Tesla blog post: AWD Motor Power and Torque Specifications

[mgboyes]

I think a huge portion of the problem is that, while Tesla and wk057 know the actual output of the battery, the inverters, and the motors, Tesla lives in a world where they compete against ICE vehicles that are rated differently because their systems are different. Even though there is a direct mapping of kW to hp, that doesn't capture the qualitative difference between Tesla's drivetrain and ICE competitors. For example, there was that UK review where they compared an Aston Martin with a P85 and the P85 was very much quicker even though the Aston has something like 550 hp. Tesla has to sell against these ICE vehicles all the time where the hp numbers do show up somewhere in the drivetrain but never really makes it to the road. So they chose a spec that is true in some sense, but misleading. But it better captures the qualitative experience - an ICE vehicle with 550 hp usually doesn't accelerate like a P85D with the curb weight of the P85D.

Sorry not sure I buy this.

The Mazda RX-8 has a 1300cc rotary engine that performs like a 3 liter V6, but Mazda didn't just decide arbitrarily to declare a different engine capacity to help their marketing department out. They made a feature of how amazing their rotary engine technology is that such a compact unit can generate that much power and rev so freely.

Tesla should be doing the same. If a P90DL with 500bhp can beat an Aventador 0-60 because the Aventador's drivetrain belongs in a museum of Victorian engineering, then that's something to be proud of, not something to cover up by pretending the Model S does it just by having more power.

It's not like Tesla are trying to win over muscle car drivers anyway - the sort of person who looks down on a car because it "only makes 550bhp" is unlikely to be buying a Model S in the first place.

Also the 911 Turbo S only makes about 550bhp and it's just about the only car you can buy for less than crazy money that can keep up with a P90DL 0-60.

 

[wk057]

The analogy is not 100% perfect, but the crux of the analogy is that under SAE Gross power, the number given is supposed to reflect the engine, not the system as a whole. This is similar to how "motor power" focuses on the motor. The difference between gross power and net power is 25-30% (sometimes higher). The difference between the motor power 691hp and the battery power at 550hp is 20%. If you throw in inverter/motor losses then it'll pretty much be in the 25-30% range. The analogy seems like a good fit to me.

The fuel analogy you use doesn't work that well, because in all cases, whether it be a power supply, the stock battery, a custom battery, or some other DC source, all of them is using electricity. All the motor inverter cares about is getting that DC electricity (the motor cares about getting the AC). Whereas an engine is very different running different fuels.

This is not obfuscation, just an observation that for a better part of a century (until the switch to net power starting in the 1970s), this was a horsepower standard that was accepted by everyone and has similar implications as Tesla's "motor power" rating. This is a counterpoint to those that claim that all horsepower standards for cars must reflect the system as a whole.

Straubel also seems to be saying the current European standard is similar.

What he said is completely true. There is a noticeable section in the rev range of the motors where the available battery power is more than the motors can output. When it reaches ~40mph, that is when the power "plateaus" in the P85D and the battery is the limiter. That is the "often" part.

I think you guys are overly focused on looking only at the peak power and forget that the power band is not just represented by one number.

((( EDIT: My previous post wasn't deleted as I had thought, it was placed in a "moderation queue" without anyone saying so. To mere mortal like myself it simply appears to be deleted. My apologies to the moderators. )))

This post is yet another obfuscation attempt that might work on people who don't know what you're talking about, just like JB's post. You add no relevant information to the topic and are simply grabbing two small portions of my in-depth post in an attempt to discredit the information I provided by throwing out things that have no bearing on the topic. As mentioned in my post which disappeared, Tesla should definitely hire people like you to support their position on this matter because this post is definitely a prime example of people trying to bury the reality of the situation, just like they attempted to do.

The fuel analogy you use doesn't work that well, because in all cases, whether it be a power supply, the stock battery, a custom battery, or some other DC source, all of them is using electricity. All the motor inverter cares about is getting that DC electricity (the motor cares about getting the AC).

This is laughable. Really? My analogy works perfectly fine, where your attempt to explain it away definitely does not. I mean, sure a bench power supply puts out electricity... just like a nitrous oxide tank puts out a combustible fuel. The "engine" is unchanged in both cases, and can run from whatever fuel source you feed it if it is fed correctly. In an ICE this is something that explodes. (I've personally run an old cabureted ICE car from a hydrogen and oxygen mixture with zero modifications to the stock engine.) In the P85D this is a high voltage high current DC source (assuming you're allowing the inverter, which is physically welded to the motor, to be part of the engine in this case... or have we stooped low enough to be arguing the rating the AC side only?). What you're saying is that Tesla is allowed to choose any fuel that they want in an effort to inflate the actual advertised performance numbers of *the car*, regardless of the performance of the actual fuel used in the real world (the battery's power output). By your logic, Audi, BMW, etc should be allowed to test their engines and advertise power numbers using any fuel they can come up with that gets the best numbers (nitrous oxide is the first to come to mind, but I'm sure there is probably something better) and we should be OK with that.

What he said is completely true. There is a noticeable section in the rev range of the motors where the available battery power is more than the motors can output. When it reaches ~40mph, that is when the power "plateaus" in the P85D and the battery is the limiter. That is the "often" part.

Unfortunately for you, this speaks volumes to your lack of actual knowledge of the subject, or that maybe you do understand and are using that understanding to obfuscate the situation even more. Let's break it down.

Just like Tesla, you've pulled a switcheroo without explaining yourself. You've switched your own defense of "motor power" to now include the limitations of the car, since it suites your obfuscation in this case. The *car* will certainly artificially limit the amount of power flowing to the motors until it is not traction limited (the ~40 mph area you mention). The *motors* have no such limitation and would happily accept their full rated power regardless of traction, if that power were available. Any limitations to the power flowing into the motor are artificially created by software. So, I stand by pointing out the fact that the sentence from the blog post, "With the P85D the combined motor shaft power can often exceed the battery electrical horsepower available," is a lie (misleading at best) since the combined motor shaft power (a static rating) is never less than the battery power available. I'm not sure how math works over there in California, but as far as I know 415 kW or less is always less than 515 kW, not "often" less.

As for SAE ratings, there are pretty good reasons why for the past 40+ years car manufacturers have advertised the actual horsepower ratings of their vehicles. What you're saying is that Tesla should be allowed to ignore that and get away with it.

It's nonsense "explanations" and blind defense of Tesla's position from posters like the above that were a big part of what caused me to step away from actual discussions on this and other topics here on TMC in the first place. It's simply impossible to argue logically with blind allegiance.

In any case, I await further obfuscation to thoroughly debunk. ("Obfuscation" is my new favorite word, can you tell?)

Back off duty for the most part.

 

[WarpedOne]

I do wonder if the cells can output a higher amount of current for a very short period of time.

They can.
But they cannot output that current long enough to be displayed on the dash or measured (deduced) by dynamometer.

 

[bonnie]

Wow, so a mod completely *deleted* my previous reply to this post. Completely deleted. Not moved to snippiness nor any other thread. Completely gone. lol. No PM about it, no post here explaining, nothing. Just gone. I guess I'll re-write my post since apparently someone higher up on this forum is on your side and doesn't want to make that known. This is the first instance where I actually feel censored here on TMC. I'll pastebin it this time also as a precaution.

wk, you know as well as I do that mods don't just delete posts on TMC unless there is a major TOS violation. Major. You also know there have been problems in the past with indexing, etc.Unless you know for a fact that a moderator removed your post, it seems a bit dramatic to scream 'censorship!'. Think you owe them an apology...

 

[wk057]

wk, you know as well as I do that mods don't just delete posts on TMC unless there is a major TOS violation. Major. You also know there have been problems in the past with indexing, etc.Unless you know for a fact that a moderator removed your post, it seems a bit dramatic to scream 'censorship!'. Think you owe them an apology...

Admittedly, my previous response probably was bound for snippiness, but it was in no way a "major TOS violation" by any stretch. If so, then my repost is also going to be removed since it has the same content weaved in.

Up until your post here, I was unaware of any "indexing" issue, and this has never happened with any of my other 3000+ posts. I'm going to venture that this seems pretty unlikely (an obscure technical issue randomly removing a single controversial post out of thousands of others, after it had shown on the thread for an extended time as post #60... or a mod removing it.... occam's razor comes to mind). If it is in fact the case (I have no way to prove either way) then the mods certainly have my apology. (Edit: noted in repost)

 

[bonnie]

Admittedly, my previous response probably was bound for snippiness, but it was in no way a "major TOS violation" by any stretch. If so, then my repost is also going to be removed since it has the same content weaved in.

Up until your post here, I was unaware of any "indexing" issue, and this has never happened with any of my other 3000+ posts. I'm going to venture that this seems pretty unlikely (an obscure technical issue randomly removing a single controversial post out of thousands of others, after it had shown on the thread for an extended time as post #60... or a mod removing it.... occam's razor comes to mind). If it is in fact the case (I have no way to prove either way) then the mods certainly have my apology.

Then it was probably put temporarily in moderation while the mods decided what to do with it, which means it would be temporarily invisible ... but not deleted - when you weave a lot of content in with snippiness content, mods really don't want to take it out of the thread, but can't leave it either. So then they have to split the post or some other messy thing. If (as a mod) you don't immediately put it into moderation, then others quote it in response and you have an even bigger mess to clean up.

So give them a break. I am positive your post is not deleted. Just some cleanup going on. (And not sure how you could have missed ongoing indexing issues. But you clearly did.) Maybe leave out the snippiness next time and avoid the whole situation?

 

[qwk]

the problem is if we simply rated dual motor ev's peak hp as the peak power draw from the battery then two cars with the same hp rating could have massive performance differences, yet the customer would buy the one with the most hp

long term this will be settled on the race track. some ev's may be more suited to drag races and some ev's may be more suited to race tracks. the model s has no competition yet. until there is actual competition in the ev space tesla will continue to spin hp numbers. long term all hp figures will be removed from the tesla website forcing customers to compare actual performance. you have to remember tesla is still an underdog and the people we are at war with do not play fair.

So you think lying to your customers, after saying how much more honest you are from the dealerships is fair? False advertising, and bait and switch is all over the place anymore, but saying you are so much better than that, and then doing the same thing is new to me. Sad really....

 

[wk057]

Then it was probably put temporarily in moderation while the mods decided what to do with it, which means it would be temporarily invisible ... but not deleted - when you weave a lot of content in with snippiness content, mods really don't want to take it out of the thread, but can't leave it either. So then they have to split the post or some other messy thing. If (as a mod) you don't immediately put it into moderation, then others quote it in response and you have an even bigger mess to clean up.

So give them a break. I am positive your post is not deleted. Just some cleanup going on. (And not sure how you could have missed ongoing indexing issues. But you clearly did.) Maybe leave out the snippiness next time and avoid the whole situation?

Mod PM'd confirming it was placed in "moderation queue." So, my apologies. Would be nice if this triggered a notification of some kind to avoid confusion.

If the indexing issue was recent, keep in mind that my activity here has been pretty limited for a bit.

I'll update my post above.

 

[AnOutsider]

Mod PM'd confirming it was placed in "moderation queue." So, my apologies. Would be nice if this triggered some sort of notification of some kind to avoid confusion.

If the indexing issue was recent, keep in mind that my activity here has been pretty limited for a bit.

I'll update my post above.

While you do that, please also clean up language that can be considered snippy. This way, you get your message across, mods have less work to do, and we don't bring down the tone.

Gracias!

 

[wk057]

While you do that, please also clean up language that can be considered snippy. This way, you get your message across, mods have less work to do, and we don't bring down the tone.

My previous post (the one removed/queued) was much shorter and contained no real defense of my position besides saying that the quoted post was nonsense and that I didn't feel like bothering with a detailed response on why, so perhaps snippiness was in order since it didn't particularly contribute. The disappearance prompted my updated post with full defense of my position and I do not consider it to be snippy.

I've heard from the mod, edited my new post to correct the confusion, and am done with OT posts on the matter here.

 

[PhysTom]

Hi Guys,

Using the Ludicrous P85D weight, battery, tire, and gear specs, it can be shown that a combined 649 hp and 713 ft lb of Torque at the road (with some other assumptions) is sufficient to meet the 2.8 sec to 60 mph performance spec with both 100% and 50% SOC. See the post Tesla S 85D Ludicrous Mode Performance Simulation for details of the Simulation Model.

Tom

 

[Gizmotoy]

It's certainly a well-reasoned post by JB and explains their thinking along with much of the technical details we've discerned on our own, but it kind of sidesteps the core issue: Tesla used MAX(Ideal battery horsepower, Ideal combined motor horsepower) instead of MIN() in their advertising. Certainly we're in uncharted waters, here, but it's pretty safe to say that if a vehicle as a whole can't produce the claimed horsepower under any (even ideal) conditions, then you should not be advertising it as such. That's the key point, I think.

Unfortunately all they can do now is hold the line, because doing literally anything else is going to get them sued given there's no fix that allows the car to achieve the claimed horsepower.

The fuel pump analogy posted earlier really drives home the issue, I think.

 

[JonG]

Thei issue is as much about being inconsistent across their cars as it is lack of any standards. They can argue what they like in terms of what their figures mean but to use 1 ft roll out on one car v without rollout for another, to show battery limited on one car (in fact it seems underplay the 85/90D figures) yet try and massage the message on another is exaggerating the performance gap to justify the price gap - just one example of being very misleading and disingenuous.

 

[flathillll]

So you think lying to your customers, after saying how much more honest you are from the dealerships is fair? False advertising, and bait and switch is all over the place anymore, but saying you are so much better than that, and then doing the same thing is new to me. Sad really....

It is not lying if it is halfway true! Haha

The sad reality is consumers have been programmed to buy cars and brag about cars using one number: peak hp

Imagine if Tesla came out with a P90Q with four motors, but it had the exact same battery hp as the P90D. They would be stupid to advertise it using battery hp. People need to stop being naive. Tesla would be stupid to be "honest" in this situation.

Should they also be forced to state the battery hp at 1% capacity? Or maybe the battery hp at the -20C. Or maybe the battery hp when it is in overtemp mode. No motor power is the best correlation to cost. A P85DM could be made with one rear motor and have the exact same battery hp, but use a Mechanical gearbox instead of two motors. Under your proposed system from the average customer perspective they would be the same car. When porsche makes an awd 911 they don't add another motor to the front. Is it also fair the the 918 hybrid gets to state combined system hp even though they use a tiny 6.6kw battery pack that will be quickly depleted. We are in a new world but most people are still living in the past.

 

[qwk]

It is not lying if it is halfway true! Haha

The sad reality is consumers have been programmed to buy cars and brag about cars using one number: peak hp

Imagine if Tesla came out with a P90Q with four motors, but it had the exact same battery hp as the P90D. They would be stupid to advertise it using battery hp. People need to stop being naive. Tesla would be stupid to be "honest" in this situation.

Should they also be forced to state the battery hp at 1% capacity? Or maybe the battery hp at the -20C. Or maybe the battery hp when it is in overtemp mode. No motor power is the best correlation to cost. A P85DM could be made with one rear motor and have the exact same battery hp, but use a Mechanical gearbox instead of two motors. Under your proposed system from the average customer perspective they would be the same car. When porsche makes an awd 911 they don't add another motor to the front. Is it also fair the the 918 hybrid gets to state combined system hp even though they use a tiny 6.6kw battery pack that will be quickly depleted. We are in a new world but most people are still living in the past.

LOL. The issue here is that Tesla flat out lied about the power the car made. It makes nothing close to 691HP. You are trying to justify it by muddying the waters with things that are irrelevant. The car will not make anywhere close to the power advertised with a battery at 100%. That is a fact.

So in your world, people should take it easy on Tesla because there are people out to get them etc., so it's okay for Tesla to lie in order to survive? Awesome logic.

 

[WarpedOne]

The issue here is that Tesla flat out lied about the power the car made

And they are lying from the start and for all their models.

You want proof? Here:

Motoreffekt KW 69 kW

Tesla Model S can only sustain 69 kW of continuous power and even that power disappears after an hour or so.
Any higher number than 69kW can only be output for some shorter time.

It all boils down to dash display. It is to damn slow to show short bursts of X kW.
How high can X go? Depends entirely on dash refresh time.

There is some energy in those wires and capacitors that is 'spent' in microseconds after applying it to the motors.
Even if it is just 2,5 mAs, if it is spent in a microseconds, that results in 1MW of power burst.

Is that not a long enough time to be relevant? What is? A milisecond? A tenth of a second? A second? Ten seconds?

There is no such standard. I agree it would be useful, say 10 second window sounds good.
But than again in a car with 3s 0-60 time those 10 seconds may be to long to distinguish cars that can do 100kW for 10s from those that can do 200kW for 6s and only 50kW after that.
Should we shorten that time down to 5 seconds then? Then it wont say enough about cars that drasticaly drop after 5 seconds.

How do we know there is no 550kW for even tenth of a second? Just because it is not displayed on the dash or in REST log?
What if it does not have enough resolution?

I tell you Model S can output 1MW of power. But for such a short time, one does not notice it.

 

[qwk]

And they are lying from the start and for all their models.

You want proof? Here:


Tesla Model S can only sustain 69 kW of continuous power and even that power disappears after an hour or so.
Any higher number than 69kW can only be output for some shorter time.

It all boils down to dash display. It is to damn slow to show short bursts of X kW.
How high can X go? Depends entirely on dash refresh time.

There is some energy in those wires and capacitors that is 'spent' in microseconds after applying it to the motors.
Even if it is just 2,5 mAs, if it is spent in a microseconds, that results in 1MW of power burst.

Is that not a long enough time to be relevant? What is? A milisecond? A tenth of a second? A second? Ten seconds?

There is no such standard. I agree it would be useful, say 10 second window sounds good.
But than again in a car with 3s 0-60 time those 10 seconds may be to long to distinguish cars that can do 100kW for 10s from those that can do 200kW for 6s and only 50kW after that.
Should we shorten that time down to 5 seconds then? Then it wont say enough about cars that drasticaly drop after 5 seconds.

How do we know there is no 550kW for even tenth of a second? Just because it is not displayed on the dash or in REST log?
What if it does not have enough resolution?

I tell you Model S can output 1MW of power. But for such a short time, one does not notice it.

I don't think you understand how cars work............

 

[wk057]

I don't think you understand how cars work............

I'm going to have to agree. lol.

 

[WarpedOne]

I don't think you understand how cars work............

I would love to hear where I have it wrong.

 

[wk057]

I would love to hear where I have it wrong.

While the detailed information is non-public and not mine to share (although I've been hoping that this person would publish his findings *poke* *nudge*), I know for a fact that the pre-charge capacitors in the Model S drive unit are in no way shape or form capable of delivering 1MW of power to the motors for any amount of time. lol. The battery, under short circuit conditions, could potentially deliver about 600kW before popping every single cell level fuse in the pack instantly.