Volt's Exterior Design Extends Range

As General Motor Corp. engineers work to solve the mechanical riddle of the upcoming Chevrolet Volt plug-in hybrid, the auto maker tasks designers with creating an aerodynamic body that optimizes the vehicle's efficiency while also resonating with consumers.

To speed the process along, the auto maker recently established a studio on the campus of its Warren, MI, research and development center dedicated solely to the design of vehicles that will use GM's E-Flex propulsion system. Its first project is the Volt, which is expected to come to market in 2010.

Bob Boniface, director of design-E-Flex systems, says his 45-member team has arrived at a body shape that will accommodate the size of the lithium-ion battery that will be used with the Volt. GM engineers and a pair of suppliers currently are downsizing the battery to meet requirements without sacrificing range or safety.

“An exact (Volt) production date has not been set, but when a decision is made, we're ready to go,” Boniface says during a tour of the E-Flex studio, located in a former auditorium that has witnessed speeches by three U.S. presidents.

GM expects to have Volt mules ready by second-quarter 2008. The E-Flex system will combine the Li-ion battery with a small-displacement, internal-combustion engine. Future E-Flex systems could use a hydrogen fuel stack to power the battery, or a small diesel engine.

Either way, GM says the Volt's goal is to travel up to 40 miles (64 km) without using a drop of fuel.

Boniface offers journalists a glimpse of the production-model Volt design by lifting back a veil to expose its passenger-side headlamp. One visible change from the concept model: Designers have softened the sharp corners that typified its blunt nose.

Corners create turbulence, increase drag and lower overall aerodynamics.

Boniface says a separate studio for the E-Flex team means fewer distractions. The main design studios on the 640-acre (259-ha) campus are located at the south end, while E-Flex is located at the northern-most section.

Boniface says a separate studio makes sense because the E-Flex team faces unique challenges, such as packaging a battery that runs nearly the entire length of the Volt's tunnel. That means designers must create many of Volt's components from scratch, with each one meeting low-energy specifications.

“We're inventing as we go,” he says. “You couldn't shoehorn (the Volt) into another studio.” GM organizes its studios by vehicle architecture. “If I used an inefficient component, I could sacrifice electrical range.”

Boniface's team continues to tweak the Volt's exterior design to increase aerodynamics. Since the concept's unveiling at the 2007 North American International Auto Show in Detroit, designers have used aerodynamic research to reduce drag 30%.

Frank Weber, global vehicle-line executive and chief engineer for the E-Flex System, says aerodynamics play a greater role in improving vehicle range during highway driving than does reducing mass. An aggressive improvement in aerodynamics, he says, could improve highway range by up to 5 miles (8 km).

GM performs the Volt's aerodynamic testing at its wind tunnel on the campus, as well. Opened in 1980, the facility operates on three shifts, five days a week, testing every vehicle GM produces.

It ranks as the world's largest wind tunnel devoted to automotive testing. Aerodynamicists start with a one-third-scale model and work progressively to a fullsize vehicle. They're currently at the midpoint with the Volt.

In addition to increasing fuel efficiency, an aerodynamic vehicle can attract consumers, says Ed Welburn, GM vice-president-global design. Creating a vehicle with character is a primary goal of the E-Flex program.

“When the aerodynamicist and designer work together, not only do they influence fuel economy of a vehicle, but I think some stunning shapes can come out of that development work,” he says.

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