STFT only NOT LTFT

[maudyZ28]

Hi all,

sorry if this has been asked before I have done a quick search and will have a mess with my tune this weekend, but just wondering how to run STFT only in OPEN LOOP such that it corrects to stociometric only when commanded fuel stoicometic. Does this exist or will it adjust fueling when commanded is NOT stociometric?

failing this would it sound reasonable to log in CL and check the average WB value over the range where the NB fluctuate to get an accurate reading of the AFR that is run in CL, then adjust the O2 switch points if required, then throw those back in and use LTFT for tuning?

thanks

[joecar]

Hi Maudy,

Set your tune to run OL, then set B4206 to enable; this uses STFT to trim to commanded fuel B3605 cells that are stoich; non-stoich cells will not trim.

Log HO2S11/HO2S21 voltages and see where the average mV is during a long closed loop run, compare this with wideband, and proceed from there... should turn out to be 450 mV.

Then use the Calc.VET tutorial (which uses LTFT (CL) and wideband (PE) to correct MAF and calculate a corrected VE, i.e. two in one go).

[maudyZ28]

thanks joecar, just didn't know if it was as simple as having B4026 set

the switch points at present vary depending on this closed loop mode which relates to load. They are at 450 mV for low modes (low load) and ramp to 550 mV for higher modes (higher loads). Honestly I dont think there will be much difference but I assume this is to trim fractionally richer when under a little more load?

Either way i'll check switch points and the WB. If WB averages about 14.63 then i'll use whatever the NB average at there, or adjust accordingly

[maudyZ28]

well got the VE dialed in well, and the MAF dialed in.

now set car back to dfco and stft enable with stock switch points, but NOT LFTF so still open loop fueling.

Really happy with results, afterwards the O2 switch at about 470 mV which averages at 14.77 ish on WB, so i'm happy with that so i'll go with this tune

thanks to all the guys who have helped me along the way :D