Tesla blog post: AWD Motor Power and Torque Specifications

[dsm363]

Tesla All Wheel Drive (Dual Motor) Power and Torque Specifications | Tesla Motors

Tesla finally addressed the issue officially.

 

[sandpiper]

That is a very very well written response. And it probably reflects something close to reality. I'm betting that, internally, Tesla was more concerned about performance, and that in coming up with their marketing specs they fairly simply added up the motor HPs without a lot of consideration for the battery.

Personally, I hope this is start of the end for this issue.

 

[scaesare]

Hmm.

The crux of the article is that Tesla publishes the combined shaft HP numbers the motors are capable of, even though there are factors (pack SOC, temp, traction, front/rear torque-split, etc...) that may at times prevent that combined total from being reached.

However, most HP figures for vehicles are the peak ratings for what the system as a whole is capable of under ideal conditions. Even if an ICE engine itself is capable of 400HP, you can't publish that if the fuel pump is only capable of delivering 350HP worth of fuel rate.

IOW: You need to be able to demonstrate full HP under ideal manufacturer-specified conditions.

Does the P85D ever deliver a measurable 691HP? My understanding was no...

 

[sandpiper]

Hmm.

The crux of the article is that Tesla publishes the combined shaft HP numbers the motors are capable of, even though there are factors (pack SOC, temp, traction, front/rear torque-split, etc...) that may at times prevent that combined total from being reached.

However, most HP figures for vehicles are the peak ratings for what the system as a whole is capable of under ideal conditions. Even if an ICE engine itself is capable of 400HP, you can't publish that if the fuel pump is only capable of delivering 350HP worth of fuel rate.

IOW: You need to be able to demonstrate full HP under ideal manufacturer-specified conditions.

Does the P85D ever deliver a measurable 691HP? My understanding was no...

As I understand it, there are specific SAE standards for reporting HP in ICEVs but there none for EVs yet. It's more than just the engine peak HP. I believe it also includes specific accessories, and assumes some drive train losses. Because EVs are so different, those conditions simply aren't defined at this point. And if the goal is to make EV and ICEV numbers comparable for comparison purposes, then that gets even muddier. I suspect that, once standards are set, that Tesla will have to revise their numbers. But that's a debate for another day.

Anyway... that's as far as I'm going to wade into this debate because it's become somewhat of a religious war. My car does what I expected to and I'm happy!

 

[AnOutsider]

No horse in this race, but that came across as side-stepping the real issues owners are bringing up (some of which are mentioned in the comments)

 

[sandpiper]

No horse in this race, but that came across as side-stepping the real issues owners are bringing up (some of which are mentioned in the comments)

Tesla more or less confirmed, in their blog, that the battery won't deliver enough power to provide the full combined motor HP. The big question is... is it relevant? Tesla is saying no, it's not in any practical way. There will doubtless be a lot of opinions!

 

[scottf200]

"The true measures for any performance EV driver are acceleration times and driving performance of the vehicle." -- JB Straubel

 

[Cosmacelf]

Bottom line, there are no standards yet for dual motor EV horsepower measurements, Tesla used one way of measuring that doesn't reflect real world power output.

Coming from the computer world where hard drive manufacturers publish really high IOPS specs, and real world testing under various methodologies gives five different numbers depending on how it is tested, this isn't surprising.

But I do agree that it would have been nice if Tesla had used a HP number that was closer to what you could get in the real world.

 

[dsm363]

Bottom line, there are no standards yet for dual motor EV horsepower measurements, Tesla used one way of measuring that doesn't reflect real world power output.

Coming from the computer world where hard drive manufacturers publish really high IOPS specs, and real world testing under various methodologies gives five different numbers depending on how it is tested, this isn't surprising.

But I do agree that it would have been nice if Tesla had used a HP number that was closer to what you could get in the real world.

Totally agree with this. Using a more real world number would have been better but as you noted, using an idealized set of testing isn't new to Tesla. They addressed how they got this number and this will have to do. No free hardware upgrades coming it looks like.

 

[jaguar36]

No horse in this race, but that came across as side-stepping the real issues owners are bringing up (some of which are mentioned in the comments)

Agree, It very rarely even mentioned the P85D going so far as to list HP measurements of the other models but then skipping the P85D. I also got a rather condescending tone from the post. The whole HP isn't relevant for power thing. Its the same unit in a different system.

 

[Todd Burch]

ICE vehicles may be able to achieve their peak number, but that's not all that useful either--peak horsepower occurs at such a narrow RPM range.

I'd rather have a lower peak HP number but a much wider torque band (as EVs provide) than a higher HP number only valid within a narrow band

 

[AnOutsider]

Wouldn't the cleanest solution be to dyno the car and then you can report the peak HP?

 

[stopcrazypp]

However, most HP figures for vehicles are the peak ratings for what the system as a whole is capable of under ideal conditions. Even if an ICE engine itself is capable of 400HP, you can't publish that if the fuel pump is only capable of delivering 350HP worth of fuel rate.

Under most current convention that is true because almost all automakers have switched to SAE net. However, this was not true back when automakers were using SAE gross. Under SAE gross the only thing that had to be stock was the engine. All the rest does not have to be stock, so the numbers do not consider the system as a whole.
http://ateupwithmotor.com/terms-technology-definitions/gross-versus-net-horsepower/

I should note that Fisker also used a similar rating as Tesla (only considered the motors in its 402 hp rating, when in reality it was making under 300 hp considering the whole system). Ford also lists separate motor power numbers for their Energi cars (although they also list battery power now). There is no published SAE power standard yet for EVs.

Also, what JB Straubel said was exactly what I suspected Tesla's rating to be (that it didn't factor in battery power). It was what this article back in October 2014 said it was when the new motor power numbers came out:
http://www.greencarreports.com/news...ower-numbers-for-tesla-model-s-whats-the-deal

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Agree, It very rarely even mentioned the P85D going so far as to list HP measurements of the other models but then skipping the P85D. I also got a rather condescending tone from the post. The whole HP isn't relevant for power thing. Its the same unit in a different system.

I should once again remind everyone of the history of the "motor power" numbers. Starting in October 2014 (with the launch of the dual motor numbers), Tesla published only motor power numbers for all models. It was not until April 2015 (a month after that "691 hp" complaint thread) did they started adding back system power numbers for the other models (although they left it blank for the P85D, but I think the reason why they did was obvious given the thread).

 

[scaesare]

ICE vehicles may be able to achieve their peak number, but that's not all that useful either--peak horsepower occurs at such a narrow RPM range.

Sure, but it's a measurable and achievable number. And it's similar to other specs (like MPG, battery pack range, etc...) that are "optimistic" under many real-world conditions...

I'd rather have a lower peak HP number but a much wider torque band (as EVs provide) than a higher HP number only valid within a narrow band

And many ICE performance enthusiasts make the same point: "It's the swept area under the curve that matters.", which is not without merit, but also has some drawbacks.

Whatever the spec, however, I argue the car should be able to achieve it.

 

[jcoverton]

This debate reminds me of the issues companies had measuring the output of amplifiers. Most amps are measured in watts. Manufactures competed by publishing increased watt ratings in response to demand for bigger amps. Stereo amp manufactures added the output of there two channels together to get total watts in many cases ignoring the fact their power supplies could not drive both channels at the specified wattage. It got worse with home theater systems 5 or more channels. Even as power supplies got bigger, many did not respond well to changes in power demands typical with music reproduction. In the end it was the ability of the system to reproduce music that counted not an amps specifications that could be manipulated.

I think the same is true with the MS. It is how it drives and how quickly it accelerates that counts not the HP ratings or the motors. I have followed this forum for quite awhile and from what I read most people who drive or ride in a Tesla love their cars. I have a P90D being delivered next week and can't wait even though I may never know how many HP it really has or what the total power the electrical system can supply.

 

[sandpiper]

This debate reminds me of the issues companies had measuring the output of amplifiers. Most amps are measured in watts. Manufactures competed by publishing increased watt ratings in response to demand for bigger amps. Stereo amp manufactures added the output of there two channels together to get total watts in many cases ignoring the fact their power supplies could not drive both channels at the specified wattage. It got worse with home theater systems 5 or more channels. Even as power supplies got bigger, many did not respond well to changes in power demands typical with music reproduction. In the end it was the ability of the system to reproduce music that counted not an amps specifications that could be manipulated.

I think the same is true with the MS. It is how it drives and how quickly it accelerates that counts not the HP ratings or the motors. I have followed this forum for quite awhile and from what I read most people who drive or ride in a Tesla love their cars. I have a P90D being delivered next week and can't wait even though I may never know how many HP it really has or what the total power the electrical system can supply.

100% agree!

 

[andrewket]

I've stayed quiet throughout this entire situation. (Well, I think I might have replied once to a post.) I'm still going to stay out of this, but ..

I would have appreciated JB stating when the L upgrades for the older P85Ds would be available. It's been awhile now and the SCs still don't have any information.

 

[Johan]

This debate reminds me of the issues companies had measuring the output of amplifiers. Most amps are measured in watts. Manufactures competed by publishing increased watt ratings in response to demand for bigger amps. Stereo amp manufactures added the output of there two channels together to get total watts in many cases ignoring the fact their power supplies could not drive both channels at the specified wattage. It got worse with home theater systems 5 or more channels. Even as power supplies got bigger, many did not respond well to changes in power demands typical with music reproduction. In the end it was the ability of the system to reproduce music that counted not an amps specifications that could be manipulated.

I think the same is true with the MS. It is how it drives and how quickly it accelerates that counts not the HP ratings or the motors. I have followed this forum for quite awhile and from what I read most people who drive or ride in a Tesla love their cars. I have a P90D being delivered next week and can't wait even though I may never know how many HP it really has or what the total power the electrical system can supply.

This is a great analogy, and one that I think Tesla could really help explain how the horsepower number is similar to the wattage of a given speaker while the torque, acceleration and driving feel is the equivalent of what actually has real mening which in your example would be different aspects of the music being outputted: for example volume/power, dynamic range, responsiveness, corectness in amplifying the original signal (CD, Tape whatever) and in the end the total subjective feel of the totality of the music.

 

[brianman]

Good that they've come out publicly (blog) on the topic. I find the post a bit lacking though, unfortunately.

As an example, the number 691 never appears in the post. That's pretty telling all by itself.

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Another quick note:
Tesla All Wheel Drive (Dual Motor) Power and Torque Specifications | Tesla Motors

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.

To me this begs a follow-up question:

With the new (Ludicrous generation) fuses, you've improved the transfer of power from the batteries to the motors significantly.
When do you expect to be able to deliver a battery that can meet or exceed the demands of the P85D/P90D motors? By 2025? What other weak points in the system -- besides the battery -- are obstacles for achieving 691 / 700+ hp for 10 second bursts (at 30mph)?

Aside from what this means to current customers, I'm quite curious from a technical perspective.

 

[TexasEV]

Could someone explain why anyone cares what the number is? How does it affect your enjoyment or use of the car?