The ranks of dedicated electric cars--those designed from scratch as plug-in vehicles--are thin.

Come December, a fourth entry, the 2014 BMW i3, will join the three currently on the market (the Nissan Leaf, Chevrolet Volt, and Tesla Model S).

BMW officials confirmed last Thursday that the first i3 models would go on sale in the U.S. very late this year.

The initial batch of i3 models will all be fitted with the ReX range-extending two-cylinder engine, an option on the battery-electric BMW.

BMW executives also confirmed that the i3 will not be as powerful when operating on its ReX range-extending engine.

The sub-1-liter twin will double the i3's battery range of about 80 miles, using about 3 gallons of gasoline in the process--but the performance "will not be as agile" when operating on its gasoline range extender, said BMW CEO Ludwig Willisch.

In an interview published Thursday in trade journal Automotive News, Willisch said the i3 ReX would not have "full power when it runs on the combination" of battery and engine.

The electric motor of the i3 drives its rear wheels--giving the BMW electric car the promise of traditional "ultimate driving machine" handling and roadholding--and the tiny range extender actually fits next to it under the car's rear deck.

But the range extender only powers a generator to produce current that powers the traction motor; the little engine won't drive the wheels directly.

The production version of the 2014 BMW i3 will make its debut at the Frankfurt Motor Show this September, with deliveries in Germany starting a few weeks later.

The i3 won't be available in volume at U.S. dealerships until the early part of 2014, BMW has said, but the latest news appears to indicate that at least a few units will be sold this December.

Neither prices nor range ratings for the i3, with or without the gasoline ReX range extender, have been released.

That likely won't happen until after the September unveiling.

But its now-confirmed arrival date means that in the three years starting in December 2010, the number of dedicated plug-in electric cars on the U.S. market will have gone from zero to four.


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