Importance

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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. Accordingly, if the vehicle is shut down before a more accurate ethanol content determination is complete, the inferred ethanol content follows either the first or second estimated alcohol content value until the system reaches a closed loop operating condition.

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First Claim