need help with MAF tuning
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need help with MAF tuning Hi Guys!
Im trying to get my junk dialed in but having some questions about the MAF tune Im doing. Im a noob as far as engine tuning goes but very excited about learning this.
The setup: LQ4 with 862 heads and Elgin 1838P cam, flex injectors 12594512, long tube headers, manual trans.
Since this cam is very similar to the Z06 cam and trying to get a jumpstart, I copied over the VE table from a 2004 Z06 and the graph seemed to make sense.
On the first run, it was lean everywhere, so I added 15% airflow across the board on the MAF table, the weird thing is that it goes above the limit by the end of the scale, but since its just a couple cells, fine.
After a few runs and adding even more air on sections of the MAF table, I noticed that the higher I go, the leaner still is, making the end of the scale be maxed out for more and more cells. I'm sure this cant be right but I'm stuck. I have already double checked the injector data.
Im posting the last run log and the hpt file of my setup, I have made a few small changes to the hpt tune before the log but the issue should still be visible.
Was using the Z06 VE table a bad call and should I start over with the truck table? Should I just try tuning for speed density instead?
Maybe try again using the corvette VE table +5.2631%? (adding volume as displacement difference 5.7 to 6.0)? The problem with this is that some cells go above 100 VE, which Im unsure would make sense on a NA.
Im trying to get my junk dialed in but having some questions about the MAF tune Im doing. Im a noob as far as engine tuning goes but very excited about learning this.
The setup: LQ4 with 862 heads and Elgin 1838P cam, flex injectors 12594512, long tube headers, manual trans.
Since this cam is very similar to the Z06 cam and trying to get a jumpstart, I copied over the VE table from a 2004 Z06 and the graph seemed to make sense.
On the first run, it was lean everywhere, so I added 15% airflow across the board on the MAF table, the weird thing is that it goes above the limit by the end of the scale, but since its just a couple cells, fine.
After a few runs and adding even more air on sections of the MAF table, I noticed that the higher I go, the leaner still is, making the end of the scale be maxed out for more and more cells. I'm sure this cant be right but I'm stuck. I have already double checked the injector data.
Im posting the last run log and the hpt file of my setup, I have made a few small changes to the hpt tune before the log but the issue should still be visible.
Was using the Z06 VE table a bad call and should I start over with the truck table? Should I just try tuning for speed density instead?
Maybe try again using the corvette VE table +5.2631%? (adding volume as displacement difference 5.7 to 6.0)? The problem with this is that some cells go above 100 VE, which Im unsure would make sense on a NA.
Your wideband readings are garbage. Look at the narrowband sensor output. They are working, and are entirely different than the wideband. You should be tuning this in closed loop for almost everything but WOT anyway.
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I was having an entirely different issue with the narrowbands as well, they would not get a proper ground from the PCM to heat up (PCM is a 2005/P59), they would start working somwhat ok only after the engine was well warmed up. The engine was pretty warm in this run.
The wideband is showing lean when your narrowbands show rich. When your narrowbands show just slightly lean, your wideband goes to an almost maximum lean reading. Is this a real AEM, or an Amazon purchase? When you tune in closed loop, you use the fuel trims for tuning and ignore the wideband. Unless you plan to always leave the computer in open loop, the trims are what the computer will try to correct to anyway.
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The wideband is showing lean when your narrowbands show rich. When your narrowbands show just slightly lean, your wideband goes to an almost maximum lean reading. Is this a real AEM, or an Amazon purchase? When you tune in closed loop, you use the fuel trims for tuning and ignore the wideband. Unless you plan to always leave the computer in open loop, the trims are what the computer will try to correct to anyway.
Any chance I could have set it up wrong?
I am going to hotwire the ground on the o2's and get new readings today. I also had a vacuum leak by the throttle body gasket before and thought it was sorted, but will check that again to discard this possibility.
Last edited by robbieLQ4; Nov 16, 2025 at 02:39 PM.
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Verdad Gallardo I did not even look at your log settings to see if you were running an analog input in, using serial in, or using CAN in. If using analog input in, then it is very possible it could be set up wrong. Also, do some reading on case grounded and isolated ground narrowband sensors. That may have an impact on how you decide to check/fix any wiring issues with them.
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I did not even look at your log settings to see if you were running an analog input in, using serial in, or using CAN in. If using analog input in, then it is very possible it could be set up wrong. Also, do some reading on case grounded and isolated ground narrowband sensors. That may have an impact on how you decide to check/fix any wiring issues with them.
Where is your wideband installed? If it is behind the narrowbands and in a spot where an exhaust leak could be letting fresh air into it, that could explain the lean readings. Otherwise I would suspect a defective unit, although other possibilities would still need to be ruled out.
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These are the readings after grounding the narrowband, first run as it was, second run with the vette MAF table +10%, third run with the vette MAF +5.23%.
note: My wideband is on bank 2.
Looking at the last, does it seem like I might have a fueling issue between banks aswell?
The engine seems to run smoother with this leaned out file compared to before, rpms would dip on return to idle quite a bit before, I thought it could be due to the scaling of the MAF table, as I was adjusting cells individually trying to match the lean/rich indicated by the wideband.
note: My wideband is on bank 2.
Looking at the last, does it seem like I might have a fueling issue between banks aswell?
The engine seems to run smoother with this leaned out file compared to before, rpms would dip on return to idle quite a bit before, I thought it could be due to the scaling of the MAF table, as I was adjusting cells individually trying to match the lean/rich indicated by the wideband.
Last edited by robbieLQ4; Nov 16, 2025 at 04:17 PM.
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Where is your wideband installed? If it is behind the narrowbands and in a spot where an exhaust leak could be letting fresh air into it, that could explain the lean readings. Otherwise I would suspect a defective unit, although other possibilities would still need to be ruled out.
Give up on the wideband for now. It obviously has issues. It may just need to be recalibrated, but I have no idea on that. Turn on closed loop and tune from the fuel trims. However, before doing that check your fuel pressure under load. Every time you mash the throttle it appears to be leaning out badly. I would not be surprised if you have a fuel pressure problem to go along with the other issues. You can't tune out mechanical problems.
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Give up on the wideband for now. It obviously has issues. It may just need to be recalibrated, but I have no idea on that. Turn on closed loop and tune from the fuel trims. However, before doing that check your fuel pressure under load. Every time you mash the throttle it appears to be leaning out badly. I would not be surprised if you have a fuel pressure problem to go along with the other issues. You can't tune out mechanical problems.
I reenabled all trims and others settings i had turned off, DFCO, etc. Tune file is using the Z06 MAF(and Z06 VE) + 5.23% across the board.
first file is driving right after the change, second file after stopping, shutting engine off and back on, then driving back.
how can I tune for trims? disable LTFT and adjust basing on the logs STFT ?
If it turns out you have fuel pressure under load, which I highly doubt, it is far enough off to start by using stft+ltft to adjust fueling. You can log them individually and adjust for either one if you wish, although I would adjust for long term trims once it is close. The closer you get, the more you can manually smooth your maf and VE tables (tune both individually) and mathematically start filtering out non-steady state info from the logs. Remember to look at the table graphs, as that makes it easier to identify spikes of erroneous data to smooth out as you are copy/pasting error corrections.
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If it turns out you have fuel pressure under load, which I highly doubt, it is far enough off to start by using stft+ltft to adjust fueling. You can log them individually and adjust for either one if you wish, although I would adjust for long term trims once it is close. The closer you get, the more you can manually smooth your maf and VE tables (tune both individually) and mathematically start filtering out non-steady state info from the logs. Remember to look at the table graphs, as that makes it easier to identify spikes of erroneous data to smooth out as you are copy/pasting error corrections.
Not sure if you looked, but Im starting to suspect maybe theres an issue with my injector settings, particularly pulse width, as its not keeping up with higher rpm or fast changes in rpm. I found two different settings for Flex injectors, one from a spreadsheet that somebody put together and another with data I extracted from P59 PCMs with flex injectors (but I think these cars came with a different injector part #). and used what the spreadsheet said it was for the 12594512, dont recall if I ran with the other settings.
Wideband still reads lean 15AFR and up at all times basically.
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If it turns out you have fuel pressure under load, which I highly doubt, it is far enough off to start by using stft+ltft to adjust fueling. You can log them individually and adjust for either one if you wish, although I would adjust for long term trims once it is close. The closer you get, the more you can manually smooth your maf and VE tables (tune both individually) and mathematically start filtering out non-steady state info from the logs. Remember to look at the table graphs, as that makes it easier to identify spikes of erroneous data to smooth out as you are copy/pasting error corrections.
I just recalled my wideband is installed on the exhaust right after the long rube headers junction to the Y pipe, so there might be air leaking in from that junction, I will look into ways to better seal it.
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If it turns out you have fuel pressure under load, which I highly doubt, it is far enough off to start by using stft+ltft to adjust fueling. You can log them individually and adjust for either one if you wish, although I would adjust for long term trims once it is close. The closer you get, the more you can manually smooth your maf and VE tables (tune both individually) and mathematically start filtering out non-steady state info from the logs. Remember to look at the table graphs, as that makes it easier to identify spikes of erroneous data to smooth out as you are copy/pasting error corrections.
I have tried the tune looking at LTFT+STFT but I ended up running rich, lots of exhaust smell too especially with the trims enabled. I swapped the stock o2 with the wideband (bank 2, the wideband was after a exhaust junction and the stock o2 was right at the long tube headers). There is a noticeable difference in readings, so probably getting air in the junction, messing with the readings.
I did a couple of runs and retuned the MAF, smell seems better and readings look more consistent but still going off the chart at the end of the MAF if you extrapolate the 15%+ air it asks for. Note: Long tube headers end is 3in and the y-pipe is 2x 2.5in junction to a 3in.
Quick question, do the stock o2 readings on bank 1 look ok to you based on the new wideband readings? b1 and b2 now differ quite a bit as the b2 is installed after a junction that seems to be letting air in.
Last edited by robbieLQ4; Nov 30, 2025 at 11:52 PM.