Prius gets its power from a gasoline engine supplemented by an electric motor. In a bit of hyperbole, Toyota calls the combination the Hybrid Synergy Drive. Hybrid it is; synergistic it isn't, not by the strictest definition of the word, which would mean that the total power output would be more than the sum of the outputs of the gas and electric motors individually. This is not the case. The Hybrid Synergy Drive does, however, rely on the electric motor even more than the system in the first-generation Prius, which is how Toyota was able to make the Prius larger and more practical without compromising its low emissions or fuel economy. The current model is 30 percent cleaner than the squeaky-clean first-generation (2002-03) Prius. Toyota claims the 2005 Prius produces only a little more than 10 percent as much pollution as the average new car. Toyota says its hybrid system is an electric motor with gasoline engine assist, while Honda's system is a gasoline engine with electric motor assist.
By complementing the gasoline engine's horsepower with the electric motor's torque, the Prius makes better use of the energy stored in each gallon of gasoline, while leaving fewer nasty chemical compounds in its wake. The electric motor, which begins cranking out its maximum 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 at more constant speeds, especially during 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 you are waiting at a stop light or even when puttering around town at low speeds. Any time the driver's right foot requests more motivation than the electric motor alone can provide, the gasoline engine fires up and joins in.
The transmission is non-traditional, too, though not unique in today's market. Prius uses a continuously variable transmission, which shuns gears for a steel-segmented belt riding on variable-diameter pulleys. This system constantly and automatically selects the most efficient drive ratio to get the car moving and to keep it moving.
The EPA gives the Prius a City/Highway fuel economy rating of 60/51 mpg with a Combined rating of 55 mpg. These numbers have generated controversy, however. Hybrid-powered cars tend to achieve high ratings on EPA tests because the cars run on rollers, face no wind resistance, and run with the air conditioning shut off. The electric motor plays a bigger role in these laboratory conditions than it does in the real world. In one of those strange twists of logic often produced by law, Toyota is legally barred from advertising any mileage numbers other than those released by the federal government.
Most Prius owners report much lower fuel economy, while others argue this point. Published reports have pegged actual fuel economy at 44 to 48 mpg or 20-percent less than the government's EPA rating.
Emissions are the lowest of any real car available to U.S. buyers. On the surface, it is bettered by electric cars, but electric cars are impractical and must be recharged using another energy source that, in turn, requires fuel. So in the big picture, the Prius is easier on the environment than electric cars are.
The Prius saves fuel and reduces emisions by scavenging energy that most cars waste. Regenerative braking links the brakes to a generator, helping use the car's kinetic energy to recharge the battery whenever 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 Prius rides on regular, commonly available tires. They are not sporty treads, so don't look for quick and precise left-right transitions. But they are stickier than expected, and quieter than the earlier tires. Some tire noise is evident, no doubt because Toyota skipped some sound insulation in the interest of saving weight. But wind noise is nicely subdued by the car's impressive aerodynamics.
Braking is more linear than in the original model. New algorhithms in the computer that manages this system have made brake feedback more natural, so the brakes don't feel as obviously assisted and as if they were managed somewhere else. Tapping the dash-mounted shift lever to engage the B function (for engine braking) 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 soft rear suspension, compressing it to the point where occupants will feel the bump stops on mildly rough pavement. And this is without any luggage. The Prius is better with two adults and two kids. Next Page