There was a time when people can’t seem to contain themselves when talking about Audi’s e-Tron Concept. But now that its claim to have 3319 lb-ft of torque has been explored, the enthusiasm for the concept, which is currently on display at the 2009 L.A. Motor Show, has waned quite a bit. At the recently held Frankfurt Auto Show, the electric sports car was applauded for its 3319 lb-ft of torque, which is roughly ten times what most other cars have.
Now that the e-Tron makes its North American debut in L.A., the excitement has been lessened somewhat due to the discovery that the E-tron’s real torque output is much closer to 300 lb-ft than 3000 lb-ft. Audi wasn’t exactly lying; it was that it had used a different way of measuring torque. Audi measures the e-Tron’s 3319 lb-ft of torque at the wheels while other firms report peak torque at the output shaft of a motor or engine.
The difference between torque at the wheels and at the powerplant is typically about ten-fold due to the torque multiplication effect of transmission and final drive gears. Having said that, Audi hasn’t revealed how much torque the e-Tron actually produces from its four electric motors. The E-tron has 19-inch wheels wrapped in 235/35 rubber. The car is believed to have a top speed of 125 mph.
Assuming that top speed is at the motors’ redline of 14,000 rpm, this would make it similar to the electric motor in the Tesla Roadster. From this, we can compare the rotational speed of the tires to that of the engine and then the gear ratio can be estimated. With a ratio of 13.2:1 for the e-Tron, the result is a total torque output at the motors of 252 lb-ft.
This is still very impressive but far from the 3319 lb-ft boasted by the company. If you compare the E-tron to a Tesla Roadster that makes 273 lb-ft of torque with a V-8 R8 that produces 317 lb-ft, it really remains to be an awesome piece of work. An electric sports car that does 0-62 mph in 4.8 seconds is quite an achievement. And it disappoints no one that the e-Tron is headed for production.