Integration of Engine Controls, Exhaust Components and Advanced Catalytic Converters for ULEV and SULEV Applications

Development of integrated engine controls, exhaust components and advanced catalytic converters was demonstrated on a 1998 full size luxury sedan with a gasoline PFI 4.4 L V8 engine. This level of emissions management was targeted for ULEV and SULEV emission standards. An air gap, dual exhaust, six-catalyst system, was modified in stages to reduce the number of catalysts and associated controls/hardware. Engine controls and calibration were developed to reduce cold-start emissions, catalyst light-off time and tailpipe emissions. Systems integration involved reduced precious metal loading, secondary AIR and modification of emission control devices. The thermal mass of the air gap exhaust pipes was reduced by approximately 30 percent, which contributed to improved catalyst heat-up time. A vacuum-insulated catalytic converter with phase change material was used to store exhaust heat and resist heat loss during times of dwell/soak. FTP-75 tests typically included two LA4 preparation cycles prior to soak. Upon engine start, the catalyst was at an elevated temperature, thereby reducing cold-start emissions. Catalyst start temperatures, which are a function of prep cycle and soak times, were studied.