Compression ratio effects on an ethanol/gasoline fuelled engine performance

This work investigates the influence of compression ratio on the performance of a spark ignition engine fuelled by a blend of 78% gasoline-22% ethanol (E22) or hydrous ethanol (E100). A 1.0-L, eight-valve, four-cylinder, production engine was tested in a dynamometer bench varying the speed in the range from 1500 to 6500 rev/min. Three compression ratios were investigated: 10:1, 11:1 and 12:1. The performance parameters evaluated were torque, brake mean effective pressure (BMEP), power, specific fuel consumption (SFC), thermal efficiency, exhaust gas temperature and volumetric efficiency. The results showed that higher compression ratios improved engine performance for both fuels throughout all the speed range investigated, with major effects being observed when hydrous ethanol was used.