Is Volt really an electric vehicle or just a gussied-up hybrid? New questions have been raised about the ways its drivetrain operates.

With the Chevrolet Volt making its official launch this week, General Motors has found itself in the midst of a potentially serious controversy over the precise way the so-called extended-range electric vehicle actually operates – and whether the maker has been honest about its limitations.

To some, GM has engaged in a Watergate-style cover-up, and that message could resonate with those who still call the company “Government Motors.”  To others, however, it’s little more than a tempest in the proverbial teapot and, if anything, just proves that GM is making sure that whatever it takes Volt will live up to its loftiest expectations.

In a Monday news release, GM declared Volt “Reinvents Automotive Transportation.” There’s little question that the new model is a significant improvement over the current crop of hybrid-electric vehicles, like the Toyota Prius, which can operate under battery for very limited distances at low speeds.

As first conceived, Volt was designed to run exclusively on battery power.  Its 16 kilowatt-hours of lithium-ion batteries were intended to give the vehicle about 40 miles range solely in electric mode and at speeds of up to more than 90 mph.

But as the “E-REV” gets ready to launch a few key things have changed.  For one thing, GM now claims that Volt’s battery-only range is more accurately somewhere between 25 and 50 miles, depending upon road and weather conditions and individual driving patterns.

But the real controversy concerns the way the underlying drive system actually operates.

Under some rare circumstances, the I-4 engine can provide direct power to Volt's wheels.

Unlike a conventional battery-electric vehicle, or BEV, Volt has the ability to keep running even after its batteries ran down.  The secret is a small inline-four-cylinder gasoline engine that automatically fires up once the battery charge ran down.  As conceived, this so-called “serial hybrid” design uses the gas engine only to generate electricity to power Volt’s electric motors.

But that’s not entirely accurate, it turns out, for those who take a close look at the patent GM received on September 21^st.  In an effort to improve operating efficiencies – meaning both maximum range and performance – some modest changes were made to the 4ET50, electric drive unit that’s the heart of what GM has dubbed the Voltec propulsion system.

A perusal of notes I have personally taken over the nearly three years since the concept Volt was first revealed – and the stories I have personally written or archived from other sources – clearly indicate that at no time would the gasoline motor on Volt ever provide direct power to the vehicle’s wheels.

In fact, there are conditions where that can happen, acknowledges Volt’s program chief, Tony Posawatz.

To be clear, he told TheDetroitBureau.com during a lengthy interview, under the vast majority of circumstances, Volt “can only run with the traction (electric) motors.”

But there are some situations where the strategy has shifted.  This occurs only when the batteries have run down and the vehicle is operating in so-called “extended-range mode.”.

These are high-demand “very rare circumstances,” when you’re “running about 70 mph and you tip in” to pass, says Posawatz, or where a fully-loaded Volt is trying to accelerate up a long, steep hill.

In such a situation, the complex set of gears and clutches in the 4ET50 will draw what the GM executive describes as “a small amount” of power directly from the I-4.  In other words, some of the gas engine’s torque will be added to the power of the electric motors to handle the load and, Poswatz stresses, to help improve the overall efficiency of the Voltec drive system.

That’s not unlike what happens with a regular hybrid, like Prius, though Posawatz insists it happens far less frequently and, most importantly, that the electric motors are always operating and providing the vast majority of torque under all circumstances.  There is never a situation where the wheels are driven directly by the I-4 engine alone.

Nonetheless, in an angry denunciation, Edmunds.com sums it up by declaring, “Frankly, we were lied to.”

Is that a fair characterization?  No, GM officials contend.  For his part, Posawatz insists, “No program has been as open and transparent on something as far reaching and innovative” as Volt.  “We have not fully disclosed the information, I will grant you that,” he says, suggesting that was, in part a strategy while waiting for the patent approval, but Posawatz adds that, “We have not been intentionally deceptive.”

Perhaps not, but the brouhaha raises a number of questions.  For one thing: what exactly is the 2011 Chevrolet Volt?

One could now argue that it is just a fancier hybrid, and not a true electric vehicle.  Then again, nobody has ever come up with a singularly acceptable definition of an extended-range electric vehicle.

But that could become an issue for those who might now challenge the idea that the Volt should qualify for the government’s $7,500 tax credit, which is also offered to pure battery-electric models, like the Nissan Leaf.

The more important question is how consumers will react.  Posawatz and GM’s supporters will say that the modified driveline actually will serve consumers better by ensuring the Chevy Volt can perform as expected under the widest range of operating conditions.

But there’s also the possibility that if this flap gains enough media traction it just might scrape the chrome off the halo Volt was intended to give the long-troubled General Motors.  The maker simply doesn’t need the bad publicity just as Volt is getting ready to come to market – and as GM prepares for its long-awaited IPO.