Audi Introduces Second e-tron Electric Sportscar Concept at Detroit Show
12 January 2010
| Audi e-tron Detroit Showcar. Click to enlarge. |
Audi introduced a new electric sportscar concept at the North American International Auto Show, its second following the introduction of the initial e-tron at the 2009 Frankfurt Motor Show in September. (Earlier post.)
The Detroit showcar Audi e-tron is a 3.93 meter (155 in) long, 1.78 meter (70 in) wide and 1.22 meter (48 in) tall two-seater, with a gross weight of around 1,350 kilograms (2,976 lbs)—smaller than the first e-tron. Two electric motors with a combined output of 150 kW (204 hp) and 2,650 N·m (1,956 lb-ft) accelerate the coupe with its Audi Space Frame-design aluminum body from 0 to 100 km/h in 5.9 seconds.
This e-tron accelerates from 60 to 120 km/h (37 - 75 mph) in 5.1 seconds. The top speed is limited to 200 km/h (124 mph).
The two motors, which have their own cooling system, are mounted on the rear axle. The Detroit showcar Audi e-tron is able to distribute its electric motors’ high torque between the wheels entirely as required.
The torque vectoring is the key to a high level of active precision and excellent traction. Thanks also to its low weight, short wheelbase and perfect weight distribution for dynamic handling, the Audi e-tron has the drivability of a go-kart, according to the company—agile, good on bends and neutral right up to the very high handling limit.
A 45 kWh 399 kg (880 lbs) Li-ion battery pack is located for an optimal center of gravity behind the passenger compartment and ahead of the rear axle, along with the converter and power electronics. The car has a potential operating range of up to 250 kilometers (155 miles) on the NECD.
This special package, featuring a 40:60 weight distribution, ensures perfect balance, which contributes to the driving dynamics of the Audi e-tron.
The energy storage unit is charged with household current (230 volts, 16 amperes) via a cable and a plug; the socket is behind a cover at the back of the car. The charging time when the battery is empty is around 11 hours, but a rapid charge (400 volts, 32 amperes) cuts this to around just two hours.
| Audi e-tron Concepts | ||||||
|---|---|---|---|---|---|---|
| Frankfurt | Detroit | |||||
| Dimensions l x w x h (m) | 4.26 x 1.9 x 1.23 | 3.93 x 1.78 x 1.22 meter | ||||
| Drive / motors | All-wheel / 4 | Rear-wheel / 2 | ||||
| Power | 230 kW (313 hp) | 150 kW (204 hp) | ||||
| Torque | 4,500 N·m (3,319 lb-ft) | 2,650 N·m (1,956 lb-ft) | ||||
| Battery pack capacity | 53 kWh | 45 kWh | ||||
| Pack weight | 470 kg (1,036 lb) | 399 kg (880 lbs) | ||||
| Range | 248 kilometers (154 miles) | 250 kilometers (155 miles) | ||||
The Detroit showcar Audi e-tron in its further developed version features an electro-mechanical brake system that enables further exploitation of the potential of electric motors for energy recovery. A hydraulic fixed-caliper brake is mounted on the front axle, with two novel, electrically actuated floating-caliper brakes mounted on the rear axle. These floating calipers are actuated not by any mechanical or hydraulic transfer elements, but rather by wire (“brake by wire”). In addition, this eliminates frictional losses due to residual slip when the brakes are not being applied.
One design element that is specific to electric vehicles developed by Audi—such as the Audi e-tron—are the air intakes in the single-frame grille and behind the side windows on the C-post. They are closed flush under normal circumstances and opened by retracting slats when additional cooling air is required. The slats above the drive unit then also open to provide a better through-flow of air. These measures, too, maximize efficiency—the concept car is outstanding for an already low drag coefficient that is further improved when the flaps are closed.
The ASF body. The body structure is based on Audi Space Frame technology (ASF), with a hybrid design approach adopted. All add-on parts—doors, lids, sidewalls and roof—are made of a fiber-reinforced plastic.
The combination of aluminum and carbon fiber-reinforced composite material guarantees supreme rigidity coupled with low weight. Audi will soon use this technology in a similar form for future production vehicles. Despite the complex drive system layout with two electric motors and a high-capacity battery system, the total weight of the Audi e-tron showcar on display in Detroit is only around 1,350 kilograms.
Heat pump. The heat pump that made its first appearance on the Audi e-tron concept car shown in Frankfurt also helps to boost efficiency and range in the Detroit car. Unlike a combustion engine, the electric drive system generally does not produce enough waste heat to effectively heat the interior. Other electric vehicles are equipped with electric supplemental heaters, which consume a relatively large amount of energy. The heat pump used by Audi is a highly efficient machine that uses mechanical work to provide heat with a minimum input of energy.
A high-efficiency climate control system is used to cool the interior. It works together with the thermal management system to also control the temperature of the high-voltage battery.
As soon as the vehicle is connected to a charging station the vehicle is preconditioned as appropriate by the thermal management and other associated systems. In cold conditions the drive system is preheated, and in hot conditions it is cooled. This preconditioning can also be extended to the interior, if necessary, so that the passengers can step into a cabin that has been heated or cooled as appropriate for their comfort.
Some progress but not nearly enough to compete with the performance of Tesla’s Roadster.
Tesla: 0 to 60 in 3.9 sec and 244 miles range. Weight 1235 kg. Tesla sport ed 0 to 60 in 3.7 sec.
Audi: 0 to 60 in 5.1 sec and 150 miles range. Weight 1350 kg.
So what does Audi do wrong?
1) Audi uses two electric motors. This is a bad idea as larger electric motors are more efficient and has a higher power to weight ratios than smaller electric motors. Note that the opposite is typically the case with combustion engines.
2) Audi may use less carbon fiber than Tesla does.
3) Audi probably still has far less efficient power electronics and other electric subsystems (electric braking, electric servo steering, electric AC) than Tesla.
I can’t help to think that Tesla has done a hell of good job with their first EV and I am sure they will also beat the competition by several years with their next Model S.
Posted by: Account Deleted | 12 January 2010 at 03:59 AM
It would be helpful if the reported Wh/mile.
Not knowing DoD, we might assume 70%, which would give 53 x 0.7 = 37kWh
Then 37000Wh/153m = 241 Wh/m
That would about equal the Tesla at a steady 55mph.
http://www.teslamotors.com/blog4/?p=70
The Rav4 averaged about 400 Wh/m.
http://www.evchargernews.com/miscfiles/sce-rav4ev-100k.pdf
The GM EV-1 achieved 179 Wh/m, which sets a standard that automaker should shoot to beat.
http://web.mit.edu/evt/summary_mpgge.pdf
Posted by: Will S | 12 January 2010 at 06:14 AM
Henrik,
There is much more to performance than straight lines. Let's wait until Audi actually produces this sub-TT sized e-tron and then put them both on the track. Two motors gives special advantages that not even the most advanced rally-inspired electric differentials can match (if the control software is up to snuff).
The Lotus Elise chassis (in the Tesla) is great for handling - in its original 1750lb form. Not sure how it performs as a ~2700lb vehicle.
Posted by: Patrick | 12 January 2010 at 09:30 AM
"Space Frame technology"
This is the idea that was used on the Pontiac Fiero and some Saturn models. It keeps the weight down and strength up. If you are going to create an EV weight is a major factor. This sounds like a great car, but price will be a consideration.
There are people in southern California that buy small luxury cars for commuting. They put on 100,000 miles in 5 years and sell them with steep depreciation. If they could go more than 100 miles per day and charge at home, the savings in fuel costs could offset at least some of the depreciation.
Posted by: SJC | 12 January 2010 at 09:50 AM
I posted last year that a shared axis motor pair as described would eliminate the differential and offer another traction control point. On a single alxe vehicle, 0 turn radius is possible.
Thee may be benefits in lower power control unit even though duplication be necessary, the cost and reliability could be a positive.
The comments went on to the pros and cons of wheel motors as I recall.
Although this is a concept so in cyberspace still, I applaud this approach .
Posted by: arnold | 12 January 2010 at 04:59 PM
Henrik,
I don't get your point about the two electric motors being silly. On the contrary, it is smart. You can ditch the differential, save space, lower weight, reduce the number of mechanical components and have infinitely more control over how much power goes to which wheel.
Secondly, you can't compare two automobiles on specs alone. The Audi could cost 50 grand less. Who knows....
Posted by: Arne | 13 January 2010 at 02:57 AM
Anne
The conventional R8 starts at 114000 USD (1) so I would expect that the e-tron version to be more expensive as it will need an expensive battery.
You have a good point about saving weight from eliminating the differential when using two electric motors instead of one. However, I will insist that you still save more weight all in all by using one electric motor, one motor controller and one cooling system instead of two of each. It will also save production cost as you will need fewer parts.
Others have tried to use several EV motors but then eventually changed it to one central motor. Remember Mitsubishi started with 4 in-wheal motors for the iMiEV but ended up will one central in the final version. (2) I expect Audi to do the same with the e-tron eventually. I can only find one strong reason to prefer the e-tron over the roadster and that is design.
1) http://www.audiusa.com/us/brand/en/models/r8.html
2) http://www.greencarcongress.com/2006/10/mitsubishi_acce.html
Posted by: Account Deleted | 13 January 2010 at 04:06 AM
Henrik,
Two motors = more surface area for cooling so the cooling demands may not be as great.
Also note that this is based on something more akin to the TT and not the R8. This is a different E-tron from the R8 version and I would think the price differential between an R8 and a high-level TT could also apply here as well.
Posted by: Patrick | 13 January 2010 at 09:45 AM
Patrick
According to Wikipedia and other news reports the e-tron is based on the R8 so this is why I compare it to the price of the R8.
See http://en.wikipedia.org/wiki/Audi_R8#Audi_e-Tron
Posted by: Account Deleted | 13 January 2010 at 11:39 AM
Audi took a great concept and gutted it.
The original e-tron was a Quattro Drive with a motor for each wheel and much better performance numbers than these. Not as good as the Roadster, but good enough to compete. Plus the R8 looks WAY better than the Lotus Elise.
I hope Audi guts the estimated $160,000 price tag to go with all of these downgrades. Lame as hell.
Posted by: Aaron Turpen | 13 January 2010 at 08:24 PM
Henrik,
The wikipedia article you cite discusses the 2009 e-tron concept at the Frankfurt auto show.
This is a different e-tron concept built on a much smaller platform for the Detroit North American International Auto Show. Apparently it is the platform to be used for the R4.
http://green.autoblog.com/2010/01/13/detroit-2009-audi-e-tron-detroit-concept-presages-production-r4/
"we're anticipating that the Audi R4 will slot in under the TT in the low-$30,000 range, as the 2010 TT presently starts at $37,800."
http://www.audisite.com/1042/audi-r4-a-mini-r8-electric-roadster/
Posted by: Patrick | 14 January 2010 at 08:22 AM
Two motors (one for left wheel, one for right), without differential is superior in theory but some practical issues may outweigh benefits, as Henrik pointed out.
Other than reasons already mentioned, there are probably concerns regarding asymetry between motors and belonging power drives that may develop over time for whatever reasons. And it's almost impossible to develop control software that will compensate for something/anything of unknown origin. What if one motor or its driver starts underperforming, and existing sensors cannot detect it?
Another thing that a car with left and right motors has to have is a supervisory system that monitors symetry of the two systems, requiring extra sensors and complexity.
Tesla Roadster doesn't have limited slip differential, and nobody complained about it. Probably they solved it using cleverly ABS elements, like in the new VW Golf GTI where torque steer was eliminated that way. The price is somewhat more brake wear, but those who drive hard wear them anyway.
Posted by: MG | 14 January 2010 at 08:59 AM
Patric the only thing that changed from Frankfurt to Detroit in terms of design was the color from one in read to one in metallic gray and another in orange.
Audi’s design is a huge plus in my humble opinion. The Roadster does not look too great with the hood on and it has too many broken lines and curves to my taste. Audi should buy a couple of Tesla's roadsters and study how they did the powertrain and then do something similar without braking any patens of cause. I believe Porsche is doing exactly that right now but they don’t talk too much about it.
Posted by: Account Deleted | 14 January 2010 at 11:19 AM
Here is a link to Porche researching Tesla.
http://www.themotorreport.com.au/13444/porsche-buys-tesla-roadster-for-research-purposes/
Posted by: Account Deleted | 14 January 2010 at 12:53 PM
"Patric the only thing that changed from Frankfurt to Detroit in terms of design was the color from one in read to one in metallic gray and another in orange."
Absolutely wrong. Did you bother to read any of the links I posted? Obviously not. Did you bother to even do the slightest modicum of research? Obviously not.
There is even a gosh-darn link in this article to the first incarnation of the e-tron at Frankfurt! Did you bother to read the TABLE describing the two incarnations of the E-tron?
Please, go do the research before you respond again with respect to the two DIFFERENT versions of the E-tron presented at Frankfurt and Detroit.
Sorry to be rude, but I completely taken aback by your misinformed statement and adamant stance when the evidence refuting your claim is so plainly displayed and easily researched at multiple resources.
Posted by: Patrick | 14 January 2010 at 01:24 PM
Patrick I am sorry I apology. There are more design changes than the color. I didn’t notice at first and yes I only spend a few seconds looking at the pictures linked below. To be sure, by design I mean visual exterior design not power train design which I am fully aver has changed quite a lot. I still do not see enough visual design changes in the pictures below to believe they have changed the platform the e-tron is based on. We will see what the price is when it comes out. I have already speculated too much about that.
Frankfurt
http://bioage.typepad.com/.a/6a00d8341c4fbe53ef0120a5c78e98970c-popup
Detroit
http://bioage.typepad.com/.a/6a00d8341c4fbe53ef012876c8a746970c-popup
Posted by: Account Deleted | 14 January 2010 at 02:32 PM
Yes, I had not even considered the sheet metal design. I was only talking about powertrain (number of motors, battery size) and the dimensions (0.33 x 0.12 x 0.1 meters smaller in length x width x height).
If you were only looking at the sheet metal, I now understand why you stated there were no design changes.
From what I understood of what I read, the first incarnation was taken directly from the R8 and the second is taken from the "speculated" R4.
Posted by: Patrick | 14 January 2010 at 04:51 PM
Henrik,
The platform has changed too: the Detroit e-tron is 33 cm shorter and 12 cm narrower than the Frankfurt version. A much smaller car.
Posted by: Arne | 15 January 2010 at 03:23 AM
Anne and Patrick
As I get it both the Frankfurt and the Detroit e-trons are based on a shorter version of the R8 platform that they will call the R4 platform when it go on sale sometime in 2012 both in a gas version and an EV version. See 1 and 2. If you study the pictures of the Frankfurt and the Detroit versions closely they look very much alike so I do not think there are important platform changes from Frankfurt to Detroit. I expect to see the same level of luxury in the R4 as in the R8 with regard to interior design. I don’t see anything that convinces me it is based on the much cheaper TT platform. Autoblock’s price speculation is just that as the battery alone will cost about 30000 USD (low volume production Tesla type to be able to get the needed energy density). But then again I may be wrong.
1) http://en.wikipedia.org/wiki/Audi_e-Tron
2) http://www.gizmag.com/audi-e-tron-detroit-concept-ev/13840/
Gizmag say the Detroit e-tron is 22 centimeters shorter at the wheelbase than the R8 platform.
Posted by: Account Deleted | 15 January 2010 at 04:45 AM
I think their (autoblog) price speculation was solely on an ICE powered R4.
What Gizmag said with respect to the wheelbase for the Frankfurt version:
http://www.gizmag.com/the-audi-e-tron-electric-quattro-with-4500-nm-of-torque/12836/
2.6m wheelbase
It seems the R4 platform was in flux or perhaps it was not ready at Frankfurt when they wanted to show the E-tron.
Posted by: Patrick | 15 January 2010 at 11:16 AM