%0 Conference Paper
%A Thomas P Wenzel
%A Marc Ross
%B International Fuels &  Lubricants Meeting &  ExpositionSAE Technical Paper Series
%C 400 Commonwealth Drive, Warrendale, PA, United States
%D 1998
%G eng
%I SAE International
%R 10.4271/981414
%T SAE Technical Paper Series Characterization of Recent-Model High-Emitting Automobiles
%U https://www.sae.org/content/981414/https://www.sae.org/gsdownload/?prodCd=981414
%V 1
%X <div>In-use vehicles which are high emitters make a large contributionto the emissions inventory. It is not known, however, whether high-emitting vehicles share common emissions characteristics. We study this by first examining</div><div>laboratory measurements of second-by-second engine-out and tailpipe emissions from a small number of</div><div>MY90-97 high-emitting vehicles. We distinguish highemitter types by the behavior of six ratios in low- and</div><div>moderate-power driving: the engine-out emissions indices (engine-out pollutant to fuel-rate ratios) and the catalyst</div><div>pass fractions (tailpipe to engine-out ratios) for CO, HC, and NOx. Four general types of high emitter are</div><div>observed: 1) fuel-air ratio excessively lean, 2) fuel-air ratio excessively rich, 3) partial combustion such as misfire,</div><div>and 4) severe deterioration in catalyst performance in vehicles where malfunctions of Types 1, 2 or 3 are not</div><div>predominant. We also find that these behaviors may be chronic, or may only occur transiently. The second step</div><div>is to determine the prevalence of the four different types of high emitter in the on-road fleet. For this we analyze</div><div>IM240 tailpipe emissions from a large sample of cars measured in the Arizona inspection and maintenance</div><div>program. We find that all four types of failure are observed with roughly comparable probabilities.</div>