Nistune Forums

Hi all

During tune of N15 Almera gt with seriously modified SR20DE I noticed some problems with fuel delivery adjustment. From some reason, AFR does not respond diretly to fuel map values itself. If you check standard map, most of it is at 0, also it has enabled O2 feedback in whole map.
Only way was to use K konstant for overall map and inj. latency for idle. It works quite good, but in part of light load it need adjust AFR a bit. Then I found that VE table can affect AFR quite a lot, specially at high loads, most of tune here I made by VE table. Anyway, it looks that it doesnt affect part thorttle load/cruising or idle at all.... For sure, using O2 feedback should solve situation, problems was that standard lambda probe was fault (jumping from 0V to 0.8V rapidly and repeating) so I cannot use it. Anyone can help me with this issue or I really have to use O2 feedback for part load as only AFR regulation?
Thank you for your help

Factory O2 sensor is SUPPOSED to jump rapidly between 0-0.8v ,that shows the ECU is trimming the mixture between rich (over 0.6v) and lean (below 0.4v). The factory sensor is narrowband, not wide band so it will not give direct AFR numbers, only indicate rich or lean.

Turn off O2 feedback flags firstly (Feedback flag parameter) during tuning

Once you are satisfied with AFRs coming out exhaust then turn it back on afterwards

VE table in these ECUs are used for adjustments whilst O2 feedback enabled

cozzmo: I dont mean real rapid voltage change that indicate stoichio status, but fluctuation in about 1second interval what casued visible AFR change on wideband synchronised with voltage fluctuation, you can even feel it as engine torque changes or at idle as visible rpm fluctuation...

matt: all what I wrote in first post was done with O2 feedback flag turned off, as I cannot use it becouse of standard probe voltage fluctuation. In this situation I have those problems with fuel trimming...so my question is still here....
theoretically, if I replace narrow band probe, it should solve all problems at low loads...But then there is question what are conditions for narow band probe use, as it is enabled in whole map as standard?

Are you noticing your injection pulsewidth change when you adjust a bunch of cells around the maptrace cursor? What is the ECU part number here that you are using?

Narrow band use is determined by the coolant temp and amount of rpm/load. We havent identified exact parameters for this switch over however

I have to check inj. pulse time, as I use just wideband as feedback. ECU part. number is 1N4XX, N15 Almera SR20DE.

Let me know how you go. If still issues I'll run it up on the bench next week when I find some time

Hi Matt, bench test will be very useful anyway, Im still didnt test it, but have to do in short time again. As I know that fuel map adjustment just dont affect AFR, I will appreciate if you can test this at the bench in meantime...