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Recent changes in regulatory practices have brought about a need for speciated analysis of the volatile organic components of vehicle exhaust. The purpose of this study was to allow interested laboratories to participate in a Round Robin so that each could assess its speciation methodologies for hydrocarbons, alcohols, and carbonyls. The results from analysis of the liquid samples (methanol, ethanol, and DNPH-derivatives of carbonyls) were reported in SAE 941944. For gaseous hydrocarbon samples, two gasolines from the Auto/Oil Air Quality Improvement Research Program (AQIRP) were used to prepare compressed gas cylinders of “synthetic exhaust.” These samples were also doped with typical light hydrocarbon combustion components, marker compounds, and MTBE (in one of the two sets of samples). The cylinders were circulated to 16 laboratories, which included automotive and petroleum companies, contract laboratories, and regulatory agencies.

In 1992, a Round Robin was sponsored by the CRC's Emissions Analysis Round Robin Subcommittee, to provide an opportunity for automotive emissions laboratories to compare their analytical methodologies with those used in other laboratories. Compressed gas samples were provided to participants to test hydrocarbon methodologies, while liquid samples were used for alcohol and carbonyl analyses. The results of this study were published in SAE 950780 and SAE 941944. A second Round Robin study was conducted in 1995, using the same basic structure as the first study. The results of the carbonyl analyses have been published separately (SAE 971609). The purpose of this paper is to compare methods used for hydrocarbon speciation of emissions by gas chromatography. As in the 1992 study, cylinders of a synthetic exhaust were prepared by using a fuel base, and adding components that would be expected as typical combustion products.

The Coordinating Research Council, Inc. has studied the octane requirement increase (ORI) of cars and light duty trucks since 1971. This paper investigates ORI trends and influencing effects for over 600 1980 through 1988 model-year vehicles. An analysis of these vehicles shows them to have an average ORI of 3.8 (R+M)/2 measured with refinery-like fuels, and suggests the average ORI decreased from 1980 through 1986, followed by a possible, but statistically uncertain, increase starting in 1987 or 1988. A number of factors have contributed to lower ORI, including higher compression ratios, use of aluminum cylinder heads, multiport fuel injection, and three-way catalyst systems. SPARK KNOCK IS THE NOISE produced by the auto-ignition of the air-fuel mixture in the end gases of the spark-ignition engine.