on my logger, i have low, med, and hi fuel trims, and also o2 trim. if all you have is short term and long term, long term will change slowly. here is how i set my LO fuel on my afc. on the logger, select o2 trim, o2 volts, rpm, low, med, and hi fuel trim. then, with the motor FULLY WARMED UP, set the afc at 1k, hold your rpm to 1k, and look at your o2 trim. it should be bouncing all around, but what it is trying to do is keep it at 100. low fuel trim also wants to be at 100. if low fuel trim is below 100, you are rich, and your o2 trim will be bouncing around above 100. adjust your afc until your o2 trim averages 100, you should see your low fuel trim slowly changing. it will also become 100. adjust each level of the afc, 2k, 3k, 4k. on my car, above 4k, the ecu goes open loop, and uses set fuel maps, so it pretty much has no effect on the LO throttle settings. on the HI trottle settings, you will need to go out and do some wot pulls and datalog them.
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