The effect on exhaust gas emissions (carbon monoxide, CO, hydrocarbons, HC, and aldehydes, CHO) resulting from mixing methanol and/or ethanol with gasoline for automotive fuels has been studied experimentally. Tests were conducted on an OEM four-cylinder engine running at different conditions of equivalence ratio and spark timing. Fuel blends with different percentages of alcohol content and different ratios of methanol to ethanol in the alcohol mixture were tested. Results of this investigation indicated that the presence of either or both of the alcohols in fuel blends significantly reduced the concentration of carbon monoxide in the exhaust emissions (up to 40–50 percent compared to pure gasoline only), with methanol slightly more effective than ethanol. Hydrocarbon emissions were also decreased by increasing the alcohol content of the fuel, with minimum hydrocarbon production occurring at percent alcohol-gasoline blends in conjunction with near-stoichiometric air-fuel ratios. However, aldehyde emissions were found to be markedly higher with alcohol-gasoline blends. The 10 percent alcohol-gasoline blends were found to produce about 50 percent more aldehyde emissions than pure gasoline.

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