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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 MrBlastman on 9/15/2009 12:10:48 PM , Rating: 1
What is more amusing (I got this equation from my brother who is a car mechanic), is this torque figure is at an absurdly low RPM--495.29 RPM to be exact.

You can calculate it yourself:

313 HP * 5252 / 3319 = 495.29.

So, the torque might help it get off the line but the thing is a porker at 3527 lbs and with only 313 HP it explains why the 0-60 time is so mediocre with all that torque (that and it is very low end torque).

The thing that bothers me the most though is the independent electric motors, one for each wheel. That REALLY bothers me. If you are say going for a mountain run, or on the track and are in a tight turn (say a sharp one or a set of esses) and one of your motors happens to burn out due to the stress induced from the load on one of the wheels... You are going to go right off the side of the cliff or off the track into the wall (or another car).

Thanks Audi for the idea, I think I'm going to pass on this concept for now. Granted it gives higher efficiency due to being afforded no driveshaft, but, I'd rather take a traditional driveshaft/multi-differential design any day to give me more safety rather than taking that sort of risk. Sure, the odds might be low, but, I'm essentially doubling my risk for that type of catastrophe (as the risk already exists for a tire blowout). With a single engine the car would coast to a stop (though the weight bias would be changed depending on the acceleration which might cause a spin-out), I suppose though it depends. The risk is less however since there is one engine rather than four plus the individual wheel strain would be somewhat mitigated.


RE: <Drool>
By ice456789 on 9/15/2009 12:16:38 PM , Rating: 3
This may be a stupid question, but does RPM apply on an electric car the same way it does on a normal car?


RE: <Drool>
By threepac3 on 9/15/2009 12:50:10 PM , Rating: 2
They still do but aren't exactly relative to internal combustion engines.


RE: <Drool>
By Spuke on 9/15/2009 1:30:42 PM , Rating: 2
quote:
They still do but aren't exactly relative to internal combustion engines.
RPM is RPM. Electric motors don't have some special RPM. Electric motors spin, combustion engines spin.


RE: <Drool>
By JediJeb on 9/15/2009 2:54:16 PM , Rating: 3
quote:
RPM is RPM. Electric motors don't have some special RPM. Electric motors spin, combustion engines spin.


True, but there is gear reduction with regular drivetrains, but if the electric motor were coupled directly to the wheel with no gear reduction then they would spin over 3x slower than the IC engine would to produce the same speed. So if you are turning 1800rpm with an IC engine in your car now and you have enough torque to do a direct drive set up with the electric motor then it only needs to turn at 600rpm to make the same speed, and many cars only turn 1800-2200rpm at 60mph.

Another thing to consider is this is using 4 motors, if the torque is total then divide by 4 and you get the torque at each wheel. With all wheel drive it takes more torque to break traction since you have less to push against than when you have two wheels just sitting there holding you back somewhat.


RE: <Drool>
By Spuke on 9/15/2009 3:24:32 PM , Rating: 2
quote:
Another thing to consider is this is using 4 motors, if the torque is total then divide by 4 and you get the torque at each wheel.
Ah, you are right. Didn't think of it that way.


RE: <Drool>
By waykizool on 9/15/2009 1:44:34 PM , Rating: 2
No. Electric motors have max toque for the amount of current that is being applied, when it is applied. IC's always have toque as well, but it is not max until it hits the RPM range that is tuned to make max toque.


RE: <Drool>
By scrapsma54 on 9/15/2009 12:23:04 PM , Rating: 1
Sure audi may not have come up with it, but having an electric system has so much more potential to reduce fatal accidents. Think less sensors, less mechanical parts.
There is room for way better timings than on a mechanical system, and easier management of each motor.
I may not be an expert on electric vehicles, but who is right now?


RE: <Drool>
By jlips6 on 9/15/2009 12:43:33 PM , Rating: 2
http://endless-sphere.com/forums/

The guys on these forums are amazing. I highly reccomend visiting, even if you don't post. A great place to educate yourself about the practical application of electrical motors.


RE: <Drool>
By Spuke on 9/15/2009 1:32:11 PM , Rating: 2
quote:
http://endless-sphere.com/forums/
Is this a technical forum or some social/political forum?


RE: <Drool>
By jlips6 on 9/15/2009 4:35:08 PM , Rating: 2
I would say it's about 80% technical. they have special forums for off topic stuff (like politics) that I don't go to. Just stick to whatever topic it is you want to learn about (provided it has to do with electrical technology). Just visit the website, the homepage has a list of forum topics. Fantastic people there.


RE: <Drool>
By Spuke on 9/16/2009 11:42:35 AM , Rating: 2
quote:
I would say it's about 80% technical. they have special forums for off topic stuff (like politics) that I don't go to.
Thanks much, I'll check it out.


RE: <Drool>
By foolsgambit11 on 9/15/2009 12:28:00 PM , Rating: 2
It's pretty trivial to program the complimentary motor to stop if one fails - i.e., if the passenger side front died, the driver's side front could turn off as well, yielding a RWD car instead of AWD. Or a FWD, if one of the rear motors died. And you gain redundancy because of it. Instead of only one motor/engine dying to leave you stranded, it would take two.


RE: <Drool>
By scrapsma54 on 9/15/2009 12:34:41 PM , Rating: 2
But on only that, but adjust power to the outside tires around curbs.
Lets not forget regen braking on all 4 motors, either.
All the ideas on this independent drive train, just driving me nuts


RE: <Drool>
By MrBlastman on 9/15/2009 12:37:36 PM , Rating: 2
Limited slip differentials already do this mechanically. I suppose you could tie a sensor to have the wheel motors go out in pairs but it still bothers me that the odds of a single motor failing is quadrupled though the odds of total failure are halved (to be fair--assuming you need two motors to propel a set of wheels).

Either way, it sounds awfully expensive to me in terms of maintenance and repair costs. For the time being I'm going to continue to stay away from anything that is VW/Audi. They just tend to over-complicate things.


RE: <Drool>
By scrapsma54 on 9/15/2009 1:47:40 PM , Rating: 2
The limited slip differential does its job to the best it could do, but as software gets better and better, I can only see that having an independent motor system (if they are independent) can only be safer since on the fly failure detection is possibility.
If it isn't independent drive train, then failure of one motor isn't so bad, but I would imagine all that uneven torque would twist the body.


RE: <Drool>
By MrBlastman on 9/15/2009 1:58:46 PM , Rating: 2
Sure, the technology could be nifty indeed. I'd rather the car manufacturers stick to KISS (Keep it Stupid Simple) though if at all possible--doing so reduces potential time in the shop for repairs and maintenance.

Remember, just because it is electrical rather than mechanical does not make it less prone to faults. I remember our families 82 Cadillac Seville (leave out American car jokes), it was cutting edge with all the latest electronic gadgets and gizmos. The thing was always breaking down, and about 80% of the time it was due to electrical related malfunctions.

The more complex you make something, the more prone it is to being problematic. Sometimes a simple but practical design is better than a complex and elegant one.

In this car's case, it isn't twisting the body that is the problem if one engine were to fail, it is what happens to the weight distribution due to the uneven power output. If you're in a tight turn pushing the limits, any unintended change in weight bias to the traction can lead to potentially awful results. This is why autocross/track racing is so fun and exciting at the same time. There's a lot more to it than just turning your wheel and stepping on the gas. Throttle control is equally as critical as when you turn or brake.


RE: <Drool>
By rcc on 9/15/2009 2:23:57 PM , Rating: 2
If you're running a standard IC powered car and you get into the same situation, pressing hard in the turns, and your engine sputters or dies at the wrong time, you are in the same boat, or ditch.


RE: <Drool>
By Mr Perfect on 9/15/2009 2:35:25 PM , Rating: 2
Electric drive might make that bit more complex, but I bet the rest of the car's systems will get a lot simpler. There probably won't be an alternator/starter, fuel pump, separate brake system, transmission(?), driveshaft and maybe even no radiator/cooling loop.

It's not that ICEs are simple, they're just routine. :)


RE: <Drool>
By Spuke on 9/15/2009 3:39:08 PM , Rating: 2
quote:
There probably won't be an alternator/starter, fuel pump, separate brake system, transmission(?), driveshaft and maybe even no radiator/cooling loop.
LOL! Yeah those parts are SOOOOO complex. Sorry but the simplest thing in an electric car will be the motors themselves. Everything else will require a EE degree.


RE: <Drool>
By TomZ on 9/15/2009 4:49:31 PM , Rating: 3
The motors are also pretty sophisticated - probably also requires an EE degree to understand as well.


RE: <Drool>
By Spuke on 9/17/2009 1:45:04 PM , Rating: 2
quote:
The motors are also pretty sophisticated
What's sophisticated about a bunch of wires?


RE: <Drool>
By scrapsma54 on 9/15/2009 8:51:07 PM , Rating: 2
Well, I think the cooling part might be necessary, It does take a lot more to burn, but once those cells start boiling the whole car is going to be melted into the cracks on the road even if you extinguish the flames or not, lithium can self ignite in water.


RE: <Drool>
By Titanius on 9/15/2009 12:29:47 PM , Rating: 3
One question:

Where did you get that 5252 number from? And what are its units?

And from an engineering perspective, I can say that you do not calculate Electric motor numbers the same way as Internal Combustion motor numbers, they are just two completely different machines. So that is why I am curious to know what the 5252 number stands for.


RE: <Drool>
By MrBlastman on 9/15/2009 12:32:43 PM , Rating: 2
I really don't know; I read the article and called my brother up to talk briefly about the car and he mentioned that number to me and I used it to reverse equate it.

Though, I just did a search and here's a neat little article explaining 5252:

http://www.revsearch.com/dynamometer/torque_vs_hor...

I didn't really question him on it, he knows his stuff so I went out on a limb with my post.


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.


RE: <Drool>
By tastyratz on 9/15/2009 1:23:33 PM , Rating: 2
curve is totally different. Electric engines aren't like a gas engine when it comes to powerband - you have to think differently.
Besides, whether it happens around 500rpm or 5000rpm, who said you cant gear appropriately?


RE: <Drool>
By Spuke on 9/15/2009 1:36:03 PM , Rating: 2
quote:
curve is totally different. Electric engines aren't like a gas engine when it comes to powerband - you have to think differently.
There's no different thinking required. The electric motors hp/torque curve is different but not so complex that it requires a change in thought process.


RE: <Drool>
By mead drinker on 9/18/2009 10:10:27 AM , Rating: 2
This is perhaps the most short sighted thing I have seen posted in this discussion. First off the car has to, by nature of design, employ some sort of dynamic stability control where each wheel's revolution is monitored so that when taking a turn the outiside wheel's rpm is great than the insides as a result of to turning radius. With out such a system the car would be wheel hopping when taking every turn, think locked differential. Now, such systems employ their "stability control" by dynamically transferring load to the wheel with traction. In such cases where anomolies are detected the system removes load and goes into a coast. I would think that the failure of an electric motor would be considered such an anomoly. Remember there are no moving parts to this "drivetrain" and load is simply removed by not providing current to the electric motor. I am pretty sure that with the current DSC systems employed today by the Fiat brand of cars, and those that fall under VW, who have designed systems that calculate some thosands of time per second that this "catostrophic" scenario would have evaded them. Simply put: If one motor fails, then the one opposite is disengaged rendering the drivetrain either RWD or FWD in a limp home mode. Wow that was complicated!


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