8.5 Idle Speed and Mixture (% CO) Adjustment
Digifant I idle speed is controlled in basically the same way as Digifant II, using an idle air stabilizer valve controlled by the Digifant control unit. See 7.3 Idle Speed for more information. The only differences on Digifant I are that the control unit has adaptive learning to compensate for operating changes, and the idle (closed-throttle) signal comes from a throttle valve potentiometer.
Digifant I idle mixture is controlled in basically the same way as Digifant II, where the control unit makes adjustments in fuel injector opening time based on feedback from the oxygen sensor. The only difference is that idle mixture control is adaptive. As the engine runs, the control unit learns the midpoint of oxygen sensor range and then uses that value for mixture regulation. The system therefore compensates for all changes in engine operating conditions, including engine wear and altitude.
The Digifant I idle air stabilizer valve is tested in the same way as the Digifant II idle air stabilizer. See 7.3 Idle Speed for test procedures and specifications.
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