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On-line individual fuel injector diagnostics from instantaneous engine speed measurements

  • US 6,546,912 B2
  • Filed: 03/02/2001
  • Issued: 04/15/2003
  • Est. Priority Date: 03/02/2001
  • Status: Active Grant
First Claim
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1. A method for cylinder balancing of an engine having a plurality of fuel injectors, comprising the steps of:

  • a. sensing a speed of the engine a plurality of times during a time period;

    b. filtering the sensed engine speed, thereby producing engine speed fluctuation data at predetermined frequencies corresponding to respective ones of the plurality of fuel injectors;

    c. comparing the filtered engine speed fluctuations to a first predetermined threshold value;

    d. comparing the engine speed fluctuations to a second predetermined threshold value when the engine speed fluctuations did not satisfy the threshold conditions in step (c);

    e. if the engine speed fluctuations did not satisfy the threshold conditions in step (d);

    performing steps e.1 through e.4;

    e.1 resetting all fuel injector trims to a predetermined value and calculating the total engine speed fluctuation;

    e.2 for a first one of the plurality of fuel injectors reducing fuel injector fueling by a predetermined value and calculating a new total engine speed fluctuation;

    e.3 generating a fault code for the first fuel injector when the calculated engine speed fluctuations from steps (e.1) and (e.2) are equal;

    e.4 repeating steps (e.1) through (e.3) for each remaining fuel injector;

    f. if the engine speed fluctuations satisfy the threshold conditions in step (d);

    performing steps f.1 through f.3;

    f.1 adjusting the trim for the first fuel injector and calculating the total engine speed fluctuation;

    f.2 readjusting the trim for the first fuel injector until the calculated total engine speed fluctuation is at a local minimum;

    f.3. repeating steps (f.1) through (f.2) for all fuel injectors; and

    g. generating fault codes corresponding to adjustments made to each of the fuel injectors.

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