May 20, 2009. Copyright 2009, Graphic News. All rights reserved

Toyota Prius III hybrid -- more power and even better fuel economy
By Neil Winton

LONDON, May 20, Graphic News: Toyota’s Prius has been successful probably beyond the Japanese company’s wildest dreams.

The world’s first hybrid car -- powered by two engines, one conventional petrol, the other an electric motor -- not only notched up huge sales, but also captured the imagination of green activists and Hollywood celebrities for providing transport that was convenient and practical, but kind to the environment because of its “amazing” fuel economy.

However, that green reputation has been questioned. Firstly, the fuel economy claimed by Toyota -- an average of about 65.7mpg-4.3 litres per 100km -- proved very difficult to reach in the real world of highway and city driving. Most Prius users would probably manage about 42mpg-6.7-l/100km. This compared less than favourably with a conventional diesel-powered 2.0 litre car, which could produce better fuel efficiency and provide more power.

There were also questions about the recyclability of the batteries, and worries about residual values because of doubts about the life of the high-tech electric components.

Toyota said that because of the relatively small 1.5 litre engine in the Mark II Prius, fuel economy on the highway was perhaps not as good as it should be because the motor had to strain to keep up high cruising speeds.

Toyota has addressed some of those criticisms with the new Mark III Prius.

The hybrid’s overall power has been increased by 22 percent to 134bhp with the adoption of a 1.8 litre “Atkinson cycle” engine. Atkinson cycle engines raise efficiency by improving the valve function in an internal combustion engine. Fuel economy has been increased by 10 percent with Toyota now claiming the Prius will achieve 72.4mpg-3.9-l/100km, and Carbon Dioxide (CO2) emissions down 14 percent to 89g/km.

The Prius engine is a “strong” hybrid compared with the Honda Insight hybrid’s “mild” system. This means that the electric motor in the Prius can power the car independently. Mild hybrids just help the petrol engine and can’t act independently. The Prius II could achieve about one or two miles of electric-only operation. The new one is better “with the car’s driving range determined by the level of battery charge” said Toyota, without elaborating.

The new Prius uses a nickel-metal hydride battery linked to an 80bhp (60kW) electric motor 20 percent more powerful than the old one, and 33 percent smaller. When the Prius is virtually freewheeling down inclines excess energy is captured and diverted to the battery via the so-called regenerative braking process. This is then returned to boost the petrol engine’s power.

The benefit of hybrid-power might be controversial, but the next generation is likely to give electric cars a decisive advantage. Toyota has announced that it will lease 150 experimental Plug-in Hybrid Vehicles (PHVs) in Europe in late 2009. Toyota’s PHV uses the latest lithium-ion batteries to allow extended battery-only operation, which can be recharged by the on-board petrol engine to allow a huge range. Unlike the Prius, PHVs can also be recharged from the domestic electricity supply. Toyota wouldn’t say what the battery-only range would be. General Motors hopes to launch its PHV, the Chevrolet Volt, late next year, claiming about a 50-mile electric only range.
/ENDS