By on December 22, 2009

torque claims for idiots

It’s going to take a while before the words “EV” and “Idiot” are not inextricably linked with Audi. The company that let it slip that it thought the Volt was “a car for idiots must think we’re idiots too, to swallow their idiotic claim of 3,319 lb.-ft. of torque. We didn’t at the time. Now the truth is out: as some of the commentators then suspected, Audi was using “at the wheel” torque numbers. Thanks to the miracle of gears and their remarkable torque amplifying ways, stating torque at the wheels is about as logical and useful as the Volt’s 230 mpg claim. And EV range claims based on only using the EPA City driving loop. Well, someone took Audi to task, and came up with a confession and a more realistic torque number.

Edmunds Green Car Advisor got Audi to admit that the E-tron puts out a much more realistic 501.5 lb.-ft. at the motor. That compares to the lighter Tesla Roadster’s 273 lb.-ft., which still manages to outrun the E-tron 0-60 by a second or so. So what was Audi thinking?

Audi engineers say they decided to use wheel torque to describe the E-tron’s grunt because it is more reflective of how electric motors deliver their power.

Utter B.S. Put a Jeep with an automatic into low range and first gear, and you’ll have a torque number bigger than a locomotive (pre-reduction, that is). Maybe one of the B&B will do that calculation for us. The automotive industry has never used at the wheel torque numbers, and it’s highly misleading. But there’s an idiot born every minute, and Audi is not going to let us forget it.

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15 Comments on “Audi Busted: Backs Off From Idiotic E-Tron Torque Claim...”


  • avatar
    texlovera

    So the company that hemhorraged sales for, what,  20 years(?) because of the “unintended accelration” fiasco, and had to fight for their very lives to overcome that, now gives us unrealistic acceleration?

    Way to screw with your potential customers, guys.

  • avatar
    ttacgreg

    Something about your website is messing up Safari and Chrome (webkit browsers)get nearly paralyzed by some sort of script. This does not happen with Fire Fox or Camino (gecko browsers). This happens on all three Mac I have access to. Does not happen at work with IE6 thanks
    Additionally, the password verification in the “contact us” does not work either, thus this entry in the comments section on amy browser . . . . HELP!
    thanks

  • avatar
    carve

    My 335i automatic makes about 3,700 lb ft at the wheels in first from 2000-5000 rpm, making assumptions for driveline loss, but NOT considering torque amplification from the torque converter!  My 5-spd Jeep Cherokee 4.0, with much less power but a low-range transfer case, probably makes a LOT more, since it redlines at about 8 mph in 1-Low.
    However, by the time you get in 6th gear, the 335i is only making about 600 lb ft at the rear wheels.  If the E-tron is a one speed and can maintain that kind of wheel torque up to, say, 140 mph, then that is indeed impressive.  The figure is still misleading, but having 1st-gear-like wheel torque at over 100 mph would be unbelievable.  If the car has multiple forward gears, then the claim is pure BS.

    • 0 avatar
      Paul Niedermeyer

      It can’t.  All electric motors make max torque at zero rpm, or very close to it, and then it drops off as it revs up.

    • 0 avatar
      carve

      My curiosity got the better of me.  My 95 Cherokee has 220 lb ft of torque.  Assuming a 20% drive line loss, after the…
      2.72:1 transfer case low range
      3.83:1 first gear, and
      3.07:1 final drive, it makes…
      5,629 lb ft of torque at the wheels!  Wow- I guess Jeep doesn’t know how to advertise.
      Newer ones had 245 lb ft at the crank.  Combined with the 3.73:1 rear end available with the tow package, which unfortunately was only available in autos with 2.8:1 first gear, would make 5,568 lb ft at the wheels. A manual trans with the uprated engine would make 6,268 lb ft at the wheels- truly locomotive numbers…at the locomotive’s crank.

      Edited: Wikipedia says the 4.56:1 rear wasn’t available with a manual trans or with the 6-cyl. 3.07 is the lowest final drive in manual I6 Jeeps. A theoretical 2001 manual Jeep with 4.56:1 gears would make 9,310 lb ft assuming 20% driveline loss

    • 0 avatar
      carve

      I understand electric motors make max torque at 0 rpm and it falls from there.  However, the torque falls only because it’s overcoming more friction and, possibly, limitations in the circuitry at higher speeds.  I don’t imagine torque would fall very far.
      Their number is still BS though.  They should say “500 lb ft of torque with 2nd gear-like acceleration from 0-140 mph”.  Having a motor at each wheel, this is almost certainly a one-speed (could you imagine the mess of coordinating the shift at four wheels independently!?  Off by a milisecond and you’re in the ditch)

    • 0 avatar
      Eric Bryant

      @carve:

      Note that the torque potential is indeed max at zero RPM, as there is no back EMF (BEMF) and thus the maximum potential exists for creating current flow in the windings (at this operating point, the theoretical current is a simple matter of Ohm’s law – I=V/R).

      As the motor speed becomes non-zero, the BEMF increases proportional to the motor speed (as established by the speed-voltage constant of the motor multiplied by the rotational speed). The BEMF subtracts from the supply voltage, so the voltage available to create current flow decreases. In the speed-torque plot of a motor, this causes the characteristic negative slope.

      A somewhat-lesser effect on the torque loss is the inductance of the winding, as this causes a rise in the motor winding impedance. For motors with a large pole count, this can become quite considerable at higher speeds. If you look at the speed-torque of some motors, you may see that the slope isn’t just negative but also exhibits some second-order effects (the curve is concave) – that’s the effect of winding inductance. This is often neglected in back-of-the-envelope calculations or theoretical speed-torque curves, but shouldn’t be ignored until proven trivial.

      Finally, there is the current limit of the supply electronics (or “inverter”, depending on your terminology). This will “cap” the torque at a certain value, which appears as a flat spot on the far left side of the speed-torque curve. Depending on the motor and inverter characteristics, this may cause a considerably large region of operation in constant-torque mode.

      OK, lesson over. On to the snark – my modified ’96 GMC K2500 makes 9,900 lb-ft of torque at the wheels, and that ignores the probable ~2-2.5 STR of the torque converter. So is Audi impressed by this?

      If I ran the world, I’d abolish engine-only dyno plots and claims of peak power and torque. The only thing we would be allowed to discuss would be thrust plots, which do a nice job of wrapping up the engine, gearing, tire roll-out, and velocity  into something which is fairly meaningful (especially if related to vehicle weight). Longitudinal force at the contact patch is what matters – discussion of anything else is only part of the story.

  • avatar
    LastResort

    When I first read Audi’s claims three months ago on another site, I called bullshit as well.
    I’ll use a 05 WRX, because that’s what I have.

    3.454 first gear
    3.90 final drive
    217 ft lb of torque at 4000rpm

    3.45400 * 3.90 * 217 = 2923 ft-lb of torque in first gear.

  • avatar
    Steven02

    The 3k claim for torque… only requires 1.21 jigawatts of power.

  • avatar
    davejay

    Something about your website is messing up Safari and Chrome (webkit browsers)get nearly paralyzed by some sort of script. This does not happen with Fire Fox or Camino (gecko browsers). This happens on all three Mac I have access to. Does not happen at work with IE6 thanks
     
    I actually have seen this problem for about a week on my mac, on safari AND firefox. I’ve finally had to start visiting the site with flashblock running. My gut says its one of the ads being served to the site.

  • avatar

    Re torque: And frogs can fly. I’ve seen them, after a tornado, in the Midwest, cruising through the air. It’s quite amazing, really.

  • avatar
    Facebook User

    I think the relatively low 0-60 times is because they have geared the car so they can achieve a very high top speed, which is considered important to the germans to claim a car is truly a “supercar” since they actually drive that fast on a regular basis.
    If they geared the car to the tesla’s top speed of 120 or so I’m sure their 0-60 numbers would be pretty quick.


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