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Closed Loop Catalyst Temperature Feedback for Controlled Catalyst Lightoff and Diagnostics for ULEV
Technical Paper
1999-01-0311
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
There are three primary parameters that must be controlled in an engine for optimum performance; air, fuel (A/F ratio), and ignition (spark). Similarly, there are three primary parameters that must be controlled in a three-way catalyst for optimum performance; air, fuel (A/F ratio), and energy (temperature). Currently, most engine management systems provide closed loop control on the A/F ratio via oxygen sensor feedback, but temperature control is left to open loop methods with models and calculations. This paper will describe the benefits of closed loop catalyst temperature control (directly measured) for reducing emissions and providing a more robust catalyst monitor function. This catalyst monitor function will include measurement of catalyst lightoff performance which is the dominant effect causing HC tailpipe emissions to exceed OBD threshold levels. The lightoff measurement is not effected by driving cycle. This system is particularly applicable for ULEV systems applying small volume lightoff catalysts. Additionally, this work presents a system where the emission reduction system and the OBD catalyst monitor function are not in conflict with regard to optimum performance.
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Citation
Griffin, J., "Closed Loop Catalyst Temperature Feedback for Controlled Catalyst Lightoff and Diagnostics for ULEV," SAE Technical Paper 1999-01-0311, 1999, https://doi.org/10.4271/1999-01-0311.Also In
References
- SAE 981419 “Second Generation Platinum RTD Exhaust Gas Temperature Sensor for -50° C to 1000° C Measurement” Griffin et al
- SAE 982847 “Optimization of the Monitored Volume for LEV Catalyst Monitoring” Hepburn et al
- SAE 980674 “Engine-Out Tailpipe Emission Reduction Technologies of V-6 LEVs” Takahashi et al
- SAE 942058 “Catalytic Converter Diagnosis Using the Catalyst Exotherm” Theis
- SAE 932854 “Alternate Technologies for Studying Catalyst Behavior to Meet OBD II Requirements” Pelters et al
- SAE 980665 “OBD II Performance of Threeway Catalysts” Rieck et al
- SAE 980418 “The Development of BMW Catalyst Concepts for LEV/ULEV and EUIII and EUIV Legislations 6 Cylinder Engine with Close Coupled Catalyst” Otto et al
- SAE 980414 “The Conical Catalytic Converter and Its potential for Future Close Coupled Converter Concepts” Maus et al