MAF tuning via LTFT

[RRRocketMan]

I've got a 2013 Camaro SS manual (LS3) and am trying to find a tool or conversion sheet or something to calculate new MAF values based on LTFT values from my scan log. When I used DHP for my older cars in the past there was a nifty tool that collected all the LTFTs for all the different frequency ranges, averaged them and suggested a new MAF value for each range so you could basically plug n play the new table right into your bin file. Despite my searching I haven't found such a tool for hptuners or the LS3.

I don't have a wideband yet so I want to tune my MAF via LTFTs for now. How are others doing this? Is there a tool or does it have to be done manually in excel and if so, what's the procedure everyone is using?

BTW, will the DHP tool work with the LS3's MAF sensor? Are the frequencies the same? I assumed they would not be.

[umrjmac]

The scan tool contains histograms. I would spend some time reading on the forum and in the documentation about them. What you will most likely do is use LTFT/STFT histograms on a table that maps MAF Hz elements. LTFT and STFT are percentage corrections in fueling, so you can take the table data from the histogram and apply that as percentage difference to the MAF table in your tune.

That is way over simplified, but there are a ton of threads about MAF tuning and a ton of threads about using histograms. I just wanted to give you a push in the right direction.

Good luck!

[RRRocketMan]

The scan tool contains histograms. I would spend some time reading on the forum and in the documentation about them. What you will most likely do is use LTFT/STFT histograms on a table that maps MAF Hz elements. LTFT and STFT are percentage corrections in fueling, so you can take the table data from the histogram and apply that as percentage difference to the MAF table in your tune.

That is way over simplified, but there are a ton of threads about MAF tuning and a ton of threads about using histograms. I just wanted to give you a push in the right direction.

Good luck!

Thank you. With respect, and to be honest, locating basic information on how to use HPT software is rather awkward IMO and I've been struggling just to figure out how to do fairly simple things. Granted, people who already know how to do them will say it's dead simple, and maybe it is, but until you learn it, it's not. So let me see if I understand your train of thought:

I need to take one of the 2D tables that the scanning software uses and define the elements as LTFT values. Then I need to pick one of the axes (since MAF is 1-Dimensional) and assign all the frequency values to it. Then I need to do a road scan and let the table populate, where it should automatically average all the numbers for me, just as it does with the spark table or any other table. Then I need to import that into excel or something and assign a correction factor to each cell based on the LTFT error. For example if the cell for 8 kHz is -2 I might pull 2% fuel. Am I on the right track?

[Iam Broke]

I create a PID of LTFT + STFT for tuning the MAF in closed loop. This takes all correction into account. It's better to keep the fuel trims in CL a bit negative, I shoot for an average between banks of -0.8 to -1.6.

As you posted, the histo would plot a table of LTFT+STFT vs MAF freq.

Don't start scanning until the engine is warmed up and try to drive in a smooth consistent manner.

For WOT open loop you need a wideband O2 sensor.

I prefer hand smoothing rather than using the automated functions such as % half, ect.

Here's my latest scan of the MAF vs. LTFT+ STFT histo from a few days ago... Still a bit rich at idle but with LT's it's hard to get it to settle due to the slower response time.I'll post up some table PID's & histos in a bit.



MAF histo.jpg

[Iam Broke]

Hope this helps a bit for you.





LTFT+STFT PID.jpg

LTFT+STFT PID 2.jpg

[RRRocketMan]

That's precisely what I need. Thank you very much.


Despite it being common knowledge that you shouldn't do this at WOT, can't I do it anyway as a rough estimate? On my grand am, the values were still good enough without me owning a wideband.

[Iam Broke]

The LS3 goes open loop at WOT so it's pointless. Negative fuel trims won't pull fuel but positive will add at WOT. That's why those of us that still enable CL run a bit negative on the fuel trims.

Some try to tune wot using the 02 mv values but it's a recipe for disaster. No narrowband is good for that. I have another PID histo that plots my WB against MAF freq for WOT. I run MAF only above 800 rpm.
I use an Autometer Cobalt WB (lambda, Bosch sensor) gauge in a column pod mount with the 0-4v analog output going into HPT Pro scaled 0.7 to 1.1 lambda. Alternative fuels are simpler to tune in lambda but I learned that way a long time ago.

Your stock file switches over to MAF at ~ 4000 rpm unless you lower it. Gotta switch over lower to tune the MAF.

[Iam Broke]

Here's a pull in 3rd from the same day as before. Target lambda is .82 on corn, richer than pumpgas likes but the O2 MV are in the low 900 mv range. I would never recommend tuning WOT with the NB mv readings at any rate. You can use this for comparison.

Ignore the torque delivered and Dyn cyl air as the tune is scaled 80% for the 95 lb/hr injectors I'm running.



6-28pull.jpg