A Comparative Analysis of Ethanol Versus Gasoline as a Fuel in Production Four-Stroke Cycle Automotive Engines 952749

This paper presents the findings of a study that compared the fuel efficiency, power, emissions, engine wear and material compatability characteristics of automotive four-stroke cycle engines fueled by E95 (95 % ethyl alcohol and 5% lead free regular gasoline) and 87 pump octane number lead-free gasoline.

A group of six senior Automotive Engineering Technology students, conducted the research over a one-year period. Two Mankato State University faculty served as directors for the project. The laboratory facilities at Mankato State University were used for vehicle modification and testing.

Two identically equipped 1994 Geo Metros with 1.0 liter, three cylinder, throttle body fuel injected engines were used for this study. After a 6440 km (4000 mile) break-in period, to assure the cars performance characteristics were equal, one of the vehicles was converted to run on E95. The conversion included a programmable engine management system to control the fuel and ignition systems; the increasing of the compression ratio; the addition of port sequential fuel injection.

Fuel economy was compared in 16,100 kilometers (10,000 miles) of matched testing. Power comparisons, emission levels and oil quality were measured before, during and after 16,100 matched kilometers (10,000 miles) of almost exclusively highway driving on a 383.5 km (238.3 miles) route. Both vehicles were then disassembled to evaluate engine wear and inspect for corrosion and deposits.

The E95 vehicle had a 15.2% gain in equivalent fuel economy and developed 14.5% more power at the drive wheels. At this time a FTP emissions test has not been performed, however, both vehicles emission levels would pass the State of Minnesota Test. There was no evidence of differences in engine wear, oil or material compatibility between the two vehicles. There were fewer deposits on the piston top and intake valves on the ethanol engine. The cost of operation was calculated to be 90.9% greater for E-95.