Long term / closed loop fuel trim on K series

[Razathorn]

It is best to disable closed loop operation while tuning. Otherwise what commonly occurs is that the ECU will alter the mixture using the long term adjustment while the car is idling between dyno runs, which means that the mixture is not repeatable between dyno runs.

If changes are made to the engine which alter the amount of fuel that is delivered (bigger injectors, increased fuel pressure or altering the air temperature sensor voltage) the ECU will compensate the best it can using the long term adjustment. Under high load when the ECU stops running in closed loop the long term adjustment is still used so increasing fuel delivery via these means in not recommended unless the ECU is recalibrated or closed loop disabled.

Does the long term fuel trim affect open loop opreation? Is this information accurate for K series?

I have always tuned WOT or BOOST fuel with closed loop enabled. I've never really had any issues or wandering a/f ratios. I'd obviously would turn off closed loop for part throttle tuning, but I wasn't aware that long term fuel trim could affect open loop WOT or BOOST operation.

Wayne

[Hondata]

The long term fuel trim does not affect open loop with the K-Series, but use open loop when tuning.

[640k]

The long term fuel trim does not affect open loop with the K-Series, but use open loop when tuning.

I've been struggling to understand the benefits of running open loop during tuning (especially on the street). So far all of my tuning has been WOT. Could I be depriving myself of an accurate tune otherwise?