Patent ID: 8220316

Claim:
A method for determining an alcohol concentration of fuel fed to combustion in a motor vehicle after filling a fuel tank of a fuel system with either a first fuel type of a first predetermined alcohol concentration or a second fuel type of a second predetermined alcohol concentration, the method comprising: prior to having determined whether the filled fuel type is the first fuel type or the second fuel type: establishing a first corridor of possible lambda values associated with filling the tank with the first fuel type, the first corridor being defined between an upper first corridor threshold and a lower first corridor threshold; establishing a second corridor of possible lambda values associated with filling the tank with the second fuel type, the second corridor being defined between an upper second corridor threshold and a lower second corridor threshold; and dynamically adapting at least one of the upper threshold and the lower threshold of each corridor as a function of time and fuel consumption such that an initially large width of at least one of the corridors becomes increasingly smaller; determining whether the filled fuel type is the first fuel type or the second fuel type, based on the dynamically adapted first and second corridors, changes to a lambda value measured by a sensor, an alcohol concentration of the fuel tank before filling, and volumes of the fuel tank before and after filling; and in response to determining whether the filled fuel type is the first fuel type or the second fuel type, considering only the corridor corresponding to the determined filled fuel, and ignoring the other corridor, for a subsequent evaluation of measured lambda values.