Accelerating from a stoplight, the only clue that the Toyota Prius is transitioning from pure-electric to blended gasoline-and-electric propulsion is a tremor so subtle that passengers never notice. An advanced four-cylinder engine starts up and shoulders its share of the load as stealthily as a thief in the night. In fact, the Prius is such a smooth operator, the electronic pictograph display in the middle of the dash is the only sure means of knowing exactly how the front wheels are energized at any given moment.
For all intents, this is Toyota's "Mission Impossible" — a production car engineered to overcome the inherent drawbacks of a pure-electric: high cost, limited range, and the logistical headache of recharging batteries. So far, it's off to an illustrious start. Toyota launched Prius in Japan with a bargain price tag (about $17,500) in hopes of selling a thousand cars per month. Customers overwhelmed that goal with 3,000 orders the first day this car hit the market.
What the Japanese are clamoring over is nothing less than the world's most sophisticated powertrain ever delivered to ordinary customers. The front wheels are driven by computer-controlled combinations of power supplied by a 1.5-liter 58-horsepower gasoline engine and a 40-horsepower alternating-current permanent-magnet electric motor-generator. A smaller motor-generator starts the gas engine, supplies a portion of the electric motor's power, and recharges 40 nickel-metal hydride batteries stored in the trunk. An ingenious planetary gearbox helps manage the complex flow of mechanical and electrical energy. In addition to its futuristic propulsion system, Prius boasts the interior room of a Camry with a length that's nearly half a foot shorter than a Corolla, an extra-efficient climate-control system, and electric (instead of hydraulic) power steering.
Prius gets the acid test
Tested on a Japanese driving cycle (where the car is at rest more than a third of the time to simulate congested traffic), Prius undercuts local emission limits by 89 percent while delivering 66 mpg. In EPA tests that better reflect U.S. driving conditions, results are not as good — 47 mpg in city driving and 37 mpg on the highway — but still better than practically every other fossil fuel burner on the market. To pinpoint its performance, we tested a Prius side by side against a dead-conventional (but similar in size and price) Toyota Corolla.