I did disable the LTFT relearn but not the STFT during my AutoVE tuning. Just to be sure I had enabled the LTFT I downloaded the tune from my car and checked the LTFT setting and it was enabled. I've gone back over every parameter that was changed and then put back to where it was originally and can't find anything wrong. My head's about to burst.
When AutoVE tuning, you should have all closed loop operation disabled. Meaning, no STFTs.Originally Posted by VetPet
I did disable the LTFT relearn but not the STFT during my AutoVE tuning. Just to be sure I had enabled the LTFT I downloaded the tune from my car and checked the LTFT setting and it was enabled. I've gone back over every parameter that was changed and then put back to where it was originally and can't find anything wrong. My head's about to burst.
According to the AutoVE tuning document, you only need to disable the LTFT's. With LTFT's disabled, changes in STFT's that would normally update the LTFT's don't have any effect so there shouldn't be any need to disable the STFT's as well. This is my understanding of the theory and I could be wrong. In any case, I've enabled the LTFT's and don't see and data when I'm logging in either the data tab or the LTFT maps. My monitored WB02 AFR is very close to what's being commanded so I could assume that the LTFT's are pretty good but I'd like to get the actual data. Something here doesn't make sense.
I just want to add one thing. My battery was drained because I left my DC to AC converter turned on and plugged into the power supply in the car. This would be the same as disconnecting the battery which means that the LTFT's the PCM had learned would be wiped out and it would have to relearn them again. I did one more data logging session after I got the car started before I put the PCM into closed loop, speed density. Is it possible that the reason I didn't see any data is because the car needs to be driven again for a while before I'll see any LTFT data? Just a thought but I thought I'd throw it out there.
Thanks,
Setting B4205 to maximum should disable your closed loop.
The fuel trims learn very quickly. For example, if your LTFT for a particular cell was say 10%. That 10% would appear back in the LTFT cell after about 1 or 2 minutes of driving in that cell under the correct conditions.I just want to add one thing. My battery was drained because I left my DC to AC converter turned on and plugged into the power supply in the car. This would be the same as disconnecting the battery which means that the LTFT's the PCM had learned would be wiped out and it would have to relearn them again. I did one more data logging session after I got the car started before I put the PCM into closed loop, speed density. Is it possible that the reason I didn't see any data is because the car needs to be driven again for a while before I'll see any LTFT data? Just a thought but I thought I'd throw it out there.
Thanks,
What most people mean when they say something like "the LTFTs take 100 miles or more to learn" is that it takes 100 miles or more to hit every cell for at least long enough for the PCM to learn the correct trim.
Just rambling here...
Basically the learning process goes like this:
PCM sees O2 sensor voltage is too far fromthe crossover point (defined by {B4105}) for too long (defined by {B4113}).
So it adjusts the STFT by {B4111} or {B4112} to bring the O2 sensor voltage back towards the crossover point {B4105}.
After the STFT correction has reached its limit {B4115} and {B4116} the LTFT is updated and the STFT is reset back to 0. You can observe this happening if you clear the LTFT and then log STFT and LTFT. (Only if your VE table is far enough out to require significant trim changes).
The LTFT cells are updated from the LTFT value using the filter in {B4106}.
The process is very efficient at getting the fuel delivery accurate and remembering it and continually adjusting it over time as conditions change and components deteriorate.
Regards
Paul
Before asking for help, please read this.
^^^^ wow. never seen it spelled out like that before. Almost makes me want to try CL again.
Appreciate the detailed information regarding STFT/LTFT's. The issue is still why I can't get any LTFT data after enabling LTFT learning again. The MAF is disabled as outlined in the AutoVE tutorial and I added the LTFT Pids. As I watch the data tab LTFT Pids and the LTFT Maps the data is always at zero. No LTFT data is showing up at all and I've driven for quite a while. Are my values possibly in an out of bounds range that don't show up and is this even possible? "I think I'm not in Kansas anymore Toto"
This is going to drive me to
Log the PID {SAE.FUELSYS} which will tell you whether the PCM is in closed loop or open loop. If it is in open loop the LTFT will not be updated (i.e. no learning).
Also try logging {GM.SSTATE05} it also contains some intersting bit fields to do with fuel status:
Code:Description Status=0 Status=1 Decel Fuel Cutoff Inactive Active This start Warm Cold Fuel Trim Learn Disabled Enabled Heated O2S Bank 2 Sensor 2 Not Ready Ready Heated O2S Bank 2 Sensor 1 Not Ready Ready Heated O2S Bank 1 Sensor 2 Not Ready Ready Heated O2S Bank 1 Sensor 1 Not Ready Ready Fuel Loop Status Open Closed
Before asking for help, please read this.
Blacky, Added the pids suggested and monitored data. SAE.FuelSys shows it to be in closed loop. GMState05 pid also shows fuel loop system = closed, fuel trim learn = enabled, decel fuel cutoff = inactive. I reloaded my original tune prior to doing any VE tuning and was able to get average LTFT and just LTFT's. Also logged the 02 sensor voltage to see if they were working which they were. Loaded the AutoVE tune back up and tried to log LTFT's again but no values once again. Also getting no values for STFT's. I checked to make sure I had enabled both the LTFT & STFT's again and they were. I can't make heads nor tails out of this. Sounds like something from the X files.
pardon my french.
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