Effects of ethanol content on cast iron cylinder wear in a flex-fuel internal combustion engine-A case study

The localized wear within a four-cylinder automotive spark-ignition internal combustion engine was investigated using a dynamometer durability test. The test engine was equipped with flexible fuel technology, popularly known as “Flex-Fuel”, capable of operating under any mixture of gasoline and ethanol in the fuel. A 2-D profilometer analysis was conducted on engine block specimens from the Top-Dead-Center (TDC) and Bottom-Dead-Center (BDC) positions in order to identify localized wear characteristics. The profiles have shown localized wear dependence in regions of the cylinder bore, as did comparative results between two test conditions: (i) an engine fueled with local gasoline (E25) and (ii) an engine fueled with ethanol (E100). Selected localized wear regions have been characterized using scanning electronic microscopy. Complementary piston ring wear analysis was carried out to assess the remaining coating thickness at the end-of-test. The test with ethanol resulted in the highest localized wear, which occurred at the Bottom-Dead-Center position. A condensed literature review was conducted. An attempt was made to correlate the observed wear features with possible mechanistic theories found in the wear literature. Characterization results indicated that three-body abrasion by carbon residues and piston ring particles is one of the important mechanisms contributing to the cylinder bore wear.