P85D motor hp controversy starts also to show in U.S. media

[MuppetOwl]

I did email a question to UNECE about the UN Regulation No. 85 if Tesla is allowed to just add together the max power net numbers and if the test include battery limitation. This is the answer.

Thank you for your query about UN Regulation No. 85.
My understanding is that UN Regulation No. 85 (particularly Annex 6 dealing with the method for measuring net power and the maximum 30 minutes power of electric drive trains) is not clear enough at this stage to provide a clear answer to the question. The informal working group Electric Vehicles and the Environment (EVE) under the Working Party on Pollution and Energy (GRPE) is actually currently working on the proper determination of net power of new powertrain technologies such as hybrid electric and full electric vehicles.

However, please note that the secretariat is not authorized to interpret UN Regulations and/or the 1958 Agreement itself.
Such interpretations are fully in the purview of the Contracting Parties to the Agreement and, if they wish, they may bring the question to the World Forum for Harmonization of Vehicle Regulations (WP.29) for consideration and advise.

Thus, you may want to contact the Type Approval Authority and the Technical Service granting such approvals to give you their interpretation of the Regulation.

 

[yak-55]

Yes, if the front motor was running at max power, the P85D as a total can only output 50hp more than the 85D because of the battery, however in the case of torque sleeping the front motors, the P85D can output 200+ more hp on the rear motor. This difference would not be represented in a system number.

(some material deleted for brevity)

With just system power number, the P85D only gets a ~60hp advantage over the P85 and 85D, but then Tesla doesn't get to illustrate how versus the P85 you are actually getting an additional 221hp motor in the front. With 85D, they don't get to illustrate the P85D rear motor is 200+hp more. I think that is why they used motor power.

Now with 20/20 hindsight, we can say that what should have done was advertise with a system number, and then the individual motor power numbers not combined together, which is what they are doing now (P85D is still missing system number and I already put the theory of the exception being there precisely because of P85D complaining). However, if you were a marketing manager back then, it would not be obvious this would be as big an issue for some people as we now know. And adding the two numbers is very intuitive too.

No hindsight is required. Tesla was no doubt in possession of all these facts at the time. Their marketing choices, in the face of these facts, stand in the historical record.

Hardly relevant, but if *I* were "a marketing manager back then" *I* would very much have known this would be a big issue. *My* proposal to show real world relevant system power numbers probably would have been shot down as "not conducive to hitting our P85D revenue and margin goals. Everyone will just buy 85Ds ..."

To Tesla's credit, they have made some recent improvements in their disclosure. However, they have (almost tortuously) avoided any accurate representation of the real world power differences between the P85D and other comparable vehicles. Potentially damaging the brand. Why roll around in the questionable practices of the industry if you're goal is to be a different kind of car company?

 

[AmpedRealtor]

It's not that hard - the motors are capable of 691hp but the battery doesn't have enough juice to let them produce more than 550hp in ideal conditions. The car can go 50,000 miles on a single charge, but the battery will run out of charge in 200-300miles, depending on driving conditions. No electrical engineering degree required to understand.

Too bad Tesla doesn't explain it this way on its web site. Too bad owners have to seek out answers and look up regulation ECE XYZ12345 in order to understand that the numbers Tesla prints on its web site are, for lack of a better word, crap. Don't give Tesla the idea of marketing the range as 50,000 miles because I believe Elon would do so if he thought he could get away with it.

 

[dsm363]

Please enlighten me with a few examples in RECENT history of automobiles that a ICE car couldn't produce the stated HP at ANY part of the car, AND the discrepancy was as big as 15-20%. It's not unexpected that we can't recreate the exact nitpicky conditions the carmaker uses to produce their stated spec ---- we might not be able to reproduce the maximum ranges stated for model S, that is quite okay, but it's totally a different matter that the car is IN THEORY incapable of and far from producing that spec, which is exactly the case for P85D.

Can you name another car with a front and rear motor blended into an AWD platform?

 

[Soolim]

Can you name another car with a front and rear motor blended into an AWD platform?

Porsche 918 comes to mind:
Gas engine rear = 608 hp @ 8700 rpm
Rear electric motor = 156 hp
front electric motor = 129 hp
Max system hp = 887 hp
0-60mph = 2.5 seconds
1/4 mile = 10 seconds @ 145 mph
top track speed = 214 mph

 

[gavinwang]

Porsche 918 comes to mind:
Gas engine rear = 608 hp @ 8700 rpm
Rear electric motor = 156 hp
front electric motor = 129 hp
Max system hp = 887 hp
0-60mph = 2.5 seconds
1/4 mile = 10 seconds @ 145 mph
top track speed = 214 mph

Thanks for jumping in, I was about to say the same. Many hybrids have two or more power units, one being an electric motor, the other a gas engine. BMW i8 has two electric motors plus one puny engine. Nonetheless, I have no clue what dsm363 meant to say.

 

[sorka]

My point was that whereas the screen resolution represents what you see as an end user, the HP number quoted doesn't. For example, while the P85D loses 10% of its power by the time it reaches the wheels, a typical AWD ICE car is assumed at 35% loss.

20% to 25% *used* to be typical numbers thrown around for AWD drivetrain loss years ago. I've never EVER seen anyone claim higher than that so I'd like to know where you found 35%?

For comparison, stock RS7's dyno around 470 at the wheels SAE corrected which puts them at about 16% loss. AWD ICE cars have come a long ways in the last decade with much more efficient gear designs and automatic transmissions that lose a fraction of what they used to due to better fluids that are lighter and thinner yet protect better...as well as other design improvements that increase efficiency.

Also, we need to be very careful when discussing power train loss from the engine to the wheels. Loss comes from two sources. 1) Friction losses(gears, fluid resistance, tire deflection, etc), and 2 ) intertial losses(the energy it takes to accelerate or decelerate drivetrain mass).

Dyno runs at static speed under an eddie current load will completely hide losses due to inertia as the dyno is measuring the amount of power to keep the engine at it's exact peak power RPM. In this kind of dyno, if you change a flywheel from a heavy to a lightened one, the dyno will not register this as a power increase because there's no change in speed and as such no acceleration of mass. But on a dynamic dyno run where you accelerate drivetrain mass, a lightened flywheel will show as more power. The less the load that the drivetrain has to push against, the faster the drivetrain will accelerate causing the proportion of friction loss to inertial losses to shift more towards inertial losses as intertial losses increase as you reduce the load against the drivetrain on the dyno. The percentage of drivetrain loss measured is the least on static runs because you *only* have he frictional losses. This is why rule of thumb losses are meaningless.

The P85D has much less drivetrain mass compared to the typical AWD ICE. As such the P85D has an advantage in an acceleration dyno run compared to the ICE that makes the same power because the P85D's drivetrain doesn't have to overcome as much inertia. This advantage disappears once you dyno both cars at a static speed (where both are making their peak power) but not accelerating mass.

- - - Updated - - -

I did email a question to UNECE about the UN Regulation No. 85 if Tesla is allowed to just add together the max power net numbers and if the test include battery limitation. This is the answer.

Holy smokes! You got an answer? Who exactly did you email? I emailed nearly the same question to [email protected] twice and never got a response. The first part of that response is quite eye opening!

 

[dsm363]

Thanks for jumping in, I was about to say the same. Many hybrids have two or more power units, one being an electric motor, the other a gas engine. BMW i8 has two electric motors plus one puny engine. Nonetheless, I have no clue what dsm363 meant to say.

I meant to ask how they write the combined hp down. If the full hp of the ICE and electric motor are available at one time how do they advertise it? Is it the hp at the shaft?

 

[X-Wing]

Can you name another car with a front and rear motor blended into an AWD platform?

Mid-Engine ICE / F & R Electric

Porsche 918
Acura NSX

Front ICE / Rear Electric

Acura RLX
Volvo XC90

Could they both be using the e-AAM eAWD technology?

Front and Rear Electric (Torque Vectoring Capable)

SLS AMG E-Cell
Porsche Mission E

The SLS AMG was supposed to go into production, not sure if any ever did. Basically the SLS AMG E-Cell and Porsche Mission E are the Germans signaling that they have not been slacking in the EV game.

 

[dsm363]

Do they advertise the correct system hp at the shaft that the car can actually achieve is my question.

 

[X-Wing]

I meant to ask how they write the combined hp down. If the full hp of the ICE and electric motor are available at one time how do they advertise it? Is it the hp at the shaft?

The system power is measured based on the combined simultaneous output of both powertrain.

Note that the peak system output does not necessarily have to occur at either peak ICE or EV output.

Gear ratio also needs to be factored in. But let's assume that both the ICE and EV have just one single gear. The peak system output in this case is 82HP at 60mph.

Vehicle Speed	ICE (hp)	EV (hp)	System (hp)
50mph	30	50	80
60mph	41	41	82
70mph	50	30	80

As to Tesla, Volvo XC90 or Koenigsegg Regera. The actual combined power is less than the combined max individual motor power. Which could look something like this.

Vehicle Speed	Front (hp)	Rear (hp)	System (hp)
10mph	50	100	150
30mph	100	200	300
50mph	75	300	375

In the above example, the combined motor power is 100+300 = 400 hp. But the system power is only 75+300=375hp.

The specific case with the P85D/P90D is probably more complicated, as that is limited by the output of the battery which is totally outside of my area.

To me a better analogy to this debate is if a manufacture ships an engine physically capable of making 1000hp, but had to be de-tuned to 700hp because the fuel pump and injectors cannot keep up. Can the manufacture still claim making 1000hp?

 

[vgrinshpun]

I did email a question to UNECE about the UN Regulation No. 85 if Tesla is allowed to just add together the max power net numbers and if the test include battery limitation. This is the answer.

I am curious what was the question you asked in the e-mail - I think you should share it along with the response.

Regarding the answer, it is not clear why the responding person is focusing on Annex 6. Annex 6 is laying out the rules for testing drive train, and it does not make distinction of whether the drive train includes one or several motors. Annex 2, however, implies that a drive train could either have one or more than one motor:

 

[AWDtsla]

To me a better analogy to this debate is if a manufacture ships an engine physically capable of making 1000hp, but had to be de-tuned to 700hp because the fuel pump and injectors cannot keep up. Can the manufacture still claim making 1000hp?

If a manufacturer ships a car that claims 1000hp, and there is no legal speed at which it has the traction on any road to output that 1000hp, can they still claim 1000hp? *cough* hellcat *cough*. Should return it back to Dodge "I press the pedal but I don't accelerate like I have 707hp, I just see smoke"

 

[X-Wing]

If a manufacturer ships a car that claims 1000hp, and there is no legal speed at which it has the traction on any road to output that 1000hp, can they still claim 1000hp? *cough* hellcat *cough*. Should return it back to Dodge "I press the pedal but I don't accelerate like I have 707hp, I just see smoke"

Completely different argument. Yes, Dodge can claim 707hp because they are producing 707hp.

At exact what vehicle speed does the P85D produce a combined 691hp from both motors?

 

[vgrinshpun]

Do they advertise the correct system hp at the shaft that the car can actually achieve is my question.

And the answer is no. Both MB SLS Electric and Porsche 918 list combined maximum power of the motors without considering limitation of the battery, exactly the same way as motor hp is listed by Tesla.

I've posted about the SLS here.

Regarding the Porsche, it lists combined motor horsepower as 286 (129+156+rounding error). It has 6.8kW battery, which will not be able to provide output of 286hp or 213kW, as it will require discharge at the rate of 213/6.8=31.3(C), which is way too high for the automotive application. For comparison Tesla maximum discharge rate is under 5C. Additionally, it is clear that two electric motors in Posche 918 can't deliver the combined output of 286hp because they are limited by the tiny 6.8kWh battery - the car electric only speed is limited to 93mph (car weights 3692lbs).

So it appears that the way Tesla listed motor horsepower is not only consistent with ECE R85, but is also consistent with the way other manufacturers (Porsche, Mercedes) list motor hp for EV multi-motor drivetrains.

 

[AWDtsla]

Completely different argument. Yes, Dodge can claim 707hp because they are producing 707hp.

At exact what vehicle speed does the P85D produce a combined 691hp from both motors?

No, it's completely the same argument, unless your only application and single-minded focus on this one number is for a pissing contest.

The phrase dyno queen exists for a reason.

 

[supratachophobia]

The system power is measured based on the combined simultaneous output of both powertrain.

Note that the peak system output does not necessarily have to occur at either peak ICE or EV output.

Gear ratio also needs to be factored in. But let's assume that both the ICE and EV have just one single gear. The peak system output in this case is 82HP at 60mph.

Vehicle Speed	ICE (hp)	EV (hp)	System (hp)
50mph	30	50	80
60mph	41	41	82
70mph	50	30	80

As to Tesla, Volvo XC90 or Koenigsegg Regera. The actual combined power is less than the combined max individual motor power. Which could look something like this.

Vehicle Speed	Front (hp)	Rear (hp)	System (hp)
10mph	50	100	150
30mph	100	200	300
50mph	75	300	375

In the above example, the combined motor power is 100+300 = 400 hp. But the system power is only 75+300=375hp.

The specific case with the P85D/P90D is probably more complicated, as that is limited by the output of the battery which is totally outside of my area.

To me a better analogy to this debate is if a manufacture ships an engine physically capable of making 1000hp, but had to be de-tuned to 700hp because the fuel pump and injectors cannot keep up. Can the manufacture still claim making 1000hp?

If a manufacturer ships a car that claims 1000hp, and there is no legal speed at which it has the traction on any road to output that 1000hp, can they still claim 1000hp? *cough* hellcat *cough*. Should return it back to Dodge "I press the pedal but I don't accelerate like I have 707hp, I just see smoke"

Yes, because the system still outputs the advertised 707hp, 6 times during it's acceleration curve.

The Tesla does not, as shipped, with either battery option.

 

[X-Wing]

No, it's completely the same argument, unless your only application and single-minded focus on this one number is for a pissing contest.

The phrase dyno queen exists for a reason.

Clearly you have problem comprehending some of the concepts involved. A Dodge Charger Hellcat makes 707 SAE horsepower at the following vehicle speeds, according to FCA. Of course that is 707 HP at the crank.

Gear	Gear Ratio	Final Ratio	Overall Ratio	Engine RPM	KM/H	MPH
1st	4.71	2.62	12.34	6000	66.72	41.47
2nd	3.14	2.62	8.23	6000	100.08	62.20
3rd	2.1	2.62	5.5	6000	149.65	93.01
4th	1.67	2.62	4.38	6000	188.18	116.95
5th	1.29	2.62	3.38	6000	drag	limited
6th	1	2.62	2.62	6000	drag	limited
7th	.84	2.62	2.2	6000	drag	limited
8th	.67	2.62	1.76	6000	drag	limited
Reverse	3.3	2.62	8.65	6000	95.23	59.19

Keep in mind that Tesla does have a single speed gearbox with reduction gear and by virtual of that design has minimal drive train lost.

But we are not arguing about wheel horsepower here, we are talking about system power of the two motors working in combination with their respective reduction gear ratio.

Once again, educate me please. At exact what vehicle speed does the P85D produce a combined 691hp from both motors? To clarify 691 combined horsepower from the electric motor right before said power is fed into their respective single speed gearbox. Just like the 707 horsies from the Hellcat right before said power is fed into the ZF 8-speed gearbox.

 

[stopcrazypp]

Please enlighten me with a few examples in RECENT history of automobiles that a ICE car couldn't produce the stated HP at ANY part of the car, AND the discrepancy was as big as 15-20%. It's not unexpected that we can't recreate the exact nitpicky conditions the carmaker uses to produce their stated spec ---- we might not be able to reproduce the maximum ranges stated for model S, that is quite okay, but it's totally a different matter that the car is IN THEORY incapable of and far from producing that spec, which is exactly the case for P85D.

You are changing the argument. Your argument is that it is common sense for a manufacturer to never be allowed to advertise a number it can't produce in any part of the car (or alternatively for them to advertise a number at a component level rather than a system level). I am saying it is not and have given an example in the car world. There is no common sense reason why it is always unacceptable to advertise at a component level.

And in the ICE world, I should point out the convention has switched to SAE J1349 (aka net power) and SAE J2723 (aka certified power). There are no such conventions yet in the EV world and obviously those standards don't apply to EVs (as they assume the existence of an ICE). There are two working groups that are working to come up with one though:
http://standards.sae.org/wip/j2907/
http://standards.sae.org/wip/j2908/

 

[stopcrazypp]

Do they advertise the correct system hp at the shaft that the car can actually achieve is my question.

I think the Fisker Karma can be thrown in there also. Although it is not AWD, the two traction motors are also synchronized through the road. For that I think it is fairly clear that car used the same rating method as Tesla (just added the power of the two motors together: 150kW+150kW = 300kW / 402 hp).

For the only dyno that was done it got 230whp.
http://www.fiskerbuzz.com/forums/13-fisker-karma/4601-maximum-power-karma.html

I think the SLS E-cell is the closest however, but unfortunately there are not enough tests done on that to know if it factors in the battery correctly or not. I don't believe there are even any 1/4 mile or 0-100mph numbers verified for that, much less a dyno.

I should note none of the examples so far they did use the "motor power" term to differentiate what they might be doing.

The examples given by others of hybrids that are synchronized through a gearbox doesn't really apply as we are not talking about gearing imposed limitations, but rather a battery imposed one. The existing SAE standard for ICE is able to factoring in gearing imposed limits, as evidenced by hybrids certified via existing standards:
http://standards.sae.org/cpgm2_latsaturn/
http://standards.sae.org/cpgm2_10tyesshy/