• Dec 3rd 2009 at 9:27PM
  • 31
Audi e-tron concept - Click above for high-res image gallery

When introduced at the Frankfurt Motor Show in September, Audi boasted its all-electric e-tron was fitted with four electric motors producing "230 kW (313 horsepower) and 4,500 Nm (3,319.03 pound-feet) of torque." While the e-tron's styling may have raised a few eyebrows, we were notably moved by the quoted torque figure – especially when we considered that the twin-turbocharged Mercedes-Benz SL65 AMG, one of the most powerful vehicles on the road, makes 738 lb-ft in comparison. We were stupefied by the number, and it set off more than a few debates among our group, but Audi made no attempt to clarify...

The team at Automobile Magazine, initially duped like everyone else, has recognized that Audi was quoting torque measured at the wheels, not at the output shaft – the industry standard. Measuring torque at the wheels takes the multiplication effect of the transmission and final drive gears into account. The resulting figures are generally ten-fold of what they would be at the crank (meaning cars like a 3.6-liter Chevrolet Malibu packs a similar 3,115 lb-ft of torque). Audi's e-tron torque figures are not exactly dishonest, but they are using a completely different evaluation without making mention of it in the press release. Long story short, Automobile estimates the e-tron makes about 252 lb-ft of torque, or a bit less than the Tesla Roadster's 273 lb-ft.

[Source: Automobile]

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    • 1 Second Ago
      • 5 Years Ago
      Right, but since the e-tron uses four in-wheel electric motors, there's no transmission and hence measuring torque at the "output shaft" is the same as measuring it at the wheels.

      I'd have thought that was obvious, but I guess not.
        • 5 Years Ago
        there's the lever known as wheels, my main man.

        You're correct, but if a net force is applied on an object, it will move in the vector of the applied force.
        • 5 Years Ago
        Torque is a rotational force. How would you measure rotational force at 0 rpm?

        If the wheels are directly connected to the motors then the numbers should be accurate, however if there was a planetary gearset between the motor and wheel, then the torque would differ.
        • 5 Years Ago
        if you know anything about motor, you will know this 3319 lb-ft of torque is very likely measured at 0 rpm.
        translation: if you are not moving, why would you care how much torque it can produce?

        • 5 Years Ago
        Sergey, you don't measure torque on a dyno, because torque is phantom. You measure power output. So it doesn't matter how big the roadwheel is.

        And electric motors don't have level torque curves, they tilt downward. Basically, you put in X Watts of power and it turns into Y RPMs and Z torque. As the RPMs go up, the torque goes down as an inverse. The only way you could not have the torque drop as the RPM goes up would be to put in more power. And in general if you put in more power later, it means you were putting in less than you could have before. So at full bore, the torque curve should be somewhat close to a linear downward line.
        • 5 Years Ago
        • 5 Years Ago
        While the 3319 figure might be technically correct, it is meaningless to compare torque between electric and combustion driven cars. In the combustion engined car you get max wheel torque by multiplying engine torque by the 1st gear ratio and then by the final drive ratio.
        A Honda Fit makes 1619 lb-ft of torque at the wheels.
        It is also correct that an electric motor produces max torque at 0 rpm.
      • 5 Years Ago
      You know every VW guy are beating off to those wheels
      • 5 Years Ago
      10 points to Automobile Magazine & Autoblog for FINALLY picking up on this.

      I've written two blog posts and left about 10-15 comments trying to get editors to wake up to this instead of blindly repeating implausible torque figures without question.

      Admit it.... now that it's been explained, it's obvious, isn't it!!!

      To be honest, without knowing the reduction gear ratio, you can only guess at the motor torque. Automobile Mag had a punt at a 13.2:1 gear ratio but the Tesla Roadster runs only a 8.25:1 reduction gear. I'm guessing Automobile Mag don't know that!
        • 5 Years Ago
        Except it is wrong...if you do the math the torque figure is completely plausible.


        So if these motors are 313 HP in an ideal case they will make about 3289 lb ft at 500 RPM. As you can see by the equation torque goes up as RPM goes down, and there are certain physical limits that come into play as RPM approaches 0, but 3,319.03 lb ft is certainly a logical number. Why do you think Diesel electric locomotives use the electric motors? Buckets of torque.
        • 5 Years Ago
        Yeah, thanks for keeping up the good fight.

        This article reads much like the post I made in the last thread, although I did my math with a GM 3.6L DI LLT engine example, they used a 3.6L non-DI LY7. Theirs matches up slightly better, probably on weight too (a Malibu surely weighs less than a luxury wagon).

        I still think Audi is measuring at the shaft, it just has 4 shafts and no tranny. So each motor puts out about 850 ft-lbs peak.
      • 5 Years Ago
      The word 'comments' is plural, so you should have used 'are' instead of 'is.'

      If you're going to write something stupid, use proper grammar. :)
      • 5 Years Ago
      Well, you just fell in your own trap now didn't you? You posted after your own comment. You know what that means... Hello!
      • 5 Years Ago
      deceptive and the car just looks odd.
      • 5 Years Ago
      there is no normal transmission involved, each motor is connected directly to the wheel, so it makes sense to measure the torque like they did.
      • 5 Years Ago
      Too bad they're gonna water down the production version. I was super excited for the A8 and it is very bland.
      • 5 Years Ago
      It's still deceptive.

      Shame one you Audi
      • 5 Years Ago
      That Audi, so hot right now.
        • 5 Years Ago
        I will wait till we get a behind the wheel impress to make a judgment call on this car. Although I still think the R8 looks and sounds better.
        • 5 Years Ago
        sorry, gotta disagree.

        To me it looks like they took the most attractive Audi ever and beat it with an ugly stick before crapping on it.
      • 5 Years Ago
      I'm sure they look much better in person but the monochrome style makes them look rather bland, like giant pop sickles.
      • 5 Years Ago
      Well if theres 4 motors, one in each wheel, then wouldn't it make sense to measure the torque from the wheels? The way i understand it is theres no traditional central engine so one can't really compare these numbers to that of a traditional car. This is much the same in the case of the Chevy Volt and their 230 mpg rating is it not?
        • 5 Years Ago
        According to Audi, "The two electric motors, which have their own cooling system, are mounted behind the rear axle. The front electric motors are mounted on the front axle, with their cooling system arranged in front of them."

        It doesn't sound like each motor is mounted on its own wheel.

        - Mike
        • 5 Years Ago

        On the current EPA testing cycle, the Volt would not consume any gasoline at all in the individual tests. The numbers for the Volt are bogus, but at least Chevrolet tried to follow what they thought the EPA was going to put forth as a mileage test.

        It's a little different for Audi, since they can actually get back (mathematically), to an equivalent value for an ICE vehicle. In either case, it's still marketing.

        Just like Chevrolet won't be quick to tell you what EPA rating the Volt gets when only running on the range extender, I don't really think Audi will be publishing a torque curve showing motor torque at ~1650RPM, where the car would be going about 120mph (assuming there's no gearing on the motors).
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