The Chevy Volt’s Voltec powertrain might not be as special as we’ve been led to believe. Then again, maybe it’s even more so.
After several initial reports about the car’s electric drive/hybrid system GM has issued a press release to clarify exactly how it works, stating that specifics were never given in the past as the automaker awaited patent approvals. After some initial tests by and interviews with a few of the auto industry’s buff books, it was recently revealed that contrary to all past claims by GM, the Voltec system is not a pure extended-range electric vehicle (ER-EV), but that under certain circumstances the 1.4-liter gasoline engine can actually power the wheels. In that sense, the Volt seems like little more than a plug-in Prius (parallel hybrid) with a larger and more powerful battery and electric motor.
That, however, is not entirely true either, as GM says the gasoline engine still cannot power the electric wheels on its own. In fact the gasoline engine can power the wheels, but only in addition to the electric motor powering the wheels and only under certain circumstances. One example GM gives is during certain types of extended-range driving (once the initial plug-in power has been depleted) the gasoline engine feeds a small amount of power to the wheels. “The resulting power flow provides a 10 to 15 percent improvement in highway fuel economy.”
What this all means is that the Volt first operates as an electric vehicle, and then it switches to be both a series hybrid (extended range electric vehicle) and a parallel hybrid (like the Prius) depending on the type of driving.
A pure electric vehicle it might not be in the strictest sense of the word, but a technological innovation it most certainly still is.
Official release after the jump:
Chevrolet Volt Electric Drive: Engineered for Efficiency
DETROIT – As GM has started the media launch program for the Chevrolet Volt, some confusion has emerged about details of the Volt’s drive technology.
The engineering of the Voltec electric drive unit is very sophisticated. As part of the media launch, we’re diving deeper into how the system works than we have in the past. We did not share all the details until now because the information was competitive and we awaited patent approvals. Following a small number of inaccurate media reports, we want to clarify a few points.
The Volt has an innovative electric drive system that can deliver power in both pure electric and extended range driving. The Voltec electric drive cannot operate without power from the electric motors. If the traction motor is disabled, the range-extending internal combustion engine cannot drive the vehicle by itself.
There is no direct mechanical connection (fixed gear ratio) between the Volt’s extended-range 1.4L engine and the drive wheels. In extended-range driving, the engine generates power that is fed through the drive unit and is balanced by the generator and traction motor. The resulting power flow provides a 10 to 15 percent improvement in highway fuel economy.
Our overriding objective in developing the Voltec electric drive was to deliver the most efficient, yet fun-to-drive experience in both pure electric and extended-range driving. We think our unique technology lives up to its most important promise: delivering our customers with the only EV that can be their primary vehicle, with EV operation for normal daily driving, and extended range driving for weekends, holidays, and longer trips – all with no range anxiety.
To read what journalists who have spent time with the Volt have to say, please click the links below:
Unbolting the Chevy Volt to See How it Ticks (MotorTrend.com)
“On paper, the Voltec drivetrain has more in common with a Prius (and other Toyota, Ford, or Nissan Altima hybrids) than anyone suspected. Each system employs a single planetary gear set, a gasoline-powered piston engine, and two electric motor/generators. But the way Chevy connects them is entirely different, and – if you ask me – superior.”
Chevy Volt Surprise (Automobilemag.com)
“To trump both the Prius and the Leaf, Volt combines their merits in one handy advanced-technology sedan. It employs cheaper and cleaner electrical energy drawn from the grid. It provides efficient electric drive without the usual compromises. It uses gasoline intelligently in a supporting role. It is a pure electric, a series hybrid, and a parallel hybrid all rolled into one.”