Dyno Tuning
EFI computers have several modes of operation. These modes are determined by the output power needed from the engine's operating conditions:
Race Engine Building and Maintenance
The ECU measures teh air/fuel ratio (A/F) from the O2 (or lambda) sensor. THe ECU works to maintain a constance A/F ratio (14.7:1). This ratio is optimal for the catalytic converter to reduce exhaust emisions correctioly. Also, an 14.7 A/F ratio is the ideal sweet spot for the lambda sensor to work accurately, and this gives a good feedback signal.
EFI Computer Programming
This differs from closed loop mode as the lambda sensor signal is ignored. The ECU controls the fuel injectors wihtout feedback that the calculated fuel delivery rate matches what the engine receives. Without feedback, the loop is open, there by giving the term "open loop."
Race Car Preparation
This only occurs at Widoe Open Throttle (WOT) and is only determined by the Throttle Position Sensor (TPS) from about 60% wot onwards. The ECU in this mode, ignores the lambda sensor and forces a richer A/F ratio than 14.7:1. This is becuase engines develop more power with a slightly richer mix. This is the area that
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