Chevrolet Volt's aero efficiency

• Teaser image shows wind tunnel work
• Aerodynamics now 30% more efficient
• Testing to begin in 2008, on sale in 2010?

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• More pictures

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This teaser image shows the latest incarnation of the Chevrolet Volt electric car.

The Volt is powered by a battery which can be charged by a tiny on-board engine if necessary.

Although the picture gives little away, it shows a significantly more aerodynamic car than the original concept vehicle.

Work in GM's wind tunnel in Michigan, USA, is reported to have reduced the Volt's drag by 30%, making it around 7% more energy-efficient.

In addition, engineers have had to balance the need for aerodynamic efficiency against the requirement to achieve enough under-body airflow to cool the battery pack.

Road testing of the Volt is set to begin in 2008, with a production version of the car likely by 2010.

Latest figures suggest it can run for 40 miles on battery power alone, which would be sufficient to power two-thirds of commutes in the USA.