i was told that on these cars the fuel trims will always zero out on wot and will not affect the tune at all if the fuel trims were reading positive, i know on most cars if you have positive fuel trims it will add that positive percentage to the wot and make the car run richer, does anyone know for sure about this, thank you

 

The fuel trims are just used for closed loop fueling. They are not applied during open loop fueling.

The biggest impact a very positive or very negative LTFT will have is during the transition from closed loop to open loop, which may cause a lean or rich spike in that transition area.


Eric

 

thank you, i just want to make sure, i know on other cars if you have positive fuel trims while cruising it will add that amount back into your wot

 

Does everyone still agree that fuel trims do not affect open loop fueling?

 

Yes, the fuel trims DO NOT effect the open loop AFRs. The trims are a result of o2 feedback during idle and part throttle cruise, when the threshold is met where it goes to open loop, then it is directly corelated (sp?) to what the open loop map has for a given load/rpm or whatever the map is scaled in. It is based on the multiple sensors in the system to get to that but the o2 sensor is not one of the sensors used.

Josh