Magic Chicken

iTrader: (1)

I second that!

Another_User

STFTs are not faster changing LTFTs. There are many other conditions that will cause your STFTs to go up and down. Tuning by LTFTs makes more sense to me anyways. I would imagine STFTs can even be pulled "lean" by downshifting and exiting PE mode, which would not show up in the LTFTs.

Magic Chicken

iTrader: (1)

From what I understand, STFTs might as well be called Real Time Fuel Trims, and LTFTs might as well be called Average Fuel Trims. You're right, those conditions wouldn't show up in LTFTs, but it would be considered in averaging the fuel trims.

WS6snake-eater

FWIW I'm sticking to using the LTFT's at least until I get a WB.

ram-it

Thanks for explaining the STrims for me.

horist

I'm using STFT at the advice of a friend that's much more knowledgable than I on this subject... and it's definetly been going well...

from my understanding... short term trims are instantaneous... wha'ts the car doing now... whereas when you introduce long term trims , it affects the overall fueling since they are an average or STRIMS.... the nice thing about using STRIMS only is that you don't have the PCM using hte LTRIMS to vary the fuel delivery..... if you use LTRIMS it doesn't update as quickly... whereas STRIMS are a true average (not an average based on the use of an average calculation performed by the PCM) ...

here's tonights log (before I made a tune change)


tuning for +/- 4 ... and those green sells (big green) I was definetly feeling... cruise was set at 40mph in 3rd gear and car seemed to drop RPMs then pick up... i looked at my laptop and saw I was in those sells running really rich ...

Another_User

Sweet. You are hitting a very similar brick wall to what I did. If you figure it out I am anxious to hear. My trims to the left and top were lean, everything in the middle ok.

WS6snake-eater

Man you guys got me so damn confused now...I thought my stuff was looking good, now I'm stuck between the conventional method using the LTFT's and the new STFT method. I thought that the two would go hand in hand, but comparing my two histograms, of STFT's and LTFT's I'm seeing that the STFT's are reporting lower than my LTFT's...

Magic Chicken

iTrader: (1)

Wow, that doesn't look too good. I'd get the LTFT's to where they should be and then fine tune with the STFT's afterwards.

WS6snake-eater

The funny thing is I've been doing a lot of tuning using the LTFT histogram and, I had the table looking great...all -2 to 0, Then I converted the data to a CSV file and started doing some more looking and realized that my left o2 was not reading correctly...So I got the car on the lift today, and sure enough, one of the but ends on my o2 extension had come loose. The tables I just posted are the result of the o2 working correctly now. I actually cleared the LTFT's and drove for about 30 miles before I made those logs. It appears now that I'm running very lean...I'm having a tough time now deciding weather or not to go with a blanket fix using the MAF, and then going back to VE for fine tuning, or if I should just try and continue with the VE. Any insights?

Magic Chicken

iTrader: (1)

I'm new at tuning so I haven't ventured into the MAF side of things yet. I get the LTFT's close with the IFR and use the VE table for fine tuning. But that's just me.

gameover

The PCM uses both the LTFT's and STFT's to determine fueling. The names are exactly what they mean, LTFT is a slow moving fuel correction and STFT is a fast moving fuel correction. The idea of having LTFT's is to make your STFT's vary by small amounts around 0 (ie. the average STFT value should be ideally 0, if your LTFT's are working correctly)

STFT's can be used to tune your fuel as long as you disable the LTFT learning process.

The best way (IMHO) to tune SD is to disable closed loop, disable PE, set your Openloop F/A to a constant (safe) value (to give say 13:1 AFR) and then use the WBO2 as your guide to tuning VE. That way, when enable everything again (and assuming you end up with 0 WOT trims) when you ask for a certain AFR in your various fuel tables, you might actually get it.

HumpinSS

iTrader: (1)

How do you disable the LTFT learning process