Toyota has recently launched a new downsized turbo unit – a 1.2-liter direct-injection turbocharged engine for the Japan-market Toyota Auris small car – as part of its worldwide engine upgrade of 14 high-efficiency powerplants through 2015. Toyota began to introduce its lineup of more frugal but more powerful engines last year.
It’s expected that by the end of the year, Toyota would have already rolled out 14 improved engines that cover around 30% of Toyota's global nameplates, which include the 2.0-liter turbocharged engine installed in the Lexus NX crossover. The company has also recently presented a new 1.5-liter naturally aspirated engine intended for the Corolla.
This range of engines offers fuel economy that’s at least 10% better than the current ones – a major aspect in Toyota’s goal to comply with increasingly stringent emissions standards. The automaker had prioritized gasoline-electric hybrid drivetrains over traditional internal combustion systems but the company is currently overhauling the base engines throughout the lineup.
Among the new technologies that Toyota has drawn on are direct injection, turbocharging, high compression ratios and lean-burning Atkinson-cycle combustion. To date, the company has released 8 of the 14 new engines.
Tetsu Yamada, general manager of engine design at Toyota's Unit Center powertrain development division, said that at least one of the new engines will attain a 40% thermal efficiency rate.
Furthermore, the 1.2-liter turbo produces a 36% thermal efficiency, compared with traditional turbo rates of between 30-35%. On the other hand, the new 1.5-liter direct-injection engine boasts a 38% turbo rate. In comparison, the Toyota Prius hybrid is powered by the ultraefficient engine that can achieve thermal efficiency of 37%.
Thermal efficiency measures how much engine power is lost through heat - a higher rate is better. According to engineers, the new 1.2-liter turbo will offer better fuel economy than the 1.8-liter engine also available in the Auris while producing a more powerful low-end torque. The Japan-made Auris hatchback will be offered in the U.S. as the Scion iM this September.
However, the U.S. version will only be available with the 1.8-liter engine. Toyota is in the process of looking at the demand in the U.S. for downsized turbos, according to Shinichi Yasui, executive chief engineer for Corolla-class vehicles.
He said that Americans have a preference for bigger displacement, naturally aspirated engines. Competitors like Honda Motor Co. and Mazda Motor Corp. are overhauling their own engine lineups too.
Direct-injection technology and turbocharging are what Honda’s range of Earth Dreams engines are utilizing. Meanwhile, the updated Skyactiv engines of Mazda make use of fuel injection with ultrahigh combustion ratios.