Don't buy the hype, says GM; Volt's aerodynamics "superior to most, if not all our competition"
2011 Chevy Volt - Click above for high-res image gallery
Back in the 1960s and early '70s, when musclecars ruled America roads, manufacturers were known to either purposely understate (for insurance purposes) or, more likely, overstate horsepower levels in the race to woo buyers to their massively powerful vehicles. Might something similar be happening in today's eco-friendly wars?
According to Chevy Volt Design Director Bob Boniface, yes. In a recent webchat, Lyle Dennis from GM-Volt.com asked how the Volt's aerodynamic properties will compare with other electric vehicles, in particular with the claimed .27 coefficient of drag of Tesla's Model S. Here's what Boniface had to say:
People may think we are skirting the aero issue by not quoting our tunnel figures... If I quote an actual GM-derived tunnel figure, it may not look impressive to you when, in fact, it is superior to most, if not all our competition. It is very much like the horsepower race back in the '60s. The Volt aero performance is second only to the EV1 in GM history.We should have a bit more to go on soon regarding the Volt's aero properties. Boniface also said that GM would soon be testing a new 2010 Prius in its own wind tunnel and expects the Volt to compare favorably with Toyota's hybrid hatchback.
Gallery: 2011 Chevy Volt
[Source: Inside Line]
Reader Comments (Page 1 of 2)
FitFan 7:59PM (7/31/2009)
"... in GM history"
Thanks for the spin, Bob.
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ufgrat 8:21PM (7/31/2009)
Right... after all, GM has only been around since... what... 1908?
And the EV1 has a claimed CoD of 0.19, which is the same as the Prius claims.
So... where's the spin, exactly?
MattP 8:26PM (7/31/2009)
You are terribly wrong. Prius II has a Cx of 0,26 and Prius III (2009) - 0,25.
ufgrat 3:44AM (8/01/2009)
My apologies... don't know where my brain came up with the Prius at 0.19. The Aptera claims 0.15, but apparently the official record is still the EV1 at 0.19. Makes my poor Saturn look kinda wimpy at 0.31.
FitFan 4:15AM (8/01/2009)
I quoted the "in GM history", because GM didn't give a shit about fuel efficiency until they went bankrupt selling gas guzzling SUVs.
Their "history" of making aerodynamic cars is non-existent. Which makes his "in GM history" superfluous marketing spin.
They have one vehicle in their entire history -- the EV-1 -- that was very aerodynamic. By comparing the Volt to the EV-1 and saying that it's the only more efficient car in their history, it gives the uninformed reader the impression that the Volt beat out a large group of efficient vehicles produced by GM, when in fact it only has one car in its class.
It's like placing second in a race between two cars and making it sound like you've achieved something.
I'm pulling for the Volt to succeed. I hope it crushes the competition and inspires other car manufacturers to follow suit. But when a company suit claims that they have fantastic wind tunnel numbers but they can't release them because we wouldn't be impressed ... well, I smell bullshit.
nickoo 5:19PM (8/02/2009)
The GM Leanster must have been pretty aerodynamic, too bad it never went into production. I would have bought one.
Lemon 9:59AM (8/03/2009)
I'm pretty sure that before the recent downturn of the auto industry, GM had more models that could achieve 30+ mpg than any other automaker. Currently, for the classes they compete in, GM models lead almost every class in fuel economy. Also, their "gas guzzling SUV's" just so happen to get better economy than the competitor's thanks to technologies like cylinder deactivation and 2 mode hybrid. Toyota never got the gas guzzling SUV image because they couldn't sell very many of their SUVs. I know many people hate them, but some people need the towing and passenger capacity. To say that GM never cared about fuel efficiency before bankruptcy would be quite naive.
MattP 8:21PM (7/31/2009)
That's simply not true. Prius II had 0,26, Prius III has 0,25 and Mercedes E-Class has 0,24. Plus many contenders in AXP are below 0,2. But what is really important is A*Cx, not Cx on its own. Stop talking about Cx! Let's talk about aerodynamics, which is A*Cx. A very low Cx can be ruined by very large A - that the problem with Aptera.
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meme 11:38PM (7/31/2009)
How exactly is Aptera "ruined" when it reportedly can do 200+ mph at 150hp? By physics, that corresponds to a *maximum* drag area of about about 0.24 square meters, about the same as a Twike and two thirds that of the EV1. That'd be if 100% of its losses were aero and the speed was exactly 200mph. In practice, that probably means its drag area is more like 0.20 square meters -- rolling and ancillary losses won't be much at those speeds, but drivetrain losses still will.
why not the LS2LS7? 2:11AM (8/01/2009)
The Aptera can't do 200mph.
meme 2:47AM (8/01/2009)
Aptera refused to "confirm or deny" whether they've taken it up that fast when they provided those numbers, but have stated that's its horsepower requirement from that speed. So if it's real-world, them's the numbers, and even if it's calculated, that means that's the drag area being used in their calculations.
MattP 4:21AM (8/01/2009)
Meme, Cx is constant. Either A*Cx is 0,24 m sq or 0,2. But Aptera stated that A*Cx of prototype (without mirrors and Cx=0,11!!) was 2,98 ft sq, what is 0,277 msq. The production version has Cx of 0,15 what increas the drag to the level seen in EV1 (ca. 0,37 msq). So essentially Aptera is a new EV1, in terms of aerodynamics (at least until I'll see better oficial figures from Aptera) - but over 2 meters wide. TWICE as wide as very efficient tandems designed with urban commuting in mind.
BTW, doesn't it say anything that Aptera is talking all the time about Cx of 0,15 but did not reveal the A figure?
NeilBlanchard 6:13PM (8/01/2009)
Hi Matt,
The frontal area of the Aptera 2e is pretty low: from my own (approximate) measurements, the area is taken from a long lens photo, and measured with a polyline tracing the outline in DataCAD: 19.881 sq. ft. The factory Cd is 0.15, so the CdA is 2.98.
Sincerely, Neil
MattP 3:46PM (8/03/2009)
Thank you for your correction Niel. OK, so Aptera has around 2,98 ft sq = 27,7 dm sq = 0,277 msq. THAT is the figure Aptera should reveal, not just Cd. It's indeed better then EV1, but my main objection against Aptera is its enormous width which makes it very hard to use for urban commute.
MattP 10:08AM (8/05/2009)
Niel, does is look familiar?
http://www.washingtonautoshow.com/vehicles/detail.asp?type_id=3&make_id=109&vehicle_id=881
That's how Aptera should look like. It could be 1,6m wide as average car, not 2,1 like a full-size SUV.
I wonder is there is any progress with Aptera Palomar aka Aptera 4e - hope it will be no wider then 1,6m!
MattP 8:34PM (7/31/2009)
Without A - frontal area Cx (Cd) of 0,27 says nothing. Volt will be good if A*Cx is lower then 0,5 m sq (eg. A
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wincros 9:01PM (7/31/2009)
People may think we are skirting the aero issue by not quoting our tunnel figures... If I quote an actual GM-derived tunnel figure, it may not look impressive to you when, in fact, it is superior to most, if not all our competition. It is very much like the horsepower race back in the '60s. The Volt aero performance is second only to the EV1 in GM history.
That is the key. It would not look impressive, but will be superior. Contradiction and nonsense in the same sentence. It will be what GM says it is, just like everybody else's. The relatively flat front and the trunk sticking out the rear is far from the ideal of the wedge front and tapered stubby rear of an aerodynamic shape. The only independent testing will be the fuel economy protocol by the Department of Transportation. The rest is BS.
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Murc 11:02PM (7/31/2009)
Who cares about minute things like this...
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Dave 8:27AM (8/01/2009)
+1
The proof is in the pudding:
What will it cost?
Does it actually have a 40 mile EV range? How much does that range decrease with A/C, heat, radio, etc?
And what mpg will it deliver once the batteries are depleted?
The Cd is just a small part of the equation.
Eugene 12:32AM (8/01/2009)
real world range is more important than aerodynamics. why drive a car that is just a little more aerodynamics with a 40 mile range, than a less aerodynamic car that has a range of 100+?
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