Driving The Precurser of the Toyota Prius Hybrid

Before the Prius was born, the Toyota Hybrid System was being developed in a nondescript Toyota sedan. Green Car editors drove this at Toyota's Arizona proving grounds in 1997 and knew immediately that the electric drive field would change forever. The hybrid system was unlike any others before it, creating a hybrid variant of traditional gasoline-electric hybrid designs of the time. It would run on an electric motor, an efficient internal combustion engine, or both depending on driving conditions. It did this using an all-new transmission with a power-split device and a host of other advanced technologies. Here, we share our editors' thoughts in an original report just as it ran in Green Car's July 1997 issue.

DRIVING TOYOTA'S SECRET HYBRID WEAPON
ORIGINALLY PUBLISHED JULY 1997 After all the research and development, the media hype and the lofty corporate positioning, there comes a time when the reality of a product launch separates leaders from followers.

In the electric vehicle field, this occurred nearly a year ago with the debut of GM's EV1 electric car. Now with a stunning introduction from Toyota Motor Corp., we're set to enter an even more exciting phase of worldwide EV commercialization.

The automaker has developed a highly sophisticated hybrid electric sedan that will be mass-marketed to the Japanese market in 1998. Unlike most other hybrid designs, this car is designed to be powered by an electric motor, a highly-efficient 1.5-liter internal combustion engine, or both. A generator allows the internal combustion engine to charge the vehicle's nickel-metal-hydride battery pack as it drives.

The Toyota Hybrid System uses a newly-developed advanced transmission and precision engine management controls to help make all this happen. A power-split device transmission uses a planetary gear to constantly vary the amount of power supplied from the engine to either the wheels or the generator.

The engine, equipped with Toyota's Variable Valve Timing with intelligence system to provide the highest efficiency and lowest emissions, is designed to run at a maximum of 4,000 rpms. This allows the use of lighter and smaller parts, which helps achieve much higher levels of efficiency. The end result is a hybrid vehicle that nearly doubles the fuel efficiency of internal combustion engines while significantly reducing tailpipe emissions.

Driving the Toyota HEV is exciting in one sense, yet rather anticlimactic in another. This is a good thing. The powertrain concept is so unusual, when test driving the car an inordinate amount of attention is devoted to determining just how different this car feels on the road.

Here's the issue: Even though the engine is starting and shutting off, and propulsion is alternately being supplied by the internal combustion engine, the electric motor, or both depending upon load ... there's little to notice. Certainly, transitions aren't as seamless as they will be when this car is manufactured as a production model. But, our time behind the wheel proved it was seamless enough so our test drive on the track felt quite normal.

Functionally, we started out on electric power only, then the powertrain switched over to the internal combustion engine as speeds increased. As driving needs required additional acceleration, both the electric and internal combustion powerplants would come on line to provide needed power.

We found it interesting that as speeds fell below 40 mph while braking, the engine quietly shut down to conserve fuel. This is an especially useful function in stop-and-go driving. When accelerating again, propulsion was solely electric until we reached the point where the engine was needed for higher speeds, and it would silently rejoin the active powertrain. This whole experience was quite transparent.

Green Car editors asked Toyota about durability issues, considering the complexity of the powertrain and the large number of times the internal combustion engine will be starting and stopping. Toyota engineers admit this is an area of concern, but they say they'll have thoroughly worked through it by the time this vehicle comes to market.

The new Toyota hybrid will carry a price premium. Company sources tell Green Car that buyers in Japan will pay about $4,000 more for the Toyota hybrid than a comparably-equipped internal combustion engine vehicle. Still, when you consider the substantial fuel costs saved due to this car's very impressive 60 mpg fuel economy, many consumers will find that this extra investment is worth making.

Will this car be coming to the U.S. market? It seems likely that at least the powertrain, if not the platform, will make it to these shores. In discussions with Toyota Motor Sales U.S.A., one executive admitted to Green Car editors that the company wanted this car badly. That's easy to understand considering the environmental and technology statements it makes, and the obvious benefits it would bring to the automaker's efforts in meeting Corporate Average Fuel Economy (CAFE) targets.

In the interim, this car's drive to market proceeds apace in Japan. Toyota is building a production line for the hybrid car at its Aichi Prefecture plant, with an eye toward production runs of up to 1,000 units per month beginning later this year.