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Methanol, a popular alternative fuel candidate, can theoretically be dissociated on-board a vehicle into a 2/1 molar mixture of hydrogen (H2) and carbon monoxide (CO) having a 14 percent greater heating value than that of methanol vapor. In this study, engine efficiency and fuel consumption with methanol vapor and dissociated methanol (simulated by a 2/1 mixture of Ha and CO) were compared in a single-cylinder engine at equivalence ratios (Φ’s) ranging from 0.5 to 0.9 and compression ratios (CR’s) from 11 to 14. Whan compared at the same Φ and CR, the reduction in fuel consumption for dissociated methanol compared to methanol (3-7 percent) was smaller than would be expected based on heating value alone. Indicated thermal efficiency with dissociated methanol was only 0.89-0.55 times that with methanol. Thermodynamic analyses were conducted to isolate the factors responsible for lower efficiency with dissociated methanol.

An engine dynamometer test procedure was developed for evaluating fuel and fuel additive effects on the plugging of port fuel injectors. The test procedure was shown to adequately reflect the influence of fuels and additives on injector plugging in vehicles. Injector soak temperature and fuel system configuration were found to be critical factors in obtaining an acceptable engine-vehicle correlation. Injector plugging occurred in as little as 10 hours with a high-olefin base fuel; in contrast, plugging took two orders of magnitude longer with a high-quality, detergent-containing, commercial-type fuel. Furthermore, fuel additives greatly increased plugging resistance with the OEM, pintle-type injectors. Injector design alterations were also shown to be important. Pintle-type injectors with flared, aluminum caps extended plugging time considerably relative to the same injector design with plastic caps. Director plate-type injectors were much better still.