Demonstration of Fuel Economy Potential of M-85
Shean Patrick Huff


     Abstract: A stock gasoline was converted to operate on M-85 (a mixture of 85% methanol and 15% gasoline by volume and concepts were used to increase the vehicle’s fuel economy was implemented to improve the conversion.

     Under the normal circumstances, a simple conversion of an engine from gasoline to methanol operation results in an increase in power-related performance. This increase is due to methanol’s high latent heat of vaporization and low stoichiometric air/fuel ratio, which leads to increased volumetric efficiency. More complex conversion attempt to exploit methanol’s high octane rating, which reduces the tendency for auto-ignition, through the use of turbo/supercharger and/or raising the compression ratio. For this study it was desired to use these properties to increase the vehicle’s fuel economy potential rather than its power-related performance. Therefore, the conversion was made such that power-performance of the developmental vehicle matched that of the baseline vehicle.

     The properties of methanol mentioned above provide the opportunity to produce the same power-related performance of gasoline engine from a smaller displacement methanol engine. Using this fact, the strategy selected was that of increasing the fuel economy potential through a reduction in the number of cylinders and thus the overall engine displacement. In order to reduce the number of variables changed and thus allows for a direct comparison of the developmental vehicle to the baseline vehicle; it was decided that the same engine, a Chevrolet 2.8L V-6, should be used for both the baseline and the developmental vehicle.

     The developmental engine’s displacement was reduced to 1.9L by modifying two cylinders so that they did not fire, and therefore converting the engine to a V-4 configuration. The two dead pistons were left in the engine for balancing purposes. However, their contribution to the engine’s overall friction was reduced by removing the piston rings and their pumping work was reduced by cutting slots in their piston crown such that the crankcase gases could flow freely around the piston. The developmental engine was then outfitted with a turbocharger in order that engine’s power related performance would match that of the baseline engine. Other than the modifications described above and those required for the conversion from gasoline to methanol fuel, the developmental vehicle’s configuration was same as that of the baseline.

     It was found that an approximate increase of 19% was experienced in the gasoline equivalent fuel economy over the federal test procedure city and highway emission test cycles. It was found that fuel efficiency increased up-to 21% at steady state highway speeds.

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