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Proof-of-concept testing was conducted to evaluate the ability to identify serious losses in catalyst efficiency with a dual oxygen sensor method. The dual oxygen sensor method involves a comparison between the signal from a pre-catalyst oxygen sensor to that from a post-catalyst sensor. Testing was conducted on a dynamometer test stand in an open-loop mode under steady-state conditions. Four matched catalysts and two deteriorated in-use catalysts were tested. The matched catalysts were identical in all physical characteristics, but with varying efficiencies. The operating air-fuel ratio was dynamically varied, and the test matrix included amplitude variations of the air-fuel ratio from 0.5% to 7% above and below the stoichiometric point, oscillating at three frequencies. Results from this proof-of-concept testing show measurable differences in the pre- and post-oxygen sensor signals between catalysts with good and poor conversion efficiencies.

An inexpensive system was designed that would allow repair shops to verify the adequacy of repairs made to cars that had previously failed the new high-tech I/M test (IM240). Before and after repair tests on a limited number of vehicles were performed with both official IM240 and prototype repair grade (RG240) equipment systems. Analyses were performed to determine if the RG240 system concept is capable of determining if the repairs performed resulted in adequate emissions reductions to assure a passing IM240 retest. This study focuses on development of a prototype RG240 system consisting of a 100 SCFM CVS, a dynamometer with an eddy current power absorber and non-adjustable 2000 pound inertia flywheel, and a BAR 90 emissions analyzer with an additional nitric oxide analyzer.