To reduce atmospheric CO2 emissions as well as crude oil consumption, several countries have started to increase the ethanol content in gasoline. Brazil is unique in this respect, where pure ethanol fuel (E100) is offered on the market, however the use of pure ethanol as a fuel, significantly affects engine oil dilution.
High oil dilution directly affects the injection system, during the fuel evaporation process. The evaporation behaviour is mainly characterized by the chemical composition of the fuel accumulated in the oil, as well as the engine warm-up behaviour.
A high proportion of the accumulated hydrocarbons in the engine oil evaporates, as engine oil temperature increases. There can be dramatic effects on systems that are not designed to consider the evaporated hydrocarbons. Effects such as misfire or engine stall are well known phenomena of unconsidered fuel evaporation.
The Continental oil dilution model is able to determine the oil contamination during every engine operating point. It is possible to differentiate between several typical fuel types for the accumulation determination and based on that, to model an evaporation mass fuel flow from the crank-case into the intake manifold. Using the model, the impact on the overall system can be considered correctly and the engine combustion stabilized.
This paper highlights the fuel accumulation and evaporation model for flex-fuel engines based on a multiple component approach. The general principle of the algorithm will be explained and the system reactions of the function are pointed out and compared to previous systems.