"When the battery is depleted, a 1-liter, three-cylinder turbocharged engine spins at a constant speed, or revolutions per minute (rpm), to create electricity and replenish the battery."

Instead, we're now being told, via the press release from last week's production reveal:

"a gasoline/E85-powered engine generator seamlessly provides electricity to power the Volt's electric drive unit while simultaneously sustaining the charge of the battery."

So, after some portion of the initial 40 miles of all-electric driving depletes the battery, the engine will be used to "sustain charge" while powering the electric drive directly — and not to charge up the battery. Perplexed by this apparent change in course, we placed a call to Chevy spokesman Terry Rhadigan to find out more — and figure out why the Volt isn't just a regular hybrid?

According to Rhadigan,

"The reason it does that is because we want you to arrive with the batteries 'empty,' filling up on grid power costs about 1/6th of what it does with gas."

In this sustaining charge mode, the Volt never actively tries to recharge the battery. Energy from regenerative braking is dumped into the battery, but at stop lights the engine will actually power down, saving gas rather than recharging the battery as we'd always thought. We incorrectly assumed, after our conversation on the Volt using GPS to determine efficient charge capacity on the battery with "Maximum" Bob Lutz at the production Volt reveal, it would do just that.

So basically, the Volt's not a hybrid because it still only has one drivetrain, an electric one. The engine makes electricity to power the electric motor running the wheels as well as to "sustain" the batteries, but not to charge them up. It's still, we guess, an Range-Extended Electric Vehicle (REEV), as GM's always claimed.

We don't know how to feel about this news. Certainly, from an engineering perspective and total cost of operation, it does make sense. That 1.4-liter four-banger doesn't have the power to both motivate the quite-beefy Volt and recharge the battery pack, and it probably allows the on-board generator to take advantage of constant RPM efficiency tricks. But, it again tells us we must keep our guard up on the marketing spin here. There's no doubt the Volt has changed the way hybrids are developed already, but it may also change the ways they're sold to the public. [Edmunds Inside Line]

Combined with the planned GM 100th anniversary production skin reveal coming up ahead of the 2008 Woodward Dream Cruise, we're just about to the point of knowing all there is to know about the Volt.

Jalopnik Snap Judgement: This is the right way for GM to go with this program. The original Volt concept had a 1.0-liter turbocharged three-cylinder — little more than a snowmobile mill. The 1.4-liter will offer the reliability of a regular production engine but just as importantly, reduce the number of engine lines GM has to run. In fact, thanks to the news from those leaked UAW documents that the Volt would be built in GM's Hamtramck plant and the Cruze will be built in the Lordstown, OH plant — they'll only need one engine build location near the two — like the expected Flint engine plant.

With your average engine costing about a billion bucks to develop and put to production, and the weight and packaging between the two engines being about the same, this one is practically a no-brainer. Now, if only they'd turbocharge it for a Volt SS! Yeah, 'cause that'd be cool. Actually, no it wouldn't be.

[via Automobile Mag]