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Air/fuel control system for an internal combustion engine

  • US 5,598,703 A
  • Filed: 11/17/1995
  • Issued: 02/04/1997
  • Est. Priority Date: 11/17/1995
  • Status: Expired due to Fees
First Claim
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1. An air/fuel control method for an engine responsive to first and second exhaust gas oxygen sensors positioned in the engine exhaust respectively upstream and downstream of a catalytic converter, comprising the steps of:

  • modulating an engine fuel flow signal;

    correcting said fuel flow signal by a feedback variable derived from the first sensor to cause engine air/fuel operation near a desired air/fuel ratio;

    offsetting said fuel flow signal by a first value during a first predetermined time to cause a corresponding rich offset in engine air/fuel operation and offsetting said fuel flow signal during a second predetermined time by a second value to cause a corresponding lean offset in engine air/fuel operation; and

    biasing said fuel flow signal with a rich fuel bias when the second sensor indicates excessively lean engine exhaust in response to said lean fuel offset and biasing said fuel flow signal with a lean fuel bias when the second sensor indicates excessively rich exhaust gases in response to said rich fuel offset.

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