Abstract: A method is provided for monitoring the integrity of a fuel composition sensor in a flexible fueled vehicle. At ignition-on, the fuel composition sensor is tested for electrical and rationality viability. After ignition-on, the fuel composition is periodically, non-intrusively, tested for potential rationality errors. Should the non-intrusive testing indicate that a potential error exists, the fuel composition sensor is intrusively tested for rationality errors. If the intrusive test detects that the fuel composition sensor is malfunctioning, the engine control system converts to a limp-in mode and sets the engine operating parameters based on feedback from an exhaust gas oxygen sensor system.

Abstract: The present invention provides a flexible fuel compensation system for determining the percent alcohol content of fuel in a flexible fueled vehicle at the instance of fueling and in an open loop operating mode. According to the invention, two estimated percent alcohol content values are calculated based on the old fuel mixture's alcohol content and two fueling possibilities. A first value is calculated for the possibility that E85 fuel was added to the tank and a second value is calculated for the possibility that E0 fuel was added to the tank. If the inferred ethanol content increases above a positive threshold during closed loop operation, the system assumes that E85 fuel has been added to the tank. Conversely, if the inferred ethanol content decreases below a negative threshold, the system assumes that E0 fuel was added to the tank.

Abstract: A method is provided for triggering a system for learning the percent alcohol content of a fuel used in a motor vehicle capable of operating on more than one type of fuel. The fuel composition learning system is triggered each time fuel is added to the vehicle's fuel tank, each time the engine is started when the fuel volume in the fuel tank falls below a given value or if a fuel level sending unit malfunction has been detected. The fuel composition learning system is also triggered if an error is detected in the value of the learned percent alcohol content of the fuel.

Abstract: The present invention provides a method of compensating for a boil-off condition in a flexible fuel compensation control system for a flexible fueled vehicle with a PCV solenoid. The methodology determines both the presence and extent of boil-off corruption and handles closed loop controls normally as if no boil-off corruption exists. The methodology also determines the amount of boil-off corruption being introduced through the PCV system and updates the flexible fueled vehicle fueling during a blend change between ethanol and gasoline. Additionally, the methodology determines when boil-off corruption is no longer influencing closed loop fuel control.

Abstract: The present invention provides a method for controlling combustion parameters of an internal combustion engine during wide open throttle or part throttle enrichment operation. Oxygen sensor rich and lean counts above and below a stoichiometric air/fuel ratio are counted during an injector pulse width period while a fuel concentration determination is being made at wide open throttle and part throttle enrichment. The ratio of lean counts to rich counts is compared to a calibratable value for incrementing the fuel concentration delivered to the internal combustion engine. The fuel concentration is further controlled if a boil-off condition is detected.

Abstract: The present invention provides a flexible fuel compensation system for determining the percent alcohol content of fuel in a flexible fueled vehicle at the instance of fueling and in an open loop operating mode. According to the invention, two estimated percent alcohol content values are calculated based on the old fuel mixture's alcohol content and two fueling possibilities. A first value is calculated for the possibility that E85 fuel was added to the tank and a second value is calculated for the possibility that E0 fuel was added to the tank. If the inferred ethanol content increases above a positive threshold during closed loop operation, the system assumes that E85 fuel has been added to the tank. Conversely, if the inferred ethanol content decreases below a negative threshold, the system assumes that E0 fuel was added to the tank.

Abstract: The present invention provides a flexible fuel compensation system for controlling operating parameters of an internal combustion engine based on a learned value of the percent alcohol content of the fuel using an oxygen feedback system. The methodology determines a fuel composition multiplier based on the percent alcohol content and implements gasoline operating parameters for the internal combustion engine if the fuel composition multiplier is less than a first threshold value, mixed gasoline/alcohol operating parameters if the fuel composition multiplier is greater than the first threshold value, and high concentration alcohol operating parameters if the fuel composition multiplier is greater than a second threshold value for a number of comparison checks. After a predetermined period, the fuel composition multiplier is updated and re-compared to the first and second thresholds and the appropriate one of the aforementioned operating parameters is implemented.

Abstract: The present invention provides a method for controlling the combustion parameters of an internal combustion engine with an oxygen sensor prior to a closed loop operating condition. If the output voltage of the oxygen sensor indicates a lean air to fuel ratio condition, the percent alcohol content is incremented to a limit based on an E85 possibility curve. If the voltage output of the oxygen sensor indicates a rich air to fuel ratio condition, the percent alcohol content is decremented to a limit based on an E0 possibility curve. After the end of the fuel blending period or when the internal combustion engine reaches a closed loop mode, control of the combustion parameters of the internal combustion engine are returned to normal regime oxygen sensor feedback control.