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Toyota Reveals Third-Generation Prius; 50 mpg
12 January 2009
|The 2010 Prius. Click to enlarge.|
Toyota Motor Sales (TMS), USA, unveiled the third-generation Prius hybrid vehicle at the 2009 North American International Auto show. The new version of the world’s top-selling hybrid vehicle (more than one million sold in 44 countries) offers better mileage ratings and enhanced performance, as well as new design features.
The first-generation Prius, which was EPA rated at 41 mpg US combined city/highway, was replaced by the current model, which is EPA rated at 46 mpg US, combined. Using a combination of technologies, fuel efficiency was increased to an estimated 50 mpg US combined for the new Prius.
Hybrid components like the inverter, motor, and generator are now smaller and lighter. An exhaust heat recovery system, exhaust gas recirculation, and an electric water pump contribute to a more efficient hybrid system with a net horsepower rating of 134.
The battery module carries over from the tried-and-true technology from the current Prius. Engineers applied enhancements throughout the entire vehicle to achieve 50 miles-per-gallon, more consistent efficiency in real-world driving, and further reductions in CO2 emissions.
Electric power consumption has been reduced through the use of a more efficient air conditioning system and new, optional LED head lamps. Internal tests show that Prius’ zero-to-sixty acceleration time has dropped from the previous generation’s mid 10-second range to 9.8 seconds, making it comparable to that of an average mid-size sedan with a 2.4-liter engine. This is in response to customer expectations for better every-day performance. In short, the entire Prius package has been made more efficient from overall power consumption to output.—Bob Carter, Toyota Division Group Vice President and General Manager
The new Prius also features what Toyota is calling a “Solar Moonroof”. A small array of photovoltaic cells automatically powers a ventilation system on hot days. The system allows fresh air to circulate into the vehicle, cooling down the cabin so that the air conditioning doesn’t have to work as hard, thereby conserving power.
|Preliminary 2010 Prius Powertrain Specs|
|Engine||1.8L I-4 with VVT-i|
|Engine power [hp (kW)]||98 (73)|
|Torque [lb-ft (Nm)]||105 (142)|
|Motor power [hp (kW)]||80 (60)|
|Motor torque [lb-ft (Nm)]||153 (207)|
|Net power [hp (kW)]||134 (100)|
|Emission rating||SULEV (w/ AT-PZEV)|
|Est. combined fuel economy||50 mpg US|
A larger and more powerful 1.8-liter Atkinson-cycle, four-cylinder engine powers the new Prius. The larger engine 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.
The patented Hybrid Synergy Drive system in the 2010 Prius is 90% newly-developed with significant improvements over previous models:
The transaxle is lighter in weight and reduces torque losses by as much as 20% 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% lighter.
A newly developed electronically controlled regenerative braking system has been adopted, with control logic optimized to enhance regeneration.
|Under the hood of the 2010 Prius. Click to enlarge.|
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 the best mileage.
Dimensionally, the new Prius has the same wheelbase as the current generation. Overall length is slightly increased by 0.6 inches, in part by moving the front cowl forward. Designers preserved the triangle form of the current model, but made alterations to the overall profile, pillar position and angle. The overall height of the Prius is the same, but the roof profile is altered by moving the top of the roof 3.9 inches to the rear. This emphasizes the wedge shape, and also allows for enhanced rear headroom and improved aerodynamics.
The new Prius received more wind tunnel hours of testing than any other Toyota vehicle yet. 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 next-generation Prius is built on a new platform, which enables improved handling stability, quieter operation, and collision safety. The suspension consists of front struts and a rear intermediate beam design, as before, but handling stability is advanced by improving the stabilizer layout, higher caster angle and tuning the bushing characteristics. Disc brakes are now used on all four corners, replacing the front disc/rear drum brakes in the current model.
Weight was saved through use of aluminum in the hood, rear hatch, front suspension axle and brake caliper and super high-tensile steel in the rocker inner, center pillar, and roof reinforcement. To meet customer expectations for everyday performance, zero-to-60 acceleration has been improved to 9.8 seconds, more than a second faster, in internal testing.
Better-performing sound insulation, working with improved vibration damping, has been installed in various locations to reduce road noise.
Toyota will use plant-derived, carbon-neutral plastics in the 2010 Prius. The newly-developed plastics, known as “ecological plastic,” will be used in the seat cushion foam, cowl side trim, inner and outer scuff plates, and deck trim cover. Ecological plastic emits less CO2 during a product lifecycle (from manufacturing to disposal) than plastic made solely from petroleum; it also helps reduce petroleum use.
Sales of the 2010 Prius will start simultaneously in both the US and Japan in late spring, followed shortly by Canada and other countries. Toyota forecasts first full calendar year sales in the US will be around 180,000 units.
We expect a large portion of this volume to come from current Prius owners. That’s because more than 90 percent say they will buy another Prius.—Bob Carter
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