Toyota Debuts New 3- and 4-Cylinder Engines

Toyota Motor Corp. expects to achieve 10% better fuel economy with two new engines architectures that will spawn 14 variants over the next two years.

Toyota says the 14 iterations will power about 30% of its nameplates worldwide when they debut in late 2015.

The two designs a 1.0-liter 3-cylinder powerplant and a 1.4-liter 4-cylinder engine feature high compression ratios, reconfigured intake ports, expanded variable valve timing and a cooled exhaust gas recirculation system.

The larger engine employs an Atkinson combustion cycle. Toyota has used the system previously only in hybrid vehicles, where its characteristically lower torque can be offset as need by the powertrain's electric motor. Toyota says it has overcome the lower power issue by reducing internal friction, modifying intake gas flow to accelerate combustion, boosting the compression ratio to 14.0:1 and adding cooled EGR.

Toyota's new 3-cylinder engine, which was co-developed with affiliate Daihatsu Motor Co., uses similar techniques to improve efficiency. It operates with a compression ratio of 11.5:1.

The 3- and 4-cylinder engines achieve maximum thermal efficiency of 37% and 38%, respectively, compared with about 35% for the engines they will replace, according to Toyota. The company expects the two powerplants to boost fuel efficiency 15% and 30%, respectively, when coupled with an automatic stop-start system.