Toyota is bringing Atkinson-cycle technology, normally used in its dedicated hybrid engines, to mainstream vehicles as part of a new line of small gas engines.
Up to 14 new engine variations will be available by 2015 with two engines setting the foundations for the series. The first is a 1.3-liter 4-cylinder designed with a high 13.5:1 compression ratio that will utilize the Atkinson cycle. Toyota says it further improves the efficiency of the engine with a new intake-port shape that generates a strong tumble where the air-fuel mixture flows in the vertical swirl. Other features will include cooled EGR and variable valve timing. The end result is an engine with a maximum thermal efficiency of 38 percent, which according to Toyota, is the best among any mass-produced engine. Combined with start-stop and other fuel-saving features, the engine is expected to save up to 15 percent more fuel when compared to current vehicles.
The new 1.3-liter engine also features a 4-2-1 exhaust manifold to scavenge the cylinders quicker and friction-reducing technologies such as modified piston-skirt surfaces and plastic-coated bearings.
The other base engine for the series is a 1.0-liter jointly developed with Daihatsu. It achieved a 37 percent thermal efficiency with similar tumble-flow port designs, high 11.5:1 compression ratio and cooled EGR.