Mechanical Engineering students at Texas Tech participated in the 1989 SAE Methanol Marathon in which a 1988 Chevrolet Corsica was converted to run on M85, a blend of 85% methanol and 15%hydrocarbon fuel. This report describes modifications to the Corsica accomplished in preparation for the continuation of this program, the 1990 SAE Methanol Challenge. The modified Corsica place second overall.
In response to the 1990 program requirements, the Corsica was modified to enhance engine, transmission, and suspension performance. Engine modifications include improving cylinder head flow efficiency, changing cam profiles, modifying the engine bore and stroke, using lighter weight pistons with modified rings, using roller-tip rocker arms, enlarging the exhaust runner ports, and installing a specially developed catalytic converter system. The transmission was modified with a lower ratio fifth gear and the suspension was strengthened. The heated combustion air inlet was retained from last year's vehicle and an ether injection cold-start system was added. The engine was tuned with the computer system provided by General Motors.
Development of a medium priced vehicle with good performance, fuel economy, and reliability was the design philosophy adopted. Performance augmentation components such as turbochargers were not included. All modifications were selected for ease of implementation during manufacturing with little or noincrease invehicle cost. The modifications made produced a balanced vehicle with a substantial increase in power and fuel economy. The Corsica runs smoothly and is well behaved in traffic.
Methanol has received considerable attention in the past few years as an alternative to petroleum-based fuels for motor vehicles. Methanol is an alcohol that can be used neat (100%), in near-neat form, or in low concentration blends with gasoline. Although there are problems to be resolved concerning the use of Methanol, it burns cleanly and reduces combustion chamber deposits. Methanol also has a favorable impact on emissions-the exhaust residues from a methanol fueled vehicle are lower in photo-chemical reactivity (diminishes the ozone problem) than those from a typical gasoline fueled vehicle. Methanol will also provide a significant increase in engine efficiency over that of gasoline fueled engines. Estimates of this increase vary from 10% to 30% in most references. However, these estimates are based on modifications to existing engines to convert them from gasoline to methanol. Engines burning methanol typically produce 20% to 40% more power than their gasoline counterparts. Thus, a significant increase in energy efficiency can be realized by replacing gasoline engines with substantially smaller methanol engines with no loss in vehicle performance. The smaller engines burn less fuel directly and they also reduce vehicle weight, thereby providing additional fuel savings. The Corsica modifications made by the Texas Tech team for the 1990 SAE Methanol Challenge should result in a fuel consumption rate of approximately 24 mpg compared to the 29 mpg rating for the car on gasoline. On a mile per BTU basis this corresponds to approximately a 40% improvement for a vehicle that has significantly more throttle response and overall performance.
The objective of the Texas Tech team was to modify the Corsica to burn M85 fuel efficiently without exotic or expensive hardware changes. Modifications to the Texas Tech car (excluding the fuel system components supplied by GM) could all be incorporated into production vehicles easily in a short period of time with little or no increase in manufacturing cost. The vehicle modifications made by the Tech team are described in the following sections of this paper.