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Two large, heavy light-duty gasoline vehicles (2004 model year Ford F-150 with a 5.4 liter V8 and GMC Yukon Denali with a 6.0 liter V8) were baselined for emission performance over the FTP driving cycle in their stock configurations. Advanced emission systems were designed for both vehicles employing advanced three-way catalysts, high cell density ceramic substrates, and advanced exhaust system components. These advanced emission systems were integrated on the test vehicles and characterized for low mileage emission performance on the FTP cycle using the vehicle's stock engine calibration and, in the case of the Denali, after modifying the vehicle's stock engine calibration for improved cold-start and hot-start emission performance.

In the last several years, there have been a number of independently run research programs evaluating the effects of electrically-heated catalysts (EHCs) on exhaust emissions from gasoline-fueled light-duty passenger vehicles. This paper “pools” data from several of these programs to determine the fleet effect by statistical methods. Evaluation of the overall data set from the eight car fleet indicates a very large reduction in total hydrocarbon (THC) and carbon monoxide (CO) but an accompanying increase (appreciably smaller in magnitude) in oxides of nitrogen (NOx). A follow-up program is under way to examine fuel sensitivity issues.

Improved designs of extruded metal electrically heated catalysts (EHC) in combination with a traditional converter achieved the California ultra-low emission vehicle (ULEV) standard utilizing 50% less electrical energy than previous prototypes. This energy reduction is largely achieved by reducing the mass of the EHC. In addition to energy reduction, the battery voltage is reduced from 24 volts to 12 volts, and the power is reduced from 12 kilowatts to 3 kilowatts. Also discussed is the impact EHC mass, EHC catalytic activity, and no EHC preheating has on non-methane hydrocarbon emissions, energy requirements, and power requirements.

A 1991 Toyota Camry equipped with an electrically-heated catalyst/light-off converter system was evaluated for emissions in duplicate over the light-duty Federal Test Procedure (FTP) with three different fuels. Evaluations were conducted with the electrically heated catalyst (EHC) in place, both without any external heating and with the EHC operated using a post-crank heating strategy The EHC system was placed immediately upstream of an original production catalyst which was located 40.6 cm from the exhaust manifold. The three test fuels were: 1) a fuel meeting California's Phase II gasoline specifications; 2) a low-sulfur (48 ppm) version of the Auto/Oil industry average gasoline; and 3) the Auto/Oil industry average gasoline, RF-A. On average, NMOG emissions and the ozone forming potential of the exhaust hydrocarbons exhibited the following trend for tests run in unheated and EHC-active modes: Phase II < low-sulfur RF-A < RF-A.

Low mass extruded electrically heated catalysts (EHC) followed directly by light-off and main converters resulted in non-methane hydrocarbon emissions (NMHC) between .020 and .023 g/mi at power levels as low as 1 kw and energy levels as low as 4 whr. These results were achieved on a 1993, 2.2 liter vehicle. The success of this system is due to rapid heat up of the catalyzed surface areas of both the heater and light-off converter. The energy added to the exhaust from both the heater and the light-off is then efficiently transferred to the main converter. In addition, the impact of power and energy on NMHC levels was determined. The Ultra-Low Emissions Vehicle (ULEV) standard was also achieved with uncatalyzed heaters and on a 1990, 3.8 L vehicle. The new California Low Emission Vehicle (LEV) and Ultra Low Emission Vehicle (ULEV) standards require a significant reduction in tail pipe emissions compared to current standards.

Low mass, extruded electrically heated catalysts (EHC) followed directly by a light-off and main converter reduced cold start non-methane hydrocarbons (NMHC) by greater than 80 percent. These reductions were demonstrated on several vehicle applications operating over the Light Duty Federal Test Procedure (FTP). To achieve this level of reduction, the design of the EHC cascade system, power level and heating time must be appropriately established. This paper discusses the impact of these design parameters on cold-start emissions reduction. From the test results, a generic empirical model was developed to predict EHC system conversion efficiency as a function of EHC power, heating time, and inlet exhaust temperature to the EHC.

Engine-aged EHC integrated cascades with equivalent overall volumes and several different design features were evaluated for FTP emission performance on a late-model V6 test vehicle. Design options evaluated included low and high cell densities (160 cpsi vs. 400 cpsi, a non-straight flow channel geometry (160 cpsi), and several low-power, zoned heating strategies (all with 160 cpsi). Cold-start hydrocarbon emission performance for the aged low cell density, high cell density, and non-straight channel designs (all with full face heating strategies) were found to be equivalent in the under-floor location used on the test vehicle in this program.