Abstract
A new 1.5 liter 4-valve DOHC lean-burn engine with the innovative, wider air/fuel range three way catalyst has been developed in order to improve fuel economy. This paper describes the state-of-the-art combustion technologies which enhance combustion stability in order to improve thermal efficiency during lean burn operations, a newly-developed three way catalyst which significantly reduces NOx emission in the lean burn exhaust gas, and an engine management system which improves drivability under all conditions dramatically. By these technologies, the lean burn operation range has been increased to achieved substantial improvement of fuel economy. The fine turned "Z-LEAN" engine realized improvement of 16% with a manual transmission and of 10% with an automatic transmission for the car with an inertia weight of 1250kg compared with that with a normal engine under Japanese 10-15 mode cycle.