Development of new 1.8-liter engine for hybrid vehicles

Abstract

In recent years, attention has been focused on a hybrid vehicle capable of substantial reductions in CO2 exhaust emissions. This paper describes the newly developed 1.8-liter 2ZR-FXE gasoline engine for use with a hybrid system for compact vehicles, which effectively combines higher driving performance with higher fuel efficiency. This engine was based on the 1.8-liter 2ZR-FE engine with outstanding performance and fuel efficiency. This engine has achieved high thermal efficiency by using the high-expansion ratio cycle "Atkinson cycle", as with the previous 1NZ-FXE engine. Additionally, a new cooled Exhaust Gas Recirculation (EGR) system and electric water pump were adopted to further improve fuel efficiency. A high efficiency cooler was used to cool the EGR gas, which enabled the introduction of the EGR gas at high load conditions, and exhaust gas temperature was reduced. As a result, this EGR system successfully combined both high output performance and low fuel consumption during high speeds. The electric water pump allowed the cooling water flow rate to be optimally controlled according to the engine operating conditions. This shortened engine warm-up time. In addition, friction was successfully reduced by eliminating accessory drive belts. With these improvements, lower fuel consumption has been achieved over the previous 1.5-liter 1NZ-FXE engine and, at the same time, the power output has been improved. Copyright © 2009 SAE International.