angle being proportional to the total rated Torque.

Nice suggestion. Wondering who will actually make this graph. It'd be much easier for people to understand the concept.

i would suggest that your lines of power and torque may be reversed.

The plot would show a horizontal line of torque at 687 ft-lbs from 0 to ~31 mph (~3500 rpm). The hp line would ramp up from 0 up to a peak of 463hp at 30 mph. Above 43 mph the torque and power curves would decline from these peak numbers.

The 691 peak hp motor rating would occur at ~6000 rpm (~51 mph) for the two motors if the unlimited power supply used for determination of the peak were available on the car.

The following graph is from the TM patent for the AWD control system. The values were not intended to show actual motors but representative motor performance.

 

[sorka]

I'm guessing experience with class action lawsuits

The Mazda RX8 class action settlement was for a buyback for any customer who wanted it. This was for overstating horsepower by 10 hp.

The kinds of $36 payout class action suites your talking about are the ones where there are millions of people where the damage is very tiny but the lawyers still take because the class is so large and there's a lot of money to be made even if the per individual payout is small.

- - - Updated - - -

I'd be curious to see power output of those engines at the crank in the vehicles themselves. If the difference is 33% less than the advertised amount, then we'll talk. I guarantee it isn't that far off, since the SAE gross measurements are supposed to approximate the power output at the flywheel/crank shaft.

I'd be happy if the P85D produced 691 HP anywhere in the power train, but it doesn't. The comparisons to SAE gross are getting old and are irrelevant.

But it's a moot point now. Tesla has provided an apples to apples number now. They've declared actual power at the motor shafts which can be compared to actual power at an ICE motor shaft.

I still think they're now low balling it and stating that power at 30% SOC. If they're not, then the loss from battery to motor shaft output is more than 3.5% which I seriously doubt.

- - - Updated - - -

I'm not really buying your analogy. I don't think anyone was ever confused when Elon said the car has "691hp" that he was referring to motor output (not battery input from a supercharger as in your example).

The motor output was never 691 hp. It's what the motors could output if the car was delivered with a power source that provides the required energy which of course it isn't. I don't think there's any confusion about that at all.

- - - Updated - - -

I'm not an expert on the SAE standards (I'm just learning as I'm going along), but for an example, when Cadillac issued a number for both, it was 365 hp under SAE gross, 235hp under SAE net.
"Cadillac issued both net and gross figures for 1972, which were 365 hp and 535 lb-ft SAE gross, 235 hp and 385 lb-ft SAE net. They quoted the same figures for both 1971 and 1972, in this instance."

And tesla could have issued battery (GROSS) and motor shaft (NET) figures as well. The only one that matters from a consumer being able to compare apples to apples is motor shaft power. It's not as good as wheel power but the industry doesn't quote power like that. They quote it at the motor shaft or flywheel.

- - - Updated - - -

Do you mind sharing your letter? I suggest a group letter be drafted asking for a response.

- - - Updated - - -

Suggest two options for Tesla:

1) Refund $20,000 in cash to those who purchased the P85D over the 85D based on marketing material (and sales positioning.)

2) Buy back car at full retail (but, how would the ~$11K in taxes be dealt with? stipulations on tax rebates?)

So, folks who generally like the car can go with #1 else #2. I do not see how free Luda upgrades addresses this problem.

Thoughts?

In california, a vehicle buyback results in a refund of taxes and VLF.

I don't think a full $20K refund would be in order. After all, the P85D is still faster, some, than an 85D at highway speeds and it's a lot faster off the line.

- - - Updated - - -

You said it your self, most people understand hp as being at the wheels, so that is what Tesla should take into consideration when advertising hp numbers.


Really - reference to 1972 Cadillacs to explain why people should have known that the 691 hp number Tesla used was fantacy numbers ...

While all you 'people should have known' are at it, why don't you propose a mandetory master level education for car buyers All the things we as customers should have known, while everything could have been clear if just Tesla had been forthcoming with all information

But when consumers are shopping and comparing horsepower numbers, manufacturers quote at the crank/motor shaft/flywheel and not wheels which is unfortunate, because without that, I'll bet Tesla is due a discount/handicap for having a more efficient drivetrain from the motor shaft to the wheels than any comparable car especially when you consider inertial losses. Inertial losses won't show up in a static speed dyno pull. i.e. if you switch an ICE flywheel to a lightened one and then re dyno on an eddie current dyno at constant speed, the horsepower will be the same. But an acceleration dyno run will show more power due to less inertial losses from that lighter flywheel. Friction losses change a lot less between static and dynamic pulls. The Tesla has a lot less mass in it's drivetrain compared to an ICE so it *should* show more power in an acceleration run at peak vs an ICE that has the same power at it's peak. i.e. two vehicles being dynoed that have the same engine horsepower will show more power on the car that has less drivetrain mass during an acceleration run eve if they both show exactly the same power on a static run.

- - - Updated - - -

The short answer is that P85D with 463 motor hp will definitely not perform as well as P85D with 691 motor hp (with both variants having max available battery output of 463 hp).

+1 :biggrin:

 

[rns-e]

For every car sold in Europe there is also a Certificate of Conformity which lists motor power ratings per ECE R85 which are measured without considering limitations imposed by the vehicle propulsion battery. It is one of these ratings that Tesla used on their ordering page.

yes, which says:

Max hourly output: 66 kW
Maximum net power: 193 kW (front) 350 kW (back)
Maximum 30 min power: 79 kW (front) 90 kW (rear)

None of which adds up to 515 kW or 700 hp that Tesla advertised - but I guess you have a good explanation for that ???

Actually I do not see either 700 hp or 469 hp (as it is in Europe) in any of those ECE R85 numbers, so where do Tesla come up with these numbers from ???? Anybody ???

I find it inconceivable that Danish authorities can find Tesla at fault for using power ratings that are shown on the Certificate of Conformity of the car.

Lets hope that Tesla will have better advice that what you think is inconceivable - as I said in a earlier post, factually correct data used in a misleading way, does not excuse that you used it in a misleading way

And the number is not shown on Certificate of Conformity - see above

 

[sorka]

It's an interesting situation. The P85D has a vastly different power & torque curve than any ICE vehicle. So comparing the peak power of one to the other really is apples and oranges. Peak HP has, historically, been a useful metric only because ICE engines have fairly similar power curves. It really is a useless number when comparing performance of an EV to an ICE.

This is exactly why the P85D has much better off the line performance than ICE cars with even more peak horsepower. The EV make more power at low RPMs i.e. torque. But once both EV and ICE are at their peak power, like say on the highway, the difference mostly vanishes as the ICE car's multi speed transmission keeps the car ICE's peak power in the middle of the gear shifts. I say almost because the shift points aren't going to be at peak. They're going to be on the right of peak right before the shift occurs and on the left of peak right after the shift occurs, so you have to give the Tesla a slight discount due to the fact the ICE won't AVERAGE it's peak between the shifts, but that discount is worth 10s of hp, not hundreds.

- - - Updated - - -

It's the torque, not hp, that most people love about EVs (not some here obviously). When you punch it at a light and your passenger's head is thrown back against the seat with the EV grin that's where most of the enjoyment comes from. Did people really buy an EV with 1 gear for 80-140mph passing speed?

I agree with this statement when it comes to off the line performance. The P85D would be my top choice in stop light to stop light commuting on expressways but would be far from my top choice in highway cruising.

 

[vgrinshpun]

1. Has anyone ever claimed such a case to be true?
2. You are leaving out software limits from Tesla on the 85D. We dont know if they have limited it or by how much. All we know for a fact is that it was heavily limited by software at launch..... Everything else is pure speculation.

There is no evidence of 85D being currently "limited by software".

What I see is the car that is 218lbs heavier than P85 (4848-4630=218) that also has roughly 10% higher motor hp and torque, having same 0 to 60 acceleration as P85. So 85D is heavier than P85, but have similar acceleration because it has 10% more torque.

85D: 259x2=518 motor hp, 243x2=486lb-ft
P85: 470 motor hp, 443lb-ft

 

[travwill]

I always see the new stats that show same equipment used in 70D and 85D now and the aggregate HP difference due to allowable current that seems to be controlled by software.

I wish they would maybe at a "Sport" or "Performance" driving mode to the 70D so we could decide to take a hit on range if we want with the higher output, and higher performance that is the same as 85D (or bit more since lower weight).

-T

 

[sorka]

So for most/many this is an issue of passing performance - acceleration 40 to -say- 100 is much less than expected, and not significantly different than the 85d?

For most of us in the US, that is our main and primary beef is that highway passing power is not what it should have been for a 691 hp 5000 lb car. It is for a sub 500 hp 5000 lb car but that's not what I purchased.

I love the 0-60 times. I've NEVER had an issue with that even though here the US the P85D was the *ONLY* model s quoted with the 1 ft rollout (without actually saying so) while all the variants were quoted *without* the 1 ft rollout which made the P85D's 0-60 appear to be much better than the 85D's and P85's than it actually is. Still, not my beef. I can see why others might have it, but honestly, the current 0-60 is such a head rush that it's almost still a headache.

- - - Updated - - -

It's the torque, not hp, that most people love about EVs (not some here obviously). When you punch it at a light and your passenger's head is thrown back against the seat with the EV grin that's where most of the enjoyment comes from. Did people really buy an EV with 1 gear for 80-140mph passing speed?

I haven't bought a Tesla (yet), but that's exactly what I'm interested in. The 1 gear aspect makes no difference, the power output is limited by the battery, if Tesla did a version with an 8-speed DSG it wouldn't perform any faster at high speed. This is also why the power number is important. Without there is no indication of the cars performance at speed. Obviously a 4WD EV car such as a MS is great 0-20, so posts a really good 0-60 compared to an ICE car. Thus it's hard to use this as a reference to high-speed performance. For this peak output power is a better indication (although again is open to interpretation without the entire power curve), which is why the number is useful.

Having only just found this thread, I am surprised by the size of the difference, and it is disappointing. However, I've also had a test drive of the car, so I've had a chance to actually try the passing performance and judge it for myself.

Actually, after about a 100 MPH, a second gear would start to make a pretty big difference as back EMF starts to kill the AC induction motor's efficiency.

Tesla picked a really good gear ratio that still provided massive off the line performance and efficient performance up to 100 MPH. After 120 MPH, the efficiency just plummets like a rock. So Autobahn drivers would have benefitted from a second gear. The problem is that would decrease efficiency of the drivetrain in the first gear, so I'd still take a single gear as I don't drive at 100 MPH.

 

[dsm363]

Telsa could simply refund the difference in price between an 85D and P85D and software limit the P85D to match the 85D. That way owners would have the exact car they wished they would have gotten knowing what we know now and it would cost Telsa nothing.

 

[sorka]

For every car sold in Europe there is also a Certificate of Conformity which lists motor power ratings per ECE R85 which are measured without considering limitations imposed by the vehicle propulsion battery. It is one of these ratings that Tesla used on their ordering page. I find it inconceivable that Danish authorities can find Tesla at fault for using power ratings that are shown on the Certificate of Conformity of the car.

I disagree. Show me where they specified R85 near 691 hp or anywhere on the ordering page. Or are you saying it was on the european ordering site but not the US?


- - - Updated - - -

Actually this is inaccurate statement. The P85D has torque curve that is defined by 691 motor hp. The maximum power available from tha battery cuts the top portion of the 691 motor hp curve, imposing 463hp limitation. So the total curve is actually a combination of two curves: "691 motor hp" curve with an over imposed "463hp battery limitation curve". The net result is that 0 to 60 acceleration is mostly defined by the "691 hp motor curve", while high speed performance - by the "463hp battery limitation curve"

I think we can all agree that peak torque is NOT limited by the current battery and that peak hp IS limited by the current battery.

 

[wk057]

Telsa could simply refund the difference in price between an 85D and P85D and software limit the P85D to match the 85D. That way owners would have the exact car they wished they would have gotten knowing what we know now and it would cost Telsa nothing.

Pretty sure the two bold portions of the sentence above (bold by me) aren't compatible.

However, I'd happily accept such a resolution. I also stated elsewhere that Tesla is free to buy back my car for 100% of the purchase price. But, I don't expect either.

 

[vgrinshpun]

yes, which says:

Max hourly output: 66 kW
Maximum net power: 193 kW (front) 350 kW (back)
Maximum 30 min power: 79 kW (front) 90 kW (rear)

None of which adds up to 515 kW or 700 hp that Tesla advertised - but I guess you have a good explanation for that ???

Actually I do not see either 700 hp or 469 hp (as it is in Europe) in any of those ECE R85 numbers, so where do Tesla come up with these numbers from ???? Anybody ???



Lets hope that Tesla will have better advice that what you think is inconceivable - as I said in a earlier post, factually correct data used in a misleading way, does not excuse that you used it in a misleading way

And the number is not shown on Certificate of Conformity - see above

You are quoting numbers from the CoC which are not contemporaneous to the motor hp numbers that you quote from the Tesla website. All of the math actually works.

There was a drivetrain revision by Tesla which resulted in higher motor hp. This was addressed in detail by Stopcrazypp - you can find his post if you wish.

BTW, I see no need to scream - 10 question marks spread over 3 sentences seem to be somewhat excessive.

 

[dsm363]

Pretty sure the two bold portions of the sentence above (bold by me) aren't compatible.

However, I'd happily accept such a resolution. I also stated elsewhere that Tesla is free to buy back my car for 100% of the purchase price. But, I don't expect either.

Pretty sure you knew what I meant. No engineering or hardware costs really other than some lines of code. No hardware updates, no service center costs...etc

 

[darthy001]

Telsa could simply refund the difference in price between an 85D and P85D and software limit the P85D to match the 85D. That way owners would have the exact car they wished they would have gotten knowing what we know now and it would cost Telsa nothing.

Had I gotten the range of a 85D as well I would have taken such an offer in a heartbeat

There is no evidence of 85D being currently "limited by software".

No, and I never said so. But the same argument can be used the other way around. There is no evidence it isnt limited is there? Yet you and others use current performance metrics of the 85D as proof for these statements. I am pointing out that such a comparison is by default flawed since you dont know what limits are forced or not on the 85D by software.

The only actual evidence we do have is that the 85D and the P85D was indeed both limited at launch. So back to my point that all of this is speculation as long as you dont have proof that the 85D isnt limited anymore.

Ref the 85D vs P85 acceleration: how do you know the weight-diff isnt purely offset by the added traction of the front motor? Once again no proof I assume, but mainly speculation sold as "facts"..

All might be correct in these speculations, but you really cant prove it.