The first step in determining how much fuel to deliver to the engine is calculation of basic injection duration. Basic injection duration is a function of:
• Long fuel trim (LFT) correction factor
This basic injection duration value is the ECM's best guess at the actual injection time necessary to achieve an ideal air/fuel ratio. Generally, this basic injection calculation is very accurate, typically within ± 20% of what actual injection needs to be. Once within this range, the ECM can trim the air/fuel ratio to stoichiometry based on oxygen sensor information.
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