The Opel Flextreme's range extender is a turbo-diesel engine instead of the internal combustion variety used in most American cars.

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The Future of E-Flex

Unveiled at the 2007 North American International Auto Show (NAIAS), the Chevrolet Volt is the first vehicle on the E-Flex platform. Unlike the two-seat, two-door EV-1, the Volt is a four-door compact sedan with four seats. The interior should accommodate a 6-foot 2-inch man comfortably in the front and rear seats. The lack of a center seat in the back will allow room for the car's battery in the center of the car and keeps the roof low for better aerodynamics. In order to get the fuel economy GM wants, the Volt will be extremely aerodynamic.

It's going to take some work: Many have called the Volt's release timetable extremely ambitious. GM wants to have the cars on the road by the end of 2010, and that means extensive testing of the battery and development of the car itself.

The battery has to stay cool. It has to be safe. It has to handle bumpy roads and must be mass-produced as well. Engineers must also have the car itself -- everything the battery operates, in essence -- ready to go by the release date.

The company had targeted $30,000 as a reasonable price for the Volt, but in recent months, GM officials have waffled on that number and told reporters that the Volt's price would be linked to the price of gasoline at the car's launch [source: Blanco].

"Pricing of the Chevrolet Volt has not yet been determined," Darovitz said. "We will evaluate many factors including government tax credits, customer benefits and value, other subsidies, electricity cost versus gasoline savings and initial volumes before we finalize the price."

A few months after unveiling the Volt, GM introduced its cousin, the Opel Flextreme. An E-Flex vehicle aimed at the European market, it's a stylish five-door hatchback with the same heart as the Volt. The only exception is the Flextreme's range extender, which is a 1.3-liter (1,300 cubic centimeters) turbo-diesel unit rather than the Volt's internal combustion engine. This makes the Flextreme better suited to European countries like Germany, Opel's home market, where diesel fuel powers most vehicles.

In January 2008, the Cadillac Provoq SUV hit the auto show circuit. It uses an E-Flex system coupled with hydrogen fuel cells to deliver a vehicle that can drive 280 miles (451 kilometers) on hydrogen and 20 miles (32 kilometers) on electric battery energy -- all while giving off no emissions except water vapor.

While the Volt, Flextreme, and Provoq are all still in the concept stages, Farah said the E-Flex components are designed for use in a wide range of vehicles. "We should be able to broaden the availability of this kind of technology, to put it in all kinds of different cars people want," he said.