The Prius' source of power is a conjoining of a gasoline engine and an electric motor. In a bit of hyperbole, Toyota calls the combination the Hybrid Synergy Drive. Hybrid it is; synergistic it isn't, not really. It earns the hybrid label by combining two, otherwise disparate, means of generating power to motivate a vehicle. To be synergistic, though, the resulting power output should total more than the sum of what the two systems produce when functioning independently. The hybrid system does not do this. But by complementing the internal combustion engine's horsepower with the electric motor's torque, it does make better use of the energy stored in each gallon of gasoline while leaving fewer nasties in its wake. The electric motor, which begins cranking out its torque virtually the moment it starts spinning, gets the car moving and helps it accelerate while it's underway. The gasoline engine steps to the fore in relatively constant and higher speeds, highway driving, where horsepower is more critical for maintaining a car's momentum.
The hybrid system improves fuel economy further by turning off the gasoline engine when it's not needed, like when the car's waiting at a stop light or even when putting around town at low speeds. Any time the driver's right foot requests more motivation than the electric motor alone can deliver, the gasoline engine instantaneously fires up and joins in.
The transmission is somewhat non-traditional, too. The Prius uses a continuously variable transmission, which constantly matches the most efficient drive ratio for the power output to get the car moving and to keep it moving.
The Prius scavenges as much as is possible of the kinetic energy contained in a car in motion, linking the brakes to a generator that recharges the battery when the brakes are applied. Along the same lines, the transmission offers a setting that helps recharge the battery when the driver merely lifts off the accelerator and lets the car coast, most beneficially downhill. In sum, with all these regenerative methodologies, there's no need (and no way, for that matter) to plug the car into an electrical outlet to charge the battery.
The 2004 Prius rides on regular, commonly available tires, versus the special, low rolling resistance tires on the 2003. They're not sporty treads, so don't look for quick and precise left-right transitions. But they are stickier than expected, and quieter than the '03's tires. Some tire noise is evident, though, no doubt in part due to the diet the designers put the Prius on in pursuit of those enviable fuel economy data. Wind noise is nicely subdued by the car's impressive aerodynamics.
Braking is more linear than in the 2003 model. That car was difficult to bring to a stop smoothly, as the regenerative system added braking effect beyond the direct control of the driver's foot. Some new algorhithms in the '04's computerized management system have made the brake feeling more natural, less obviously assisted and managed somewhere else. Tapping the dash-mounted shift lever to engage the B (engine braking) function returns a feel much like engine compression braking, as if the driver had dropped down a gear while slowing.
Four adults seem to be about the limit for the car's rear suspension, compressing it to the point occupants will feel the bump stops on mildly rough pavement. And this is without any luggage. Next Page