The technical direction it has pioneered is the way of the future
General Motors’ hopes that the Chevrolet Volt would trigger a renaissance for the company as a technology leader seem to be evaporating along with sales of the revolutionary vehicle.
Perhaps the most-publicized new car ever, over the longest pre-launch period ever, the Volt was in many ways old news before it came to market. But the news it has generated since then appears to have undermined the positive vibe that all the early buzz generated.
At the heart of its negative publicity is a fire that broke out in a Volt test vehicle after a side-impact crash test conducted by the U.S.-based Insurance Institute for Highway Safety (IIHS) — three weeks after the crash, while the car was in storage!
The cause was apparently related to a failure to properly discharge the damaged battery after the crash — something that could quite feasibly occur in the real world. But, as one cynical observer put it. “Three weeks should be more than enough time for anyone to get out of the car.”
Viral fire spiralled
GM acted quickly to reinforce the structure and prevent battery damage in the affected area, both in cars already sold and those subsequently produced. But the damage had already been done. Hyped by aggressive media, news of the Volt’s “fire risk” went viral.
Whether as a result of that negative publicity, public apathy to the Volt’s pioneering technology, or the price premium such a technically complex car demands, sales of the already slow-selling halo vehicle stalled further, resulting in temporary plant shutdowns to adjust inventory. Which in turn supported the impression that the Volt is undesirable.
It deserves a better fate. Time is likely to prove that the technical direction the Volt has pioneered is indeed the way of the future.
The fact is, the mandated fuel-economy levels that new vehicles must achieve going forward as far as 2025 can’t be met with minor tweaks to current gasoline-engine technology. Some more radical solution will be necessary.
Canadian option
One alternative, strongly supported by many political and environmental factions, is battery electric vehicles (BEVs). And they will find a place in the market, primarily for inner-city use. But the limited range of those vehicles, along with the extended time needed for recharging, effectively limits their potential for mass-market appeal in a country as vast as Canada, where daily driving distances routinely amount to hundreds of kilometres.
Hybrids are a more attractive alternative for the mass market, using electric power generated on board to offset some of the power requirement of the internal combustion engine. But the so-called “Voltec” technology used in the Volt (and other GM vehicles in the pipeline) goes a step beyond conventional hybrids, in three ways.
First, by plugging it into the electricity grid, it charges its batteries without the use of the engine. In that respect, it is similar to a more-conventional plug-in hybrid.
Second, its engine is connected primarily to a generator, not directly to the wheels so it can be operated within a narrower and much more efficient range of speed and load than in a conventional drivetrain — the classic definition of a series hybrid.
Third, it employs a very sophisticated continuously-variable transmission (CVT) module that permits operation in four different modes — two pure electric and two that combine use of the electric motors and gasoline engine.
Unlike most other CVTs, it comprises primarily a single planetary gearset — sun gear, five planetary gears and their carrier, and ring gear — similar in concept to those used in conventional automatic transmissions.
A sophisticated computer control system engages and releases three separate clutches to permit power-flow seamlessly through the gearset in four different ways, corresponding to the four modes of operation.
Modes 1 and 2 are pure electric drive. A large electric motor is used for startup, initial acceleration and low-speed operation, where it is most efficient. A second, smaller electric motor, which also serves as a generator, is engaged to supplement the primary traction motor at higher vehicle speeds where it is more efficient.
Mode 3 also employs the second motor, but as a generator, driven by the gasoline engine, while Mode 4 also permits the engine to contribute some power directly to the wheels — parallel hybrid operation.
The sophistication of the system allows efficiency to be optimized over a much broader range of conditions than is the case for other alternatives. Which is why, in spite of the Volt’s market challenges, several other automakers are hard at work developing similar systems of their own.
