E40 correlation between small pulse adders and LTFTs?
I'm trying to understand why commanded AFR is 14.7, wideband is reporting 13.8 while LTFTs are +15%. The INJPW is at the minimum 1.3ms setting. Are the B1204 small pulse adders or B1210 Injector correction tables adding to the fuel trims?
My changes have been to the B1203 Min pulse and B1210 correction tables. Trying to address a high spike in my VE tables at cruise.
2005 E40 LS2 GTO running the boost OS.
Post log file and tune file.
This was intended as a theoretical question. The last 300 frames of this log are what I'm referring to. Idle before shutdown.
Last edited by ACCLR8N; May 30th, 2013 at 01:23 PM.
The SPA and injector correction tables are adjusting the fuelmass sprayed by the injectors (i.e. trying to "exactly" model the injectors)...
so, technically, they are not adding to the fuel trim, by they may be adding fuel which may effect the trim.
Commanded: 14.7
Wideband: 13.8
LTFT: +15% (as is pegged above 15%...?)
Assuming the injector tables are all correct (matching the injectors) then that says that the PCM is trying to achieve trim by adding +15%, but wideband shows 13.8 which is richer than commanded stoich...
- are you sure the wideband is reading correctly...?
- are you sure the NBO2's are working correctly...?
- what is the stoich AFR of the fuel you're using...?
Which wideband do you have (some assume a slightly different stoich than the PCM)...?
Now if the injector tables were not correct for those injectors, then SPA would alter the trims only when the injector on time is very small (when injector on time it is large, the SPA is relatively small).
No, it is not pegged at 15%. The average at idle for bank2 is just over 15%, bank1 always runs slightly higher. I'm pretty sure the injector tables are incorrect. The LTFT confused me in trying to correct it. I am as certain as I can be all the O2's are performing correctly. Everything makes sense at higher pulsewidths. My LC-1 wideband typically reads about 0.2 richer than the PCM. I'm assuming 14.7 stoic for my 93 pump gas (straight dinasaur).
I was hoping for some insight on why the LTFTs are adding so much when the WO2 is reading rich. The rich part makes sense as the injectors are at minimum set PW. Why add fuel though? Is it the mechanism to keep the injectors at or above 1.3ms?
The trims are just trying to trim to stoich... you say the LTFT's have stabilized at 15%, but the wideband is reading 13.8...
try this: disable LTFT and enable STFT and see what the wideband says while STFT trimming (hint: should look like it's tightly oscillating around stoich).
Also log HO2S11 and HO2S21.
After playing with the settings back and forth, the LTFT and injector min pulse are clearly tied together. My guess is the LTFTs are ramped up to sustain the injector open long enough to meet the minimum pulsewidth.
Moving on...
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