Hondata

Something doesn't make sense. Today I made two WOT datalogs with the same exact cal. They very done 20 minutes apart and the IAT was only 3 degrees F different. The only difference is that after the first pull I re-uploaded the cal to the ECU.

Datalog #1 was done first and the A/F is leaner throughout most of the RPM band (~ 13.0:1 on average)
Datalog #2 with the same exact kal is now a little richer throughout most of the RPM band. (~12.8:1 on average)

My desired AF that I have preset into k-manager is 13.2:1

The part that doesn't make sense to me is that when I click "display fuel adjustment values", the leaner datalog #1 (closer to my desired lambda value) is telling me to take out more fuel than the richer datalog #2......

Does this have something to do with the Long term fuel trim? On the first datalog there is a -3% L.Trim showing on the graph. On datalog #2 there is 0% L.Trim showing on the graph. I assume it's zero because I just re-uploaded the kal and it hasn't had time to learn it yet.

I was under the impression that fuel trim does not play a role in Open Loop operations.

I have the two datalogs as well as my kal uploaded for you to look for yourselves.

I calculate the difference at just over 0.1 AF point. The richer datalog is indicating that more fuel needs to be removed, and the leaner less. 0.1 AF point is not much - to get better accuracy than that you need to perform 3 dyno runs / datalog in a row, with the same starting temperatures and time interval, and take the data from the last run. The difference in both IAT and ECT between runs could easily result in a 0.1 difference.

If you are tuning then it is best to set the minimum and maximum short term trims to 0.