Torque. Lots of torque, right off the line. That one benefit presented by an electric motor over its internal-combustion sibling, and the Tesla Model S delivers it in spades. 443 spades, to be precise, or about as much as a Bentley Continental GT or McLaren 12C. But when one Emmanuel Chang put his electric sedan on a dyno up (way up north) in Edmonton, Alberta, it registered a whopping 2,000 pound-feet!

Of course that number isn't correct, as no car on the road produces that much torque. Even a Bugatti Veyron produces "only" 1,000 lb-ft, give or take. Clearly something's amiss here, but the problem the dyno had in reading the Tesla's torque apparently doesn't come down to its electric powertrain. (Nor does it have anything to do with the northerly latitude or the interference of polar winds.) It comes down to the shiny, ten-spoke alloys.

Apparently this type of dyno measures torque by running horsepower and wheel revolutions through an algorithm. It measures horsepower at the wheel (which, at 436 hp, wasn't far off of Tesla's own rating of 416 hp) and uses a stationary optical sensor interfacing with a reflector on the wheel. Every time the reflector passes the sensor, it counts one revolution. But since the Model S has shiny ten-spoke wheels (and we presume because it was taken outdoors under bright sunlight), the sensor thought that each passing spoke was one revolution of the wheel... when it was, in fact, ten times too much.

The machine can set to compensate for up to a quarter rotation, but not a tenth. And since the software can only calculate up to 2,000 lb-ft, that's the number it spat out. Watch the video to see the Tesla on the dyno.

UPDATE: Turns out there is a lot of discussion on why the dyno registered its overzealous figure. The explanation above comes courtesy of a commenter on Jalopnik, later quoted by DragTimes, who claims to be an engineer at Dynojet, other explanations include the effects of torque multiplication at the wheels and the fact that the Tesla has one single gear instead of a multi-geared transmission. We're not dyno experts, and we don't claim to know which explanation is correct. In any case, the video is interesting, and you're welcome to watch it above.


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    • 1 Second Ago
  • 40 Comments
      Rotation
      • 4 Months Ago

      2,000 lb-ft is not a lot of torque at the wheels. It certainly has that much.

      Conventional torque measurements are at the shaft of an engine. This is multiplied up by the gearbox and the differential.

      My Cadillac has a "mere" 332 lb-ft of torque. It has a first gear gear ratio of 4.06:1 and a differential final drive of 3.42:1.

      So in first gear, it develops 332 * 4.06 * 3.42 or 4610 lb-ft of torque at the wheels.

      A road-dyno like this measure force at the wheels, this is divided by the radius of the wheel/tire combo to determine torque at the wheels. If you want to know torque at the motor shaft you enter the final drive ratio and the gear ratios and it divides by those.

      You can do the same on this car if you want to calculate the torque at the motor output. But it doesn't produce a terribly meaningful number. Given it has no gearbox, an EV like this could easily produce 1,000lb-ft of torque at the motor and still accelerate slower than my measly V6 Cadillac because it doesn't have a gearbox to multiply it. You'd look at 1,000lb-ft, think "wow" and then see the thing creep off the line.

      You either have to compare at a place where shaft speeds are similar (input to the differential) or just compare horsepower, because it takes into account different shaft speeds.

      Ideally, we'd compare force at the wheels, removing all the gear ratios and the implicit gearing of different wheel sizes too. It'd be great to move in that direction but I doubt if that's going to happen.

      So again, stick to horsepower, it's the most fool-proof number. Which is why it's so popular.

        AcidTonic
        • 4 Months Ago
        @Rotation

        Came here looking for a post like this.  Satisfied.

        I was hoping someone would debunk the whole "if it had 2000ft/lb it would spin the wheels" comment.

        Waterwheels have much more torque than that.... but something keeps them from spinning really fast despite moving with lots of torque.... ;)

        bll
        • 4 Months Ago
        @Rotation

        I don't think you understand just how much 2000 lb/ft of torque is.If your cadillac developed 4610 lb/ft of torque in any gear the whole drive train would snap like a twig.A 15 litre 600 cummins makes 2050 lb/ft of torque and that's an engine you find in a Peterbilt or class 8 size heavy duty truck.

          SublimeKnight
          • 4 Months Ago
          @bll

          You didn't understand a word he said, did you?

          m_2012
          • 4 Months Ago
          @bll

          So much fail. PLEASE go read about gear ratios and transmissions. 4000 lb/ft to the wheels is typical for a car. 2000 lb/ft would be an econobox like a Spark. 

      Jake
      • 4 Months Ago

      So, someone experienced measurement error and that was a story? 

        Avinash Machado
        • 4 Months Ago
        @Jake

        Anything for page clicks.

        dfkd
        • 4 Months Ago
        @Jake

        Pretty sure your phone or browser's back button still works...

        G Prodigy
        • 4 Months Ago
        @Jake

        The other blog sites say its b/c of the Tesla's Transmission being one gear.


        this is the first i've heard about it just being b/c of the 10spoke rims..which is a pretty lame story. 

      gslippy
      • 4 Months Ago
      Lots of cars have 10-spoke wheels.  This isn't even a story, except that the guys running this portable dyno don't know what they're doing.
      LabRat
      • 4 Months Ago

      Silly blog-writer, cars have transmissions!

      I'm sorry, Mr. Noah Joseph. How are you able to be a writer in an automotive blog if you don't understand the concept of a transmission? You see there is this incredible device between the prime mover and the wheel that allows for a better match between torque and speed requirements.

      2,000 ft-lbs is not a lot of torque at the wheel! The 1.5L Honda Fit provides over 1,800 ft-lbs of torque at the wheel in 1st gear. Let me step you through it. The Model S has 443 ft-lbs of torque and a single-speed gear reduction of 9.73, which provides 4310 ft-lbs of torque (exactly what the guy in the video said).

      The reason the torque is so much higher than the dyno is used to seeing is that if you are going for max power you do it in a reasonable gear number (3rd or 4th perhaps). The Tesla only has one gear so at lower speeds the load calculation may have been pegged at 2000.

      Please add an UPDATE to your story to apologize for general state of journalism in today’s cesspool of hack writing click-bait.

      m_2012
      • 4 Months Ago

      443 lb/ft * 9.73 gear ratio. I don't see the problem other than a wimpy dyno, clueless operator, and lackluster reporting of a 'story'.

      The dyno only measures torque and speed. Horsepower is calculated by definition. 

      Wilco
      • 4 Months Ago

      Another problem with this explanation, if the rpm counter counted every spoke as a revolution, it was over-reading by 10x. 

      Horsepower = Torque x RPM

      Horsepower is correct, RPM is 10x out.

      Horsepower = Torque / 10 x ( 10 x RPM)

      Thus we can see that measured torque would be 1/10th of the actual value, not 10x.

      A nice attempt at explaining torque and horsepower, but completely wrong on multiple levels. Is it april fool's day?

        kalortpor
        • 4 Months Ago
        @Wilco
        I have no idea who provided the spoke explanation, but as has been pointed out, the car has 9.73 reduction gearing so that's where the 10x comes from, though the dyno maxes out at 2,000 anyway.....Sounds like someone was having fun at the author's expense with the bogus spoke explanation
        LabRat
        • 4 Months Ago
        @Wilco

        Wilco, you are exactly right. I had to check the date (April 1?) as well. Everything about this article is dumb. Several of the replies are dumb. We are doomed! Say it with me "I see dumb people"

      edward.stallings
      • 4 Months Ago

      There is some other explanation perhaps, but dynos measure torque and calculate hp using rpm and the formula  HP = Torque x RPM ÷ 5252.   I would like to know how a dyno can measure hp directly since they can only measure a force (torque) in my experience.  Not expecting any technical insight from Noah.

      Ron
      • 4 Months Ago

      "Tesla Model S delivers it in spades. 443 spades, to be precise, or about as much as a Bentley Continental GT or McLaren 12C."


      Or your average 35k Mustang GT.... 

        kalortpor
        • 4 Months Ago
        @Ron
        A 4600lb Tesla MS (a 5-7 seater sedan with lots of storage capacity) vs. 3000lb Lamborghini Gallardo LP 570-4 (purpose-built race car) was in the lead for nearly a whole 1/4 mile, limited only by the single-speed transmission which makes most sense to have for 99.9% of owners. It still finished respectably and does a 12 second 1/4 mile in spite of having one gear. Does your average 35k Mustang GT hit 0-60 in 3.9 seconds and stay ahead of or right at the nose of GT-Rs and 911s (even more so from a 5 mph roll) under 100mph, and at an equivalent 90mpg?
      icemilkcoffee
      • 4 Months Ago

      Are you sure? I believe the 2000ft.lb reading is in fact, correct. An electric motor produces its peak torque at 0 rpm. The torque declines linearly as rpm rises, until it reaches 0 torque at its maximum rpm. So it is entirely possible that the Tesla produces 2000ftlb at 0 rpm.

        bc3091
        • 4 Months Ago
        @icemilkcoffee

        But the Tesla's electric motor is not capable of 2000 lb-ft of torque. If it had that much torque, it would spin out the rear tires any time you tried to pull away from a stop sign/light. You're correct that the torque is available from 0rpm, but incorrect about how much torque the Tesla can produce.

          kalortpor
          • 4 Months Ago
          @bc3091

          You can't spin the wheels unless you turn the traction control off.....One of the benefits of EV drivetrains is near instantaneous traction control which works wonders in slippery conditions, also helped by the low center of gravity and weight balance in a Model S. The car does 0-60 in 3.9 seconds,  you could already spin the wheels with the power it has now (with TC off).

      Bradford
      • 4 Months Ago

      I don't buy that explanation.  Plenty of rims are shiny.  Does this mean you can only accurately use this dyno if you have matte wheels?  That would be a very strange restriction.

      jebibudala
      • 4 Months Ago

      I wasn't aware of this reflector measuring system they speak of.

      chrismcfreely
      • 4 Months Ago

      A dyno is not a thing that exists on a flatbed. 

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