Friction wastes energy in the form of heat energy. The Prius engineers were able to reduce the amount of friction by 26.8% from the Gen II.
General Improvements
In order to produce a 10% mileage improvement (45 -> 50mpg) the Prius engineers had to review every aspect of the car and find ways to improve upon them. This chart provides an overview of how each component has been improved from the Gen II to the Gen III.
Even though the high voltage battery pack is the same as the Gen II, the High Voltage system overall has been improved by 23%.
It sounds counter-intuitive, but the larger engine actually improves efficiency. The larger engine does not need to work as hard to propel the car. And when at cruising speeds, the engine does not work as hard to maintain speed.
Reduction of Mechanical Friction Loss
Friction wastes energy in the form of heat energy. The Prius engineers were able to reduce the amount of friction by 26.8% from the Gen II.
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Highway Speed Improvements
With the increased engine size of the 2010 Prius, highway driving is a little easier. This is because the 1.8 liter engine doesn't have to work as hard at highway speeds than the previous model's 1.5 liter engine. As you can see from the chart on the right, the greatest improvement is realized at speeds near 60 miles per hour. Keep in mind that this chart is a relative comparison and does not indicate that the best highway speeds are at 60mph. |
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Sources
www.fueleconomy.org
http://www.carseek.com/reviews/toyota/2010-prius/
http://en.wikipedia.org/wiki/Toyota_Prius
Toyota documents we're not supposed to disclose