Among the R&D projects Toyota Motor is exploring to further lower fuel consumption and emissions are two concepts on a pathway to deliver gasoline engines featuring more than 45% thermal efficiency for application in its future hybrid vehicles, according to Koichi Nakata of Toyota in his presentation today at SAE 2011 High Efficiency IC Engines Symposium in Detroit.

The engine used in the first- and second-generation Prius (the 1.5L 1NZ-FXE) had a thermal efficiency of about 37%; the thermal efficiency of the new 1.8L unit in the third-generation Prius (2ZR-FXE) has a thermal efficiency of about 38%. Toyota is targeting a thermal efficiency of more than 40% with what Nakata called its Future Concept 1, followed by thermal efficiency of more than 45% in Future Concept 2 (which is based on concept 1).

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