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.
2000 Toyota Prius
Release the brake pedal, and Prius creeps ahead like any automatic-transmission car but without a sound. When you tap the accelerator, it hums quietly on its way. At 10 mph or so (depending on the heft of the driver's right foot), the gasoline engine wakes up to assist the electric motor. Lift off, and there's a soft whine as electrons rush back to the battery during regenerative braking.
This polished power delivery makes the Corolla sound and feel boorish by comparison. At rest, the loudest sound in the Prius is a ventilation fan that registered a remarkably low 27 dBA on our sound meter versus the Corolla's 49 decibels. Splitting the acceleration effort between a small gasoline engine and a smooth electric motor is also a quieter means of running up to cruising speed. Compared to the Corolla, Toyota's new energy champion shows a four-decibel advantage during acceleration to 60 mph.
The performance pitfall
Make that quiet but not quick. With a total power-to-weight ratio that's a third poorer than the Corolla's, Prius takes its time gathering speed. Under optimum circumstances, the run from 0-60 takes 14.5 seconds, which is slower than practically every car and truck on the U.S. market. But if the batteries are unable to assist due to some recent strenuous use — such as climbing a grade — acceleration to 60 can easily require more than 20 seconds. Prius never feels particularly sluggish in ordinary traffic until you venture into the passing lane with the pedal flat on the floor. Between 30 and 50 mph, it runs practically neck and neck with the Corolla (with batteries up to assist) but lags noticeably behind at highway passing speeds. All recharging is handled automatically on the roll when the engine gets a break from running flat-out to satisfy acceleration demands.
The sheer physics of extra weight, a higher center of gravity, and skinnier tires suggest that the Prius might falter in braking tests, but our fifth wheel reported otherwise. In fact it beat the Corolla's best performance — a 60-0 stop with warm brakes in 146 feet — by a substantial 18 feet. Both cars were equipped with anti-lock brakes.
2000 Toyota Prius
To compare the two Toyotas' efficiency, we drove them nose to tail for a full eight-hour stint in Ann Arbor, Michigan's, worst shopping-season traffic (average speed: 18 mph). Each car experienced the same time-speed-distance conditions, yet the Prius was able to top the Corolla's fuel efficiency by an impressive 25 mpg (57 mpg in the Prius versus 32 mpg in the Corolla). On a 365-mile highway run to visit relatives while burdened with a family of four, their luggage, and one beloved pet, Prius registered a respectable 36 mpg.
There are plenty of visual clues that Prius is a very different breed of automobile such as unusual exterior proportions, a flat front floor, and a centralized instrument cluster, but several of its attributes are subtle in nature and only revealed after several days behind the right-side steering wheel. The turn circle is significantly tighter than the Corolla's as an aid to negotiating the tight and congested streets in Japan. The ride is relaxed and well-cushioned thanks to a wheelbase that's long in comparison to this sedan's overall length. The very upright body leans precipitously in tight turns, so sporty driving isn't encouraged. At high speeds there's noticeable wind wander, probably due to the long cabin riding atop very narrow tires. With batteries stowed immediately behind the back seat, trunk room is modest, and the handy fold-down backrests that are standard fare in most compacts are absent.
As an engineering exercise, the Prius is a worthy achievement. But marketing eco-friendly automobiles is the grand challenge. Toyota frankly admits that nearly every aspect of this car's performance — fuel efficiency, passing acceleration, and emissions reduction — will have to be significantly better when Prius arrives here at the end of next year for any hope of success in the land of SUVs and dollar-a-gallon gasoline.