Hondata

I have noticed in most FN2's I have tuned that after a while (in some cars this happens immediately, in other's after a while) that short term correction goes to 47% and stays there although actual AFR is below 11:1. At first I thought this was due to faulty stock O2 sensors (Honda had a recall on this) but it is not. Today I tuned a car and used the EGR lift input for an external wideband and the same things happen. Actual AF stays below 11, short term correction goes to +47%, and AF display on the ECU is around 13.5! (this is why the stock ECU keeps adding fuel). External wideband was carefully grounded on G101. Please find attached datalog from a dyno pull and the calibration.

I finally used a MAP calibration to remedy this problem (open loop above 700mbar) and narrowed down the short term correction range but this cannot be done on MAF calibration. And most customers DO need the fuel level gauge etc. So we have to find a solution (one solution to the problem would be the ability to narrow down the short term correction margin on AFM calibrations as well).

WOT fuel correction tables cannot be higher than 0.85 / 12.50:1 otherwise this will happen.

Thank you so much. It completely crossed my attention! So, only MAP calibrations can run leaner AFRs, right?

Both AFM and MAP calibrations will do odd things if the WOT correction tables are too lean, but it seems worse on the AFM calibrations.

CivicVTi wrote:Thank you so much. It completely crossed my attention! So, only MAP calibrations can run leaner AFRs, right?

If you want to run leaner with a AFM calibration then adjust the AFM Flow tables.

CivicVTi wrote:I have noticed in most FN2's I have tuned that after a while (in some cars this happens immediately, in other's after a while) that short term correction goes to 47% and stays there although actual AFR is below 11:1. At first I thought this was due to faulty stock O2 sensors (Honda had a recall on this) but it is not. Today I tuned a car and used the EGR lift input for an external wideband and the same things happen. Actual AF stays below 11, short term correction goes to +47%, and AF display on the ECU is around 13.5! (this is why the stock ECU keeps adding fuel). External wideband was carefully grounded on G101. Please find attached datalog from a dyno pull and the calibration.

I finally used a MAP calibration to remedy this problem (open loop above 700mbar) and narrowed down the short term correction range but this cannot be done on AFM calibration. And most customers DO need the fuel level gauge etc. So we have to find a solution (one solution to the problem would be the ability to narrow down the short term correction margin on AFM calibrations as well).

it happens a lot with the earlier versions of the software... however i tried with the later versions, it does seem to remedy the situation.

however, the erratic fuel gauge and MAP tuning is a hassle.

i did not hear anything about the O2 sensor recall by Honda in my area, but they do tend to go out very easily, thus causing all the S. term corrections, etc, at least in some of my cases.

civicRSA wrote:

CivicVTi wrote:Thank you so much. It completely crossed my attention! So, only MAP calibrations can run leaner AFRs, right?

If you want to run leaner with a AFM calibration then adjust the AFM Flow tables.

yes thats right , i am at 13.2-13.3 true afr , while target tables are at 12.2-12.4 , couldnt find another way past the 12.5 limitation ,than to trick the maf through those tables , and there is no way my car would be at 12.5 afr 8)

no problem with the short term fuel trim in 4 fn2s including mine