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Understanding Sulfur Interaction Key to OBD of Low Emission Vehicles
Technical Paper
2000-01-2929
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
As the automobiles move closer to the ULEV, ULEV-2 and SULEV requirements, OBD (on board diagnostic) will become a design challenge. The present OBD II designs involve the use of dual oxygen sensors to monitor the hydrocarbon performance of the catalytic converter. The aim of this study was twofold:
- to determine the interaction of fuel sulfur and ceria in the catalyst formulation on the performance of a Pd/Rh TWC (three-way catalyst)
- to elucidate the sulfur and ceria interaction on the ability of the Pd/Rh catalyst to monitor the state of the catalyst relative to hydrocarbon activity and therefore it's utility in the OBD system.
Catalyst samples were aged on a spark ignited engine using a “fuel cut” engine aging cycle operated for 50 hours. Maximum catalyst temperatures during this aging cycle were 850-870°C. The effect of sulfur was determined by measuring aged catalyst performance using both indolene (∼100 ppm sulfur) and premium unleaded gasoline (∼350 ppm sulfur). The test for OBD performance was an oxygen storage capacity determination. The delay time between a front and a rear oxygen sensor was measured, as the engine was transitioned from a rich operating mode to a lean operating mode.
This study showed that higher levels of fuel sulfur were associated with longer OBD delay times for both fresh and engine-aged catalysts, and that introduction of high fuel sulfur gasoline can cause errors in an OBD calibration algorithm developed for use with a low sulfur content gasoline.
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Tauster, S., Rabinowitz, H., and Heck, R., "Understanding Sulfur Interaction Key to OBD of Low Emission Vehicles," SAE Technical Paper 2000-01-2929, 2000, https://doi.org/10.4271/2000-01-2929.Also In
References
- Rabinowitz, H. Tauster, S. Heck, R. The Effects of Sulfur & Ceria on the Activity of Automotive Pd/Rh Catalysts, Special issue of Applied Catalysis A: General
- Hepburn, J. Dobson, D. Hubbard, C. Goldberg, S. Thanasiu, E. Watkins, W. Burns, B. Gandhi, H. A Review of the Dual EGO Sensor Method for OBD-II Catalyst Efficiency Monitoring SAE 942057 October 1994