VIDEO: Aerodynamics adds 7 miles to Volt electric range
Back in the spring of 2008 when General Motors took us on a tour of its wind tunnel facility, chief engineer Frank Weber emphasized the importance of aerodynamics in maximizing the electric driving range of the Volt. At that time, all we got see was a one-third scale model covered in various colors of duct tape. However, GM's aerodynamicists, including Nina Tortosa, explained that even at lower speeds, resistance to air-flow played an even bigger part in efficiency than the car's mass.
In the latest in a series of videos on the Volt development program, Tortosa describes the evolution of the Volt's shape as it has made its way to production form. Rather than a model, she uses a smoke wand to show the air-flow over one of the pre-production IVER vehicles. From concept to production, the Volt picked up seven miles of electric driving range just from changing the shape of the body. The rear, where the air-flow separates from the body, is one of the most critical areas and has to be carefully shaped to avoid uncontrolled turbulence. The final Volt shape came in second only to the tear-drop shaped EV1 (cD 0.195) in drag coefficient but with a more conventional four door body.
[Source: General Motors]
Reader Comments (Page 1 of 2)
David Martin 8:54AM (9/08/2009)
'However, GM's aerodynamicists, including Nina Tortosa, explained that even at lower speeds, resistance to air-flow played an even bigger part in efficiency than the car's mass.'
Surely this should read that at higher speed air resistance will play a bigger part, not at lower speeds, although regen braking means that many of the disadvantages of high mas are mitigated.
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Dave 9:05AM (9/08/2009)
Dont dent your Volt ... you'll lose 10 miles of range.
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Ghen 10:39AM (9/08/2009)
same for any car.
GoodCheer 9:10AM (9/08/2009)
Thing one: I do not believe that having a 4-door body is in any way an encumbrance in the design of a low cD form. (I'd also love to know the actual number, rather than just that it is the 2nd best GM design).
Thing two: Is this article complete without a this?
http://green.autoblog.com/2007/11/14/lutz-chevy-volt-aero-might-have-been-better-if-we-put-it-in-the/
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wincros 11:15AM (9/08/2009)
"Thing one: I do not believe that having a 4-door body is in any way an encumbrance in the design of a low cD form. (I'd also love to know the actual number, rather than just that it is the 2nd best GM design)."
You are completely correct. They are using good ol' marketing doublespeak. What they mean is not "four doors", but a notch back sedan. What they have done is sacrifice aerodynamics to the traditional American preference for a trunk sticking out the back. I suppose the low drag coefficient Kamm back is too new and revolutionary for GM or they really are afraid that people will say their $40K hybrid looks just like a Prius.
matthijs 9:39AM (9/08/2009)
Yeez nice antenna on the roof there. ;-)
With this in mind take a look at the Aptera and see how a vehicle that is really designed from the ground up to be aerodynamic looks like. (Beautiful isn't it?) A Cd of 0.15 But more important a low frontal area with resulted in a low drag area of 2.11 vs 3.95 for the EV1, (2004 Prius 6.24) The so called CdA figure. Look it up here: http://en.wikipedia.org/wiki/Automobile_drag_coefficient
Only stating a Cd number says nothing. If you make the Volt 2 times as big the Cd will still be the same but because of the bigger frontal area the CdA figure will look a lot worse. I would really like to know the CdA figure of the Volt.
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ziv 10:27AM (9/14/2009)
Matt, you are right about the cDa being the real number to watch. I think the Volt looks good, but thecDa will be the number which will tell us a good deal about how fast we will be able to drive on the interstate without butchering our AER. Aero will be crucial because it will be years, possibly decades, before we can get a light, inexpensive, long lived battery. I am hoping for the best, but any company as top heavy with MBA's as GM is, will probably not allow the engineers the free rein they need to do truly inspired work.
why not the LS2LS7? 11:41AM (9/08/2009)
Personally, I don't find the Aptera pleasing to look at.
Additionally, it's a joke as a car. GM has to compromise aerodynamic efficiency in order to make a vehicle that is practical as a car and good looking enough that people will buy it.
Look at what happened with the Insight, it eventually abandoned the trapezoidal shape, losing a little efficiency but gaining some customer appeal. The addition of two rear seats and an actual trunk also adds piles of value for most customers.
Bill 4:44PM (9/08/2009)
The Aptera remains a 2 seat enclosed cockpit motorcycle (not a car) which will likely require helmets and possibly a motorcycle endorsement outside of California.
And we're still waiting for actual (not computer simulated) crash tests for the Aptera, which the company said it would do last summer, but haven't yet.
Oh4Sh0 10:55AM (9/08/2009)
A saab bonnett, woo.
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ufgrat 8:20PM (9/08/2009)
Thanks to the EU pedestrian safety regulations, yes. Now, as long as they don't go sticking vital parts of the car inside the fenders...
paulwesterberg 10:39AM (9/08/2009)
Aerodynamics have always been the key to efficiency, why doesn't GM take this into account from the beginning when they are designing a new vehicle?
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why not the LS2LS7? 11:44AM (9/08/2009)
Isn't this entire article about how GM does take aerodynamics into account when designing vehicles?
Throwback 11:47AM (9/08/2009)
They do, as does every auto company. The Volt and all EVs benefit more from slippery aerodynamics than most cars. While some ABg posters don't car about aesthetics as long as the car is efficient, most people do care about looks.
paulwesterberg 1:46PM (9/08/2009)
GM doesn't take aerodynamics into account when designing concept vehicles. Since it is the most important thing affecting vehicle efficiency it should be part of the initial design process, not as an afterthought band-aid approach.
It is much cheaper to design things the right way initially rather than going back and trying to fix it later.
Sean 2:23PM (9/08/2009)
@LS2LS7
"Isn't this entire article about how GM does take aerodynamics into account when designing vehicles?"
No, its about how this is the second time GM has tried to make an aerodynamic car. GM is not normally willing to trade 'style' for efficiency because most consumers don't much care about an extra $6k (the difference between 25mpg and 20mpg over 200,000miles at $3 per gallon) in fuel costs and significantly decreased performance.
The difference with the volt is that instead of the consumer paying more for fuel down the line, GM has to buy a bigger battery if the want to sell a poorly designed car.
@Throwback
I understand that some people are willing to pay thousands of dollars extra for a car with worse performance because it looks cool. I agree that GM and the other should make cars for those people, but that can;t be everyone. Can't someone sell a real economy car in this country?
axio.matik 12:43PM (9/09/2009)
Yes, with rising gas prices, people are starting to consider gas mileage more and more. But in the era of $1.30 gasoline, it didn't matter to consumers. Even now, 95% of customers are more concerned with the car's 'attractiveness' than the small gains in mileage from putting aerodynamics first. Yes, the Aptera is very aerodynamic. Guess what, the vast majority of consumers would never even consider it because it is too goofy looking. If you want to sell cars, you first have to design them to be desirable to the consumer, then optimize as much as you can within that envelope. That's what all car companies have been doing for decades.
What other aerodynamics-first designs are out there? Very few. To single out GM for somehow missing the boat is short-sighted, it's not like the Accord looks like an Aptera.
Dan 1:11PM (9/08/2009)
"...adds 7 miles" ? Does this mean that it will get 47 miles city? or are they just saying in order to get the 40 miles they had to get this much in aerodynamics. Knowing them I assume the latter... but hope for the 47!
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why not the LS2LS7? 1:31PM (9/08/2009)
This stuff has been so filtered through marketing it's tough to know what it means. It's possibly some engineer just said "we reduced the drag 18%" and a marketing person spun it into this story.
Either way, I'm with you, I'm not expecting to see over 40 miles. In fact, unless you are in an area of the country with a very temperate climate, under 40 is very possible.
DasBoese 5:02PM (9/08/2009)
And yet, GM made such cars as the Opel Calibra, which at the time of its introduction was the most aerodynamic mass-production car available, and remained that way for a decade.
But yeah, GM never made aerodynamic cars.
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