The Chevy Volt Gets a Wind-Cheating Shape

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Don’t expect the 2010 Chevy Volt to look exactly like the concept car. GM officials assure us that it will be recognizable as the Volt, but aerodynamic considerations are taking priority over the original concept’s bold styling statement. In real terms, this means the production car will not sport the same muscular profile that led some to say it looked like an “electric Camaro.”

At a dinner with media prior to the 2007 LA Auto Show, a candid GM vice chairman Bob Lutz commented that the Volt’s initial wind tunnel results were disappointing … joking that they might have had better results if they put it in backwards. The science of aerodynamics often has little relationship to what we might find visually appealing. As a concept the Volt’s goal was to capture attention, something it did in huge measure. In fact, Volt attracted more than just attention. It immediately captured the hearts and minds of both car enthusiasts and environmentally conscious individuals searching for cleaner transportation solutions.

Clearly, aerodynamics are critical to the overall energy equation. Wind resistance, or aerodynamic drag, is responsible for roughly 20 percent of the total energy required to move a vehicle down the road. Minimizing aerodynamic drag can deliver substantial improvements in fuel economy. Aerodynamic improvements are also among the most cost effective ways to increase fuel economy – more so even than weight reduction techniques that often require the use of expensive and light weight high-tech materials.

Since the Volt is to be GM’s flagship economy champ, it’s critical that this vehicle is as slippery as possible. On a recent tour of the GM Aerodynamics Laboratory in Warren, Michigan, Green Car observed a highly camouflaged one-third scale Volt model in the wind tunnel. This apparently is not a rare occurrence. Those close to the project say the Volt has already spent more time in the wind tunnel than any current GM project.

One of the big surprises to emerge from the Volt’s aero development has been identifying the extent to which wind drag affects the relatively low speed city driving cycle. In an environment where economy is measured in fractions of a mile per gallon, GM is finding major city mileage gains with its dynamic aero refinements on the Volt. Naturally, highway mileage increases at an even greater rate because of the higher speeds and greater wind resistance involved – in fact, more than twice as much as the city cycle when significant aero improvements are discovered.

During our explorations at GM, E-Flex design director Bob Boniface allowed a peek beneath several layers of covers at the front and rear corners of the current car’s full-scale clay models. This tease beneath-the-covers highlighted just a few of the deviations from the concept. The corners are now rounded to allow air to flow smoothly over and around the profile without separating, which increases drag. The rear deck area behind the roofline has also been raised, transitioning to the rear of the car at a less severe angle than the concept Volt. This change prevents air from tumbling off this surface at the rear of the car, which produces considerable drag.

GM is tight lipped about the Volt’s coefficient of drag (Cd), which is the industry standard measurement of a vehicle’s aerodynamic performance. However, we are told by Ed Welburn, GM vice president of Global Design, that the current design offers a whopping 30 percent aerodynamic improvement over that of the original Volt concept car. That said, Welburn won’t comment on which direction the Volt concept was pointed...