Today, Toyota introduced a new generation of highly efficient engines. The professional Toyota-watcher was not surprised, after all, Toyota’s Takeshi Uchiyamada (now Chairman) said two years ago that they would be coming, and here they are. The interesting part is that they are conventional gasoline engines. The really interesting part was a chart that showed gasoline power-trains being as efficient as hybrids, and both being trumped by the diesel engine. The sky did not part, and no lightning struck the Toyota engineers who put up the chart.
Car engines are quite generous when they handle fuel. Only about a third of the energy is converted into motion. Most of the energy is given back to earth in form of heat and greenhouse gases. The engineer calls that thermal (in-)efficiency. Conventional gasoline engines have a thermal efficiency of around 35 percent. Toyota’s hybrid technology raised the thermal efficiency by a few points to 38.5 percent.
Quite interestingly, Toyota did not improve on the hybrid powertrain in this round of development. Toyota engineers improved the efficiency of the trusted old gasoline engine.
Toyota went the same route as Mazda, namely raising the compression ratio. While Mazda goes as high as 14:1 in their new Skyactiv engine, Toyota stopped at 13.5:1. As Mazda found out, raising the compression ratio also invites engine knock. Toyota beats engine knock with three measures:
New intake ports create a vertical air-fuel swirl, resulting in rapid combustion before knocking can occur. The combustion chamber is cleared of gases before a new fuel-air mix is introduced. A water jacket around the cylinder keeps temperatures in check. Toyota engineers said today that their solution is superior to that of Mazda.
With this technology, Toyota could raise thermal efficiency to 38 percent, bringing the gasoline engine very close to the 38.5 percent of the Prius.
Toyota announced two engines today, a 1 liter, and a 1.3 liter mill. 14 variants will be introduced by 2015, including fuel injected and diesel models.
Toyota aims at raising thermal efficiency to 40 percent and beyond. As Uchiyamada hinted two years ago, and as Toyota engineers suggested again today, diesel will play an increasingly important role in this endeavor.
In today’s presentation, Toyota wasn’t shy to show that a gasoline engine can be as efficient as the hybrid, with room for further improvement. And that was the big announcement of the day.