Technical Paper
Analysis of Oil Sump Contamination with Ethanol in Flex Fuel Engines after Crank and Warm-up
2009-10-06
2009-36-0117
A flex fuel engine which operates with high ethanol content fuel can show a significant level of oil sump contamination with ethanol depending on startup coolant temperature and driving behavior. In general, the lower the coolant and the more aggressive the driving pattern the higher the oil sump contamination. As the engine warms up and the oil temperature increases, the liquid ethanol mixed in oil sump evaporates (boil-off phenomenon) and returns into the induction system through the engine venting system. Oil contamination and boil-off phenomena have to be properly considered by the engine management controller so that closed loop fuel control, fuel trim diagnosis and ethanol learning are not fooled by the extra fuel coming by blow-by. This paper presents the results of an analysis conducted in a GMPT 1.4L Flex Fuel engine running with E85 and E100 fuels.