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Stft and Wideband conundrum.

Road Tuning

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Alrighty guys back for more info

I got a LS swapped 87 S-10

2001 Silverado 4.8 with Isky triple 12 cam

Cam specs 212.212, .561/.561,110 LSA

Got my maf tune pretty squared away I feel. Less than 1% in pretty much all areas of the curve. Now, when i switched back to closed loop and enabled stft's, I'm getting almost exactly opposite readings, is this normal? When in gear under load , stfts read .6v+ indicating 20%+ rich . In the same areas my wideband is reading 20%+ lean. How is this possible? And is it normal to have them read opposite of each other? Do I just continue on to the VE tuning now that my scaling looks good and worry about the closed loop operation later?

Normally, I consider a Fuel Trim the amount of fuel change. So a +20% STFT would be required to correct a 20% lean condition.

So what you're saying is that it looks normal? They are just the inverse of each other?

Cause I see what you're saying but that doesnt really answer my question. I get that if I had a positive stft fuel trim it would require an addition of 20% of fuel. But my stft's are negative indicating a rich condition but my wideband is reading the exact opposite, so whatever my STFT'S are saying (rich) my wideband is saying that percentage lean


clear your KAM.

Thank you, you're talking about the Keep Alive Memory correct? Haven't seen it in the scanner, but I read that you can just unplug your battery for a bit and itll reset?

He wants you to reset the long term fuel trims, because short term fuel trims are adjusted on top of long term fuel trims.

Gotcha! Thank you Raymond! I can always count on you to come in with good knowledge! Good to see you again. I have been resetting the ltft when I'm logging just about everywhere to try and rule that out. I did flash a new OS into my computer that resembled more what my engine stock is. And I'm amazed at how much of a difference it has made. In the ease of tuning. Maf only took three or four iterations to get it dialed in and I've started on my Main VE table. New OS has no secondary table, so I assume just scale the maf and then do the VE, then go back and repeat to clean things up?

So what kind of stft + ltft are you seeing now? You certainly want to be within +/- 10%, preferably +/- 5% . You don't necessarily need to clear ltft's all the time, it kind of depends how far off 0 it's learning.

Alrighty, getting some logs together for you guys. Need to see what I'm doing wrong here. Will update in a bit with tune post, and some logs. I do not have rear O2's on this setup, just the front, and a wideband after that but before the cats.

Thanks again

Alrighty guys, quick update got some logs and shiz done before work. I am in the mountain time zone in the USA, I'll be posting my info around 500 pm my time. Catch up with you guys in a bit

Alrighty once again

Gonna post up MAF OL scans and tune:

Attached Files

Now for MAF CL scans and tune:

Attached Files


This is my fueling stuff after one iteration.

Attached Files


Attached Files

Thats everything i got before work today. looking at my MAF OL, looks like i still have a lot of work to do scaling wise. but any and all advice, criticism, whatever, I'll take it. Id really like to get this truck running well. as well, I noticed that one of my sensor 1's is reading significantly richer than the other side. but if you guys are willing to go through my garbage pile of info and tell me what all im messing up ill be making changes and getting it done right! thanks guys! Even if i gotta start over i guess, itll only be like the 15th ive scrapped a tune and started over, so no worries if thats what you think!

Okay here we go... Decided to just start over on the MAF scaling after work. made sure the truck was warmed up, drove her for a bit, reset fuel trims (just in case) and then started logging, I did a few logs and put together a new scale, seems a little smoother like the factory tune, and there definitely isn't as much airflow at the top end as this one. maybe i was telling it there was way more air flowing at the top end than what it had. I don't know, but I'm going to post up this new scale and the stock file so hopefully you guys can compare it and let me know what you think. Looking at MAFLETSGO compared to MAFletsgo2try, i can see that i was definitely way off the mark there. Dear lord. Back to the drawing board. Im gonna get this scaling thing down, then get my VE tuned then pass my sniffer test and just be happy with the truck for a bit til i get a few more things in order.

OOH! One more thing, Ive noticed that my Hz values in gear lets say 3375Hz says .02% or what have you lean, but that same 3375Hz says rich at idle. is that just because there isnt any load on the engine?

Attached Files

Quick update this morning, uploaded new maf scale and it fired right up, like right up. And I did a scan for codes and I got a P0155. Bank 2 sensor 1 rich condition. May have found my issue?

Got my daughters dance recital to go to then more scaling to see what's up

Did some more scaling after my daughters dance recital.

gonna post the tune before i change it, the logs i took, and then the "after" if you will.

Heres the tune and log:

Attached Files

And here is the tune after changes:

Attached Files

Can you post screenshots of any particular datalog sections or tables you would like us to look at?

Yessir I sure can! been working more on the scaling. As stated I did get a rich code from the Bank 2 sensor 1 sensor, so I think that has something to do with my STFTS being so off. Im going to post up another MAF scale, id like to have you guys look at my scaling at 5500hz +. Cause it seems the closer I get to 0% up top, sometimes it starts sounding like Im asking it of too much air? It almost sounds like its hitting a rev limit if that makes sense? ill post it up in a bit, and you guys can let me know what you think.

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