Toyota sets thermal efficiency goal

Toyota is looking at two concepts that will deliver petrol engines with more than 45% thermal efficiency in order to make its vehicles more economical to run.

The engines will be applied to future hybrid cars, according to Koichi Nakata of Toyota.

The Japanese carmaker hopes to improve on the engines of the first and second generation Prius, which have a thermal efficiency of around 37%, and the third generation Prius, which has a thermal efficiency of about 38%.

Toyota's aim is to achieve fuel efficiency of more than 40% with the Future Concept 1, and more than 45% with the Future Concept 2.

Some of the main technologies that the carmaker applied in the third generation Prius include the Atkinson Cycle with variable valve timing, cooled EGR, and lowered friction.

Concept 1 includes features such as a cooled EGR stoichiometric spark-ignited direct injection concept with a long stroke design and cooled EGR with an EGR ratio of more than 30%.

Meanwhile, Concept 2 is a turbocharged lean burn concept built around the same technology used in Concept 1 that also uses a long stroke design with a high tumble ratio.

According to Nakata, the engine team has already delivered 42.4% thermal efficiency in Concept 1 and 43.7% thermal efficiency in Concept 2.

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