2010 Toyota Prius

Don Sherman

No shoes were flung when the 2010 Toyota Prius debuted at the recent Detroit auto show. Considering the grim mood in the Motor City - with domestic automakers on death watch and frozen credit paralyzing sales - and the fact that a gallon of gas costs little more than a can of beer, that's remarkable. Detroit was hardly the opportune place for a fuel-scrimping, technically advanced Asian import to bow. Then again, consider the Latin meaning of the word Prius: to go before. Defying skeptics is this car's cause. The Prius's mission has always been venturing ahead of the gas-saving, earth-hugging curve.

Toyota calls this the third generation of the Prius (not counting one sold in Japan from 1997 to 2000 but never imported here), but the gist of the world's best-selling gas-electric hybrid hasn't changed an iota. It rides on the same 106.3-inch wheelbase as its predecessor, and its external dimensions are longer, lower, and wider by smidgens. The fresh but still nerdy-looking skin smites the wind with a drag coefficient trimmed from 0.26 to 0.25. The front wheels are again energized by a compound powertrain consisting of one four-cylinder engine, two motor/generators, one planetary gearbox, and a nickel-metal-hydride battery pack.

The rumored plug-in lithium-ion batteries are a no-show for now, yet Toyota engineers overhauled the rest of the Prius's propulsion system. The DOHC sixteen-valve I-4 engine grows from 1.5 to 1.8 liters in displacement, upping peak output from 76 to 98 hp at 5200 rpm. One carryover feature is the use of the Atkinson cycle, a delayed intake-valve closing arrangement that yields a longer expansion stroke and reduced fuel consumption. The most notable engine innovation is the elimination of belts under the hood; all accessory equipment (A/C compressor, coolant pump, power-steering pump) is now directly driven by the engine or by an electric motor.

A new transaxle brings a 20 percent reduction in friction. About seventy pounds have been trimmed from the hybrid drive system. Gearing revisions supported by a 28 percent increase in peak engine torque (to 105 lb-ft at 4000 rpm) and a 22 percent gain in total hybrid system power deliver improved acceleration and better mileage. Expect an EPA combined rating of 50 mpg (versus 46 mpg for the outgoing Prius), with a city figure just over and highway mileage a bit under the nifty-fifty mark.

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