The first engine is a 1.3-liter unit that runs on the Atkinson cycle, which until now has been reserved for Toyota's hybrid powertrains. In fact, the automaker earlier this year announced it would employ the Atkinson cycle for the naturally aspirated 5.0-liter V-8 powering the upcoming2015Lexus RCF. As technical director Frank Markus stated in his report on the RC F, "the ideal Atkinson cycle captures and compress an amount of air that, when combusted and expanded throughout the entire power cycle, results in a cylinder pressure that's near atmospheric at the bottom of the piston's stroke, meaning the engine has wrung every bit of energy out of the fuel."

In addition to a high compression ratio of 13.5, Toyota's new 1.3-liter mill will feature an intake port shaped to generate a strong air-fuel flow that tumbles in a vertical swirl, a cooled exhaust gas recirculation system, and Variable Valve Timing-intelligent Electric (VVT-iE) technology. Toyota engineers combated engine knocking by placing water jacket spacers around the cylinders to control temperature and by increasing combustion chamber scavenging.

Other technologies include plastic-coated bearings, modified piston skirt surfaces, more efficient oil pump, and a stop-start system. In all, the 1.3-liter engine will achieve a thermal efficiency rating of 38-percent and a 15-percent increase in fuel efficiency compared to the engines it will replace.

Meanwhile, the second engine is a 1.0-liter unit that features many of the engineering tricks as the 1.3-liter mill. Its compression ratio, however, is slightly lower at 11.5 and Toyota rates its thermal efficiency at 37-percent, but it is estimated to be 30-percent more fuel efficient.That said, Toyota will attempt to improve the engines in itsfuture hybrid models, with a goal of increase the thermal efficiency in hybrid powerplants from 38.5 to 42 percent.

Source: Toyota