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GM: Aerodynamic design boosts Volt's range

Bob Boniface: No sharp corners
TRAVERSE CITY, Mich. — The design team for General Motors' Volt plug-in hybrid car has added six to seven miles to the car's electricity-only range by improving aerodynamics.

"Air does not like to go around sharp corners. It creates turbulence and drag," Bob Boniface, GM's director of design for the Chevrolet Volt and E-Flex studio, said last week at the Management Briefing Seminars here.

So Boniface made numerous changes to the original concept's design. The goal: a 40-mile range per full electric charge. More than 70 percent of U.S. commutes are less than 40 miles, GM says.

Boniface explained a number of the changes.

-- The concept originally had a blunt front with a sharp crease on the corner. The production version has a rounded look.

-- The production car's grille texture is largely sealed, sending air down the side of the car instead of through the engine compartment.

-- A curving crease down the back corner of the concept has been smoothed. Both there and on the spoiler, Boniface said, GM wanted the design "so air leaves the car very quickly and cleanly." GM added 5 millimeters to the spoiler, he said.

-- The concept's sideview mirror started with a patch mount, where the structure holding the mirror extends horizontally from the door. For the production version, that was changed to a post mount. The mirror now sits on a post lifting from the vehicle's side and allows air to flow past more freely.

A slide shows the differences made in the production Chevrolet Volt from the concept version. Photo credit: JOE WILSSENS
The changes to the mirror and spoiler each cut drag by five counts, he said. "Why should you care, when you probably don't even know what a drag count is?" he added.

Designers care because taken together, tiny changes can yield significant improvements.

For every 10 drag counts of reduction by the aerodynamic design, the design team added 0.55 miles of highway range on the vehicle's electric charge.

In total, the team cut the concept's drag counts by 120, thereby adding six to seven miles to the car's range on the charge. Those efforts are helping GM reach its target range of 40 miles on the electric charge for the Volt.  

You can reach James B. Treece at jtreece@crain.com

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