????Performance, price, and value - there's still a lot of gray area around GM's electric car.

????By Alex Taylor III

????While General Motors continues to define itself post-bankruptcy, it is pushing ahead with one of its key pre-bankruptcy projects: developing the Chevy Volt.

????This week, a team of GM vehicle engineers is testing eight battery-powered Volts on a three-day, 1,200-mile drive from southeast Michigan to Pittsburgh.

????The engineers will evaluate everything from the sound system to the seats, but most of their attention will be focused on how the Volt performs under electric and gasoline power.

????Lots of questions remain, as I discovered when few a words about the Volt at the end of my last column drew a number of heated responses.

????My comments focused on speculation about the performance of the Volt after the batteries discharge and the range-extending gasoline engine kicks in.

????Sine the Volt weighs close to 4,000 pounds, according to a knowledgeable source, and the engine only displaces 1.4 liters, some have guessed the Volt would be a slacker under gasoline power.

????"Absolutely incorrect," says a GM spokesperson. "There is no degradation in the Volt's performance after the battery has reached its lower state of charge. The engine-generator provides sufficient power to propel the vehicle."

????GM says that the Volt will be able to accelerate from zero to 60 miles per hour in 8.5 to 9 seconds, whether it is running on battery or engine-generator power

????That's not all. Also under scrutiny is GM's oft-repeated assertion that the Volt will have an all-electric range of 40 miles. Critics point out that the car needs ideal conditions to do that.

????For one thing, the 40-mile range depends on ambient temperatures of 60 degrees to 65 degrees. When the temperature drops below 60, the batteries become less efficient. And if it gets hotter than 65, the air conditioner can impose an additional load on the Volt's batteries. Either way, the range diminishes.

????Nor does the 40-mile range accommodate aggressive driving or sustained uphill climbs -- you don't have to be a budding drag racer or hill-climb contestant to get less than the full range on electricity.

????Other questions about the Volt are almost philosophical: Just what is GM is trying to achieve with the Volt, and how much value does it provide the customer?

????For instance, compare the Volt to the best selling gasoline-electric hybrid, the Toyota Prius. The goal of the Prius is to use less gasoline. Therefore, it carries 230 lbs of batteries that give an assist to the 1.8 liter gasoline engine to improve the car's fuel economy. The Prius has an all-electric range of only about a mile, but it gets 50 miles per gallon of gasoline.

????And oh yes, the Prius starting price is $23,750.

????The Volt, in contrast, wants to almost entirely do away with gasoline. Therefore, it carries a hefty 400 pounds of batteries that can propel the car up to 40 miles under ideal conditions. But once the batteries have been depleted, the Volt is powered by a conventional 1.4-liter gasoline engine that gets conventional fuel economy.

????And the price for the Volt hasn't been set yet, but it will likely be a tad under $40,000, minus a $7,500 government rebate -- a good bit higher than the Prius.

????So here's one way to look at: The Volt will be easier on the environment, but only if you don't mind paying a premium and drive fewer than 40 miles per day.

????The Prius weighs more heavily on the environment but performs consistently under nearly all conditions and cost less.

????Choosing between the two will be up to customers, beginning at the end of 2010 when Volt is scheduled to go on sale.