Toyota Prius
The
Toyota Prius is one of world's first commercially mass-produced
hybrid automobiless. Manufactured by
Toyota, the Prius first went on sale in
Japan in
1997. Since then, there have been over 120,000 units sold in Japan,
Europe, and
North America as of September,
2003. Prius (2000~2003 model years) is certified as a super ultra low emission vehicle (SULEV) by the
California Air Resources Board (CARB).
The Prius has been called a true hybrid vehicle, designed from the bottom up. Toyota's goal for the Prius is to reduce the amount of emissions it produces and to be as energy-efficient as possible. They used several methods to try to achieve this goal, including:
- More efficient use of internal combustion engine (ICE) and electric motors, reducing gasoline consumption;
- Lower coefficient of drag at 0.29, reducing air resistance especially at higher speeds;
- Lower rolling-resistance tires, reducing road friction;
- Regenerative braking, a process for recovering kinetic energy when braking or traveling down a slope and storing it as electrical energy in the traction battery (a rechargeable nickel metal hydride (NiMH) battery) for later use while reducing wear and tear on the brake pads;
- Continuously variable transmission. Actually, the gear ratios are fixed; i.e. one can accelerate from zero to the maximum speed in one gear. The two electric motors and the ICE are engaged in a planetary gear arrangement.
- Flexible resin gas tank, reducing the amount of hydrocarbon emissions in the form of escaped gasoline vapour.
Touted advantages of the Prius over previous energy-efficient designs include in never needing to be plugged in, all power being delivered ultimately from the gasoline engine. This means it drives like a traditional ICE automobile, the onboard computer in the Prius taking care of shifting power to and from the engine and motors, automatically determining the most efficient use of the engine or the electric motors (or both) based on driving conditions, and when to charge the battery.
The engine is permitted to shut down once the engine has warmed up and the catalytic converter in the exhaust system has reached operating temperature. Once this occurs, the Prius can be driven on electric power only; this is sometimes referred to as "stealth mode". This further reduces gasoline consumption and wear and tear on the engine. When driving conditions demand additional power from the engine, it is designed to start up automatically.
Frequent starting up and shutting down of the engine should not cause additional wear and tear, as in conventional automobiles, because the drive motors have enough power to quickly and smoothly spin the engine to optimal RPMs (around 1,000) before the engine actually begins to "fire up". This avoids wear when the engine is "running" (with fuel and spark) at very low RPM, as happens in most vehicles.
2004 Prius
The Prius 2004 model year is a complete redesign of the previous generations of Prius. With a new drag coefficient of 0.26 and featuring the third generation hybrid powertrain technology called Hybrid Synergy Drive (HSD), the new 2004 Prius has more room (4 doors plus a rear hatch, a smaller but more powerful NiMH battery), is more powerful (2 seconds faster in 0 km/h to 96 km/h acceleration) and 15% more fuel efficient than the previous generation Prius (59 mpg city, 51 mpg highway), yet is still 90% cleaner than conventional gasoline-only automobiles. It comes with an Advanced Technology Partial Zero Emission Vehicle (AT-PZEV) certification by CARB. As an interesting side note, the 2004 Prius has the ability to park itself with onboard sensors to detect obstructions.
Notable Facts
- Drivers of the Toyota Prius, or other Hybrid-Engine automobiles are allowed to drive by themselves in Carpool (High Occupancy Vehicle) lanes in some US states such as Virginia, California (pending) and Florida (requires $5 per year decal).
- Due to the success of both the engineering and sales of the Prius, Toyota is currently planning a hybrid V-6 engine for the Lexus GX, as well as a hybrid engine version of the Camry. Toyota plans to sell the Lexus in late 2004, promising equal performance of the 4.7L V-8 currently shipping in the GX470, with the fuel economy of the Camry's 2.2L 4-cylander engine.
- Toyota is also actively developing a hydrogen-fuel-cell engine. They have already successfully developed a RAV4 that can achieve 900 miles on one tank of hydrogen.
Other Hybrid-Engine vehicles
- Honda Civic hybrid, another car which works similarly
- Honda Insight, a 2 seater hybrid car which Honda claims can get 58 miles per gallon.
- Ford is planning a hybrid engine version of the Escape.
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