New Prius has most thermally efficient gasoline engine

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Toyota has released technical details of its new fourth-generation Prius hybrid, which has a 1.8-liter gasoline engine that has achieved 40% thermal efficiency – a world best, says the Japanese OEM.

The motor is largely carried over from the previous model, but the retuned 2ZR-FXE unit in the 2016 Prius has had work carried out to reduce the friction of the rotating assembly and internal parts and improve combustion. The intake and exhaust systems have also been redeveloped to be quieter than before.

A new EGR system with cooler operates even at the engine’s maximum output to enable an ideal stoichiometric air/fuel ratio across the entire powerband, says Toyota. A smaller, lighter and quieter hybrid system water pump also does its part to reduce energy consumption.

The new car uses the heat from the EGR to speed engine coolant warm-up, which allows the hybrid system to stop the engine earlier and more often in the driving cycle when it’s not needed.

The Prius will be offered with the option of both a nickel metal hydride battery and a lithium-ion unit in the Japanese and US markets, while European cars will have to settle for the NiMH battery only. The NiMH battery pack is 10% smaller and holds 28% more energy than the current unit. The Li-ion pack is smaller still, by an estimated 15%, and significantly lighter, by 7.2kg.

Fuel consumption and emissions figures have yet to be officially confirmed, but Toyota is claiming that the European-spec Prius achieves 3 liters/100km (78.4mpg) on the NEDC and 72g/km CO2 emissions.

November 24, 2015

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Dean has been with UKi Media & Events for over a decade, having previously cut his journalistic teeth writing and editing for various automotive and engineering titles. He combines extensive knowledge of all things automotive with a passion for driving, and experience testing countless new vehicles, engines and technologies around the world. As well as his role as editor-in-chief across a range of UKi's media titles, he is also co-chair of the judging panel of the International Engine of the Year Awards.

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