Electrically Heated Catalysts and Reformulated Gasolines 930385
A 1991 Volvo model 960 equipped with an electrically heated catalytic converter system (EHC) was evaluated in multiple FTP tests with three different gasolines: current certification fuel, the Auto/Oil industry average fuel (RF-A), and a fuel that meets the 1996 California Phase II reformulated gasoline standards. Tests of each fuel were run with a low-mileage EHC located upstream of either a low-mileage stock main converter or a stock converter that had been road aged for 100,000 miles under European driving conditions. Test results with EHC operation showed significant variations in NMHC, CO, and NOX emissions with the three test fuels. NMHC emissions were 2-2.5 times lower for the Phase II fuel versus RF-A, with the certification fuel intermediate in NMHC emissions. Tests with the EHC/high-mileage converter system exhibited higher overall FTP emissions compared to the EHC/low-mileage main converter system, as expected. Fuel trends with respect to NMHC and CO were the same for both of these EHC/main converter systems. Expected differences in engine-out emissions for these three fuels, air/fuel stoichiometry during cold start-up, and the relatively cool exhaust temperatures during cold starts associated with this vehicle's underfloor converter system location contribute to the observed effects of fuel composition on emission performance.
