Toyota announced today that it is working on a new generation of highly fuel-efficient engines that will be introduced globally by 2015. A total of 14 new engine variations will be used in models scheduled for partial redesign in the near future, with their most important quality being the “outstanding thermal efficiency,” according to Toyota.
Thermal efficiency shows how much of the thermal energy generated by burning fuel is converted into effective power: the higher the thermal efficiency, the lower the fuel consumption. The new engines benefit from combustion and loss-reduction technologies perfected by Toyota in its dedicated hybrid engines, with the carmaker saying they will be at least 10 percent more fuel-efficient over the units they will replace.
One of the engines is a 1.3-liter gasoline engine in which Toyota is employing the Atkinson cycle, normally used in dedicated hybrid engines. Use of the Atkinson cycle provides an increased expansion ratio and reduces waste heat through a high compression ratio (13.5), resulting in superior thermal efficiency.
Toyota aims to further improve the fuel efficiency of the engine by utilizing other innovations including an intake port with a new shape that generates a strong tumble flow (whereby the air-fuel mixture flows in a vertical swirl) inside the cylinder, and a cooled exhaust gas recirculation (EGR) system paired with Variable Valve Timing-intelligent Electric (VVT-iE) technology to improve combustion and reduce loss.
Toyota says the new engine will have a maximum thermal efficiency of 38 percent, top-level among mass-produced engines. The engine will thus be approximately 15 percent more economical compared with current vehicles.
The automaker has also developed a 1.0-liter gasoline engine with Daihatsu, which has achieved a maximum thermal efficiency of 37 percent due to a similar tumble flow-generating intake port, a cooled EGR system, and a high compression ratio. Vehicles that will use this engine will achieve a maximum fuel efficiency improvement of approximately 30 percent over current vehicles, Toyota says.
By Dan Mihalascu
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