S&S Cycle EZFI on 2008-09 Touring Models - Manual (Page 8)

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Because every industry has a leader
Tuning on Closed Loop Vehicles.
Tuning for performance modifications on motorcycles that run closed loop fuel control require a higher level of difficulty. The reason for this is
because those ECMs use feedback from oxygen sensors to continuously re-calculate the amount of fuel needed at each operating point. In general,
most stock ECMs target a near-stoichiometric (14.6) air fuel ratio (AFR) for the operating range of 0 to 4500 RPM and 0 to 80% throttle. If you use
EZFI™ to alter the fuel amount in this range, the stock ECM will undo your change to force the AFR to its 14.6 target.
For example, if you are in the low cruise range of 1500 RPM and 15% throttle, the ECM will target a 14.6 AFR. If you tune +10% fuel to target a richer
AFR, the ECM will detect this extra fuel and reduce it’s base fuel amount to return the AFR back to 14.6.
There are two options for tuning closed loop motorcycles. Both achieve the same result. The first is to do nothing. Don’t tune within the stock closed-
loop range defined above. This roughly corresponds to EZFI modes 1, 2, and 3. Leave the adjustment in these three modes at 0. Let the ECM run
closed-loop to target its programmed AFR. Tune the remaining modes, 4 – 9, for wide open throttle conditions.
Your second tuning option is to use EZFI to help the ECM return to its target AFR. The main reason to do this is if the stock ECM is running out of
fuel adjustment and setting the Check Engine light. This would only be necessary on the most extreme engine modifications, where fuel delivery
requirements are drastically different from the stock engine.