Engine Performance and Exhaust Emissions: Methanol versus Isooctane

Operating characteristics of a single-cylinder, spark-ignition engine fueled by both methanol and isooctane were determined. Engine output, indicated specific fuel consumption, and specific emissions of hydrocarbon, carbon monoxide, nitric oxide, and aldehydes were measured for both fuels and compared using performance maps. The engine output comparisons showed that lean misfire limits occurred at leaner mixtures with methanol than with isooctane and that maximum engine output levels were nearly equal for both fuels. Comparison of the specific parameters of each fuel at equivalent power levels obtained with maximum power spark timing permits the following conclusions: Use of methanol results in higher indicated specific fuel consumption, greater emission of aldehydes, but lower emissions of hydrocarbon and nitric oxide; the two fuels showed similar trends of carbon monoxide emission.