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August 1, 2008
Volt aero and styling: Touring the E-Flex design studio and GM wind tunnel - AutoblogGreen
Before taking AutoblogGreen and others to the design studio on Monday, Frank Weber, the Vehicle Chief Engineer for the Volt, talked about the effect of aerodynamics and other factors on vehicle efficiency. Driver behavior is clearly a factor for both traditional and electric cars. Beyond that, on traditional cars, factors like mass, aero drag and rolling resistance come into play in that order. In testing and simulation GM has found that for electrically-driven vehicles mass actually drops to third on the list behind aerodynamics and electrical loads with rolling resistance coming in fourth.
Working from the Volt's forty mile target range, it has been determined that a 400 lb. swing in mass only has a two-mile effect on range on the city driving cycle and only a one mile effect on the highway. While every mile and pound counts, this turned out to be much smaller than the effect of aerodynamic drag. Intuitively, most people expect that aerodynamic drag has an impact on the range and efficiency of a vehicle at highway speeds.
This of course is true with a forty count reduction in drag coefficient (for example going from .300 to .260) having a six mile impact on range at highway speeds. The impact at city speeds is the big surprise. Here the same aerodynamic drag reduction causes the range to increase by four miles, more than double the effect of a 400 lb. weight reduction.
Posted by thdyck on August 1, 2008
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