Importance

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Abstract

An apparatus for use with an internal combustion engine operable on either of gasoline fuel and gasoline/alcohol fuel blend. The apparatus comprises an alcohol concentration sensor for sensing the alcohol concentration of the fuel to be delivered to the engine, an oxygen sensor sensitive to the oxygen content of exhaust gases discharged from the engine for producing an air/fuel ratio feedback signal, and a control unit coupled to the alcohol concentration sensor and the oxygen sensor for controlling the amount of fuel metered to the engine. The control unit calculates a basic value for the amount of fuel metered to the engine based on engine operating conditions and corrects the calculated basic value for the sensed alcohol concentration. A correction factor, which is set within a control range defined by predetermined upper and lower limits, is calculated based on a deviation of the air/fuel ratio from a stoichiometric value. The calculated basic value is corrected based on the calculated correction factor to provide a closed loop air/fuel ratio control. The upper and lower limits are changed to expand the control range in the presence of an alcohol concentration signal change exceeding a predetermined degree.

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First Claim