CRC sulfur/OBD-II laboratory research program executive and technical final reports

A laboratory research program was conducted to determine the relationship between fuel sulfur level, oxygen storage, capacity, and catalyst inefficiency in candidate LEV catalyst systems. The program was intended to determine whether technical justification exists for new malfunction indicator (MIL) illumination criteria, to accommodate the higher sulfur gasolines sold outside of California. Three candidate LEV and one production Transitional LEV(TLEV) catalyst systems were evaluated as a function of fuel sulfur level, catalyst aging, and air/fuel ratio for HC, CO, and NOX catalyst inefficiency, and at stoichiometric A/F ratio for three parametric measures of oxygen storage. The results obtained show that catalyst performance and oxygen storage capacity can be degraded with increasing sulfur levels from 40 to 1000 ppmS for all three constituents, and with catalyst aging at stoichiometric conditions, with some stronger effects observed at non-stoichiometric A/F ratios.