Automotive Intelligence - the web for automotive professionals and car enthusiasts
January 13, 2009
A larger and more powerful 1.8-liter Atkinson-cycle, four-cylinder engine will power the new Prius. Contrary to conventional wisdom, the larger engine actually helps improve highway mileage. By making more torque, the new engine can run at lower average rpm on the highway. When operating at lower rpm, the new engine uses less fuel. Mileage is especially improved in cold-start conditions and at higher speeds.
Use of an electric water pump and a new exhaust gas recirculation (EGR) system also contribute to the engine’s efficiency. The 1.8-liter Prius engine is the first Toyota power plant that requires no belts under the hood for better fuel economy and less potential maintenance.
A multi-information display panel that monitors fuel and energy consumption is standard. It provides feedback on the Prius’ efficiency using three different displays to help the driver acquire economical driving habits.
Unlike most other hybrid vehicles available, Prius has been a “full” hybrid since introduction. This allows it to run on engine alone, battery alone, or a combination of both. The system blends the best of parallel hybrid and series hybrid designs to achieve the ability to operate on the electric mode alone, and to charge the batteries while the car is running.
The patented Hybrid Synergy Drive system in the 2010 Prius is 90 percent newly-developed with significant improvements over previous models. The transaxle is lighter in weight and reduces torque losses by as much as 20 percent compared to the previous model. The inverter, which converts direct current to alternating current, has a new direct cooling system to reduce size and weight. Taken together, the inverter, motor and transaxle are smaller and 20 percent lighter. A newly developed electronically controlled regenerative braking system has been adopted, with control logic optimized to enhance regeneration. The new Prius will offer three alternative driving modes. EV-Drive Mode allows driving on battery power alone at low speeds for about a mile, if conditions permit. There is also a Power Mode, which increases sensitivity to throttle input for a sportier feel, and an Eco Mode, which helps the driver achieve their best mileage.
World’s Lowest Cd
The new Prius received more wind tunnel hours of testing than any other Toyota in history, resulting in the cleanest aerodynamic profile of any mass-produced vehicle in the world. By focusing on the shape of the body, underfloor, wheelhouse liner and shape of the wheels, the designers of the new Prius were able to reduce the coefficient of drag (Cd) value to 0.25, compared to 0.26 for the previous model. The airflow under the car was studied extensively. Engineers made changes to the shape of the fender liner, front surface of the underfloor, and added a fin at the rear floor cover to increase linear stability.
The development of the Prius has required applications for over 1,000 patents filed across the world, of which 292 are U.S. applications.
Pricing for the 2010 Prius will be announced shortly before it goes on sale late spring.
(January 12, 2009)