An Electronic Control System for Exhaust Emissions and Fuel Economy of Quasi-Homogenous Lean Burn Gasoline Engines

An adsorber-reduction catalyst system has been developed for NOx emission control on a lean burn gasoline engine. Its electronic control system can provide different time intervals and variable A/F ratio at lean mode and rich mode. In storage mode, the engine operates at lean burn under rich oxygen environment. In reduction mode, ECU turns down both the throttle angle and ignition timing to provide a stable torque output. This electronic control system is used to investigate the impact of engine speed and load on emission characteristics and fuel economy. It is indicated from experimental results that the upstream placement of TWC (three way catalyst) ahead of the designed NOx adsorber catalyst gives rise to highest converting efficiency to reduce the NOx emission level. The roles of engine speed on exhaust emissions and fuel economy are reflected by operating time of lean burn and rich burn as well as the time ratio between the two regarding this designed catalyst converter. Engine load acts as a major factor in affecting exhaust emission characteristics and fuel economy of the lean burn engine. The heavier the engine load, the higher the NOx emission level, the less the NOx conversion rate, the better fuel economy.