The philosophy behind the Prius' development was to maximize energy savings at every opportunity. By combining a gasoline engine, a battery and electric motor, and sophisticated power management, the Toyota Hybrid System can deliver significantly better fuel efficiency than vehicles with comparably sized gasoline engines. Here’s how the pieces come together:
In everyday driving, a conventional engine cycles through an efficiency curve in each gear. If engine speed is too low, fuel efficiency suffers. Similarly, if
engine speed is too high, the engine consumes fuel too quickly. The best fuel efficiency is attained at a sustained engine speed, as in long-distance highway cruising. In the Toyota Hybrid System, a custom-built engine produces a single high-efficiency power curve, and cycles from 1,000rpm to roughly 4,000rpm. In situations where the engine would drop below 1,000rpm, it shuts off; adequate power in this range can be more efficiently supplied by the battery. Likewise, when power requirements exceed what the engine can produce at higher revolutions, the battery kicks in with additional power.
the Prius takes part in an exhibition at the Museum of Modern Art in New York City in summer 1999.
Making the Most of Motive Force