In 1993, Toyota decided to develop a green car. Its top management set a target fuel economy of 47.5 mpg, or about 50 percent better than the existing Corolla. Without specifying the means to do so, it was up to the R&D team to choose whatever technology. At first, engineers believed they could improve existing internal combustion engines and other areas of the car to meet the target. However, the management wanted a more radical solution that would take the company to the 21st century, so it lifted the target to 66 mpg, or 100 percent improvement. That was really a big challenge. Eventually, the development team chose the gasoline-electric hybrid power concept that had been explored by many pioneers before but all failed to bring it to commercial use. Thanks to unlimited resources supplied and the hardworking engineers, they overcame countless of technical hurdles, and the Prius went on sale in Japan just before the deadline set by the management. That was December 1997. For a technological breakthrough, its development time was incredibly short.
The original Prius was about as large as the contemporary Corolla, but its space-optimized shape gave it an interior matching a Camry while keeping weight pretty light at 1240 kg. The hybrid power system called THS (Toyota Hybrid System) had the engine, electric motor and gearbox mounted transversely and drove the front wheels just like a conventional FF car, thanks to its compact package. To enhance fuel efficiency, the engine was a 1.5-liter 16-valver running at Atkinson cycle (whose expansion stroke exceeds the compression stroke) and lower state of tune. It delivered only 58 hp. The AC electric motor produced another 40 horsepower. They were mated to a planetary gear set which doubled as a continuous variable transmission (CVT). Another electric motor, or more precisely a generator, was employed to generate electricity to supply the propulsion motor or to recharge the battery pack. The latter was mounted just behind the rear seat, consisted of 40 pieces of D-size Nickel-Metal Hydride (NiMH) cells. A very small fuel tank was placed under the rear seat cushion. As fuel consumption was only 50 percent that of a conventional car, its size was also halved. The packaging was so clever that it robbed little luggage space.
Judging by the standards of conventional cars, the Prius was inevitably slow, with a 0-60 mph time of 14 seconds and a top speed just shy of 100 mph, but the instant torque of its electric motor allowed it to drive with satisfying tractability in town. In congested cities like Tokyo or Hong Kong (which was one of the earliest to introduce it), its regenerative braking was especially useful to recharge its battery hence saving fuel. It started with electric power only and drove just as silent as an EV at low speed. The petrol engine joined at higher speeds to provide extra power. During cruising, the engine might turn off again if the motor was able to sustain that speed. Expectedly, its handling was crappy and it could be criticized for non-linear power transition and braking, but as the world's first production hybrid car its level of finishing was already very good. Toyota would improve it in 2000, boosting the power of both engine and motor and made the battery pack smaller and lighter by the use of custom cells.
The first generation Prius was immediately a hit in Japan. Its demand outstripped the original monthly production target of 1,000 units, so Toyota had to double its production. Further growth was fueled by its export to the USA since year 2000. Some 16,000 cars were sold over there in its first full year. By the time the Mk1 ended production in September 2003, an estimated 120,000 units had been built. This commercial success surprised many Western rivals which had never taken hybrid technology seriously. However, even then they had not realize the true potential...
In the following years, Toyota would improve the Prius relentlessly. The second generation had its power system refined a lot while its packaging was considerably enlarged to liberate more space. Now it was able to attract not only the extreme environmentalists but also average buyers who cared about practicality and costs. The third generation from 2009 improved on performance (thanks to a larger 1.8-liter engine), driver appeal and even further in fuel efficiency. These improvements reflected on sales: its global annual sales increased year by year, reaching 280,000 units in 2007, 400,000 units in 2009 and half a million units in 2010! No one could have predicted that it became the No.1 selling car in Japan and one of the most popular in the world as well. The Prius became an icon of green cars.
||Prius Mk1 (1997)||Prius Mk1 (2000)||Prius Mk2||Prius Mk3|
|Year of production
||120,000 units (Mk1)
||120,000 units (Mk1)||1.2 million units||est. 2.2 million units
||Front-engined, Fwd||Front-engined, Fwd||Front-engined, Fwd|
|Size (L / W / H / WB) mm
||4275 / 1695 / 1490 / 2550
||4310 / 1695 / 1490 / 2550
||4445 / 1725 / 1490 / 2700||4460 / 1745 / 1490 / 2700|
||Inline-4, dohc, 4v/cyl, Atkinson-cycle, AC motor.
||Inline-4, dohc, 4v/cyl, Atkinson-cycle, AC motor.||Inline-4, dohc, 4v/cyl, VVT, Atkinson-cycle, AC motor.||Inline-4, dohc, 4v/cyl, VVT, Atkinson-cycle, AC motor.|
||Engine: 58 hp
Motor: 40 hp
|Engine: 70 hp
Motor: 44 hp
|Engine: 76 hp
Motor: 67 hp
Combined: 108 hp
|Engine: 98 hp
Motor: 80 hp
Combined: 134 hp
||Engine: 75 lbft
Motor: 225 lbft
|Engine: 82 lbft
Motor: 258 lbft
|Engine: 85 lbft
Motor: 295 lbft
|Engine: 105 lbft
Motor: 153 lbft
||Planetary CVT||Planetary CVT||Planetary CVT|
||F: strut; R: torsion-beam
||F: strut; R: torsion-beam||F: strut; R: torsion-beam||F: strut; R: torsion-beam|
||105 mph||112 mph