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This paper presents the results of a twenty- vehicle program designed to determine the functional relationship between intake valve deposit level and exhaust emissions. The “identical” 1990 model year vehicles used for this program had accumulated over 80,000 kilometers in taxi fleet service and had developed average intake valve deposit levels which ranged from 6 to 9 on the Coordinating Research Council merit scale. The exhaust emissions from these vehicles were measured in triplicate tests using the 1975 Federal Test Procedure. The intake valve deposits were then mechanically cleaned in-situ, and exhaust emissions were again measured in triplicate. Special procedures were followed to minimize vehicle-to- vehicle variability and to obtain statistically meaning ful results. Results showed intake valve deposits to have a significant adverse effect on exhaust emissions.

An Oldsmobile 5.7 ℓ V-8 Diesel engine was fumigated with methanol in amounts up to 40% of the fuel energy. The primary objectives of this study were to determine the effect of methanol fumigation on fuel efficiency, smoke, nitric oxide emission, and the occurrence of severe knock. An assessment of the biological activity for samples of the raw exhaust particulate and its soluable organic extract was also made using both the Ames Salmonella typhimurium test and the Bacillus subtilis Comptest. Results are presented for a test matrix consisting of twelve steady state operating conditions chosen to reflect over-the-road operation of a Diesel engine powered automobile. Generally methanol fumigation was found to decrease NO emission for all conditions, to have a slight effect on smoke opacity, and to have a beneficial effect on fuel efficiency at higher loads. Also at higher loads the methanol was found to induce what was defined as “knock limited” operation.