AFR difference between the banks

Mitco39

The car is in open loop under load. You can watch the trims sit at 100% while the car does its thing (which for people trying to follow a 100% means the ECU is not making any adjustments to the correction tables). Then once the load drops down the trim starts again. Uprev however doesn't have the tables mapped for when the ECM switches from open to closed.

It does make sense that there will be a hint of variation per bank. However these trim values everyone are talking about are only active during open loop power enrichment mode. When you are in closed loop the ECU will over ride whatever "trims" you set in when it starts listening to the 02.

For example, lets say you take bank 1 and cut the fuel down by 25%. So on 1,3, and 5 you set the trim to 75%. The fuel relearns are then cleared and the car is set to sit at a constant load under closed loop. At first you will see the trims on bank one sit at 25% as it tries to take your changes into account and yet keep the 02 on that bank happy. Now as you drive you will see the LTFT (long term fuel trim) start to react to the constant high STFT and it will increase to help bring the STFTs back into a better range.

Once the LTFT stabilize you will then see car will run at or around whatever the AFR is set at now completely disregarding your bank trims. Now under WOT this is not the case at all.

I agree that these trims are great under WOT runs, you can clearly see that if one trim bank is constantly higher than the other bank you can then see and adjust these bank trims to compensate for that and ensure that when you do go WOT both banks are running very close to each other in terms of AFR.


If I am wrong I would like to know it. I have been tuning vehicles for 4 to 5 years now and this is the same logic used on the cars I tune. This UPrev setup might be different, but in my 6 or so hours of log time on the weekend this seems to be exactly what is happening in this case as well.

Mitch

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