Search Results

A conventional automotive emission control system depends on the measurements provided by various sensors to control the air-fuel (A/F) ratio. Maintaining the A/F ratio close to stoichiometry permits catalytic converter to operate in an optimized efficiency, which reduces the exhaust emission. Malfunction resulted from engine misfire makes catalyst''s converting efficiency drop. Such a condition results in increased emissions as well as in damage to catalytic converters. So current researches are proceeded in response to the California OBD II (On-Board Diagnostics) and EOBD that will be adopted in Europe requirements for engine misfire detection in passenger vehicles. In this study, two methods to diagnose the misfire an approached: catalytic converter''s temperature measurement over the threshold exposure temperature to examine the catalyst''s damage, and the vehicle emission test over FTP-75 cycle by varying misfire rates.

This paper describes the development of a spark ignition engine operating in a stratified-EGR mode at part load. The concept is to reduce the pumping loss with high levels of EGR while maintaining stable combustion via charge stratification. Since the engine operates stoichiometrically, the ability to control NOx emissions by the three-way catalyst is retained. The configuration of introducing the stoichiometric fresh mixture to the center portion of the combustion chamber with the EGR gas on the two sides is visualized in a transparent engine using planar laser-induced fluorescence (PLIF) and Mie scattering. Visualization results showed that the stratification between air/fuel mixture and EGR gas was relatively well established during the intake stroke. There was, however, significant mixing in the late part of the compression stroke.