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Audi e-tron
Concept has four electric motors and a single battery pack

The world of electric and hybrid vehicles is progressing and growing at a rapid pace. While most people still think of hybrids and electric vehicles as low performance machines, there are an increasing number of high-performance electric vehicles being unveiled.

The first high performance EV was the Tesla Roadster with good performance thanks to the impressive torque of the electric motor. Audio has unveiled its latest concept car at the International Motor Show in Frankfurt called the Audi e-tron which just so happens to look like an electrified Audi R8.

The most impressive feature of the concept isn’t just its all-electric power train, but its tremendous amount of torque. Audi claims that the e-tron has a torque rating of  3,319.03 lb-ft. All that torque is generated by four individual electric motors situated at each wheel allowing the vehicle to be all-wheel drive.

The car has a total of 313 HP and promises to hit 60 mph in about 4.8 seconds. A more impressive number is that the car can go from about 37 mph to 74 mph in only 4.1 seconds. The all-electric range for the lithium-ion battery pack is 154 miles.

The EV is a large beast at 3,527 pounds and it measures in at 74.5-inches wide x 167.72-inches long and 48.43-inches tall with a wheelbase of 102.36-inches. The massive single battery pack alone weighs 1,036 pounds.

"We are trying to find a concept that requires no compromises," says Michael Dick, Member of the Board of Management of AUDI AG, Technical Development. "Electromobility means more to us than just electrifying conventional cars. Instead, we are dedicated to a holistic approach to all aspects of the topic."

Audi's American President called potential Volt buyers idiots not long ago and then quickly claimed he forgot what he said. There was only speculation surrounding the Audio EV concept at the time the comments were made.



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RE: <Drool>
By guacamojo on 9/15/2009 1:08:59 PM , Rating: 3
quote:
Where did you get that 5252 number from? And what are its units?


It's just a unit conversion.

Power = Torque * Angular Velocity

1 HP = 550 ft-lbf/sec
1 RPM = Pi/30 rad/sec

So Horsepower = Torque (ft-lb) * RPM * Constant

The units of the constant are HP/(ft-lb * RPM), or if you put the constant on the other side of the equation, (ft-lb)(RPM)/(HP)

The actual value is 550*30/Pi, or 5252.113 (ft-lb)(RPM)/(HP)

quote:
I can say that you do not calculate Electric motor numbers the same way as Internal Combustion motor numbers


Actually, you do. Physics = physics. But there's a flawed assumption in the OP's calculation. Peak power and peak torque do not necessarily coincide. Peak torque could be at stall, in which case RPM = zero, and horsepower = zero.

In fact, peak torque and peak horsepower rarely coincide. But that's an aside.


RE: <Drool>
By Sulphademus on 9/15/2009 2:14:46 PM , Rating: 2
quote:
Peak torque could be at stall, in which case RPM = zero, and horsepower = zero.
In fact, peak torque and peak horsepower rarely coincide. But that's an aside.


Every electric motor I have seen makes peak torque at 0rpm. I dont understand how you can have torque which, AFAIK, is motion if nothing is moving. (Well, aside from gravity) What kind of output does such a motor have when its not at 0? Like when its actually pushing the car?

5252rpm is where torque=horsepower, its the crossing point. Any rpm lower than that torque will be the greater number. Any rpm higher and HP will be the greater number. From all the dyno graphs Ive seen, this crossover tends to be at 70 to 80% torque.


RE: <Drool>
By guacamojo on 9/15/2009 4:20:49 PM , Rating: 2
quote:
Every electric motor I have seen makes peak torque at 0rpm.


Not if you've ever seen an AC motor (like on a fan, dishwasher, table saw...) AC motors have a resonant rotor, which optimizes their efficiency at speed, and reduces slippage (the difference between line frequency and synchronous motor speed.)

In an AC motor, the torque increases as you slow the rotor, up to a point called the "breakdown torque" which happens at a non-zero speed. If you reduce the speed still further, the motor torque will drop.

quote:
I dont understand how you can have torque which, AFAIK, is motion if nothing is moving.


Torque is just a rotary force. As such, no motion is required or implied. When you're standing on the cheater bar, trying to loosen the wheel nut on a VW Beetle, you're exerting a torque on the nut (equal to your weight times the length of the cheater bar), but one which isn't enough to unseat that damned nut. The nut isn't moving, but the torque is there.


RE: <Drool>
By HVAC on 9/15/2009 4:43:36 PM , Rating: 2
Electric motors that make peak torque at 0rpm are typically ones with permanent magnets inside (usually bonded or glued to the rotor). AC induction motors do not have permanent magnets, requiring oscillating electromagnetic fields to create or "induce" opposing magnetic forces in order to build up torque. Therefore, they do not have the same torque vs. speed curves.


RE: <Drool>
By Sulphademus on 9/15/2009 4:47:00 PM , Rating: 2
Yeah I've had that with lugnuts before.

Still though, torque without motion accomplishes nothing.
Example: http://www.caranddriver.com/reviews/car/09q2/2011_...
Torque (SAE net): 295 lb-ft @ 0 rpm

I know that they always publish peak numbers but if the rotary force that pushes the car forward is not rotating then its pointless as far as I am aware. The millisecond that the torque of the motor overcomes the gravity of the car, which is kinda the point, then we're no longer at 0 revs.
Maybe the torque curve is rather flat and no one's bothered to tell me?


RE: <Drool>
By guacamojo on 9/15/2009 6:32:47 PM , Rating: 2
quote:
Still though, torque without motion accomplishes nothing.


My point exactly. The peak torque of a prime mover is not the most important spec. The power output is.

Peak power, not peak torque, is what limits your 0-60 time (or more importantly, your 40-60 time.) It's what limits a car's speed, or sets how fast a truck can haul up a grade.

You can gear up or down to get more speed or torque, but no gearing in the world can give you more power than you started with.

You see it all the time in "sporty" economy cars. They have a short first gear to make the car feel peppy off the line, but they can't maintain acceleration because there's no power.

A little fractional horsepower winch can pull up a stump if you're patient and have enough gear reduction. But it won't push a golf cart up a hill at 5 mph.


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