Why aren?t my VE adjustments having any effect?

[JakeRobb]

For context: I am a first-time hobbyist tuner, working on tuning a cammed, 24x LS3 in my 2002 Z28 with a P01/0411 loaded with the RTT OS. I have applied the correct injector data, configured the cylinder volume, I have the MAF, DFCO, and PE disabled. I did not disable LTFT or STFT. I have reset the LTFTs since the last time I wrote the calibration. I'm now trying to work on fueling adjustments via the VE table. It's way too rich in the low RPM range.

Since I'm totally new to this, for now I'm focused on the couple cells involved at idle. Yesterday morning (30F), I went out, started a log, and let it idle up to operating temp. When it got warm enough to go closed-loop, I observed it starting to make STFT adjustments, and I can also see those migrating over to long-term as expected. Given enough time, the LTFTs settle in around -16%, with and additional negative 5-8% in the STFTs that don't seem to go away -- I'm guessing that the LTFTs are maxed out and can't get any larger? Or maybe I'm just not being patient enough -- but whatever, that's not the point of this post.

Since the trims are negative, I know the numbers in the VE table are too high. I open up the RTT interface, activate the RAM tables, and let it load in the values (which have the changes I made and wrote to the PCM earlier, so I think I'm at least doing that part right). Then highlight the two cells where idle seems to settle, plus the ten adjacent cells (to allow for interpolation), and tap the minus key a bunch of times. I've taken the target cells from ~50 down to as low as 10, but nothing changes.

My expectation is that, after several seconds, I should start to see those changes reflected in the STFTs (they should drift into the positive), but that never happens, no matter how much I change these values. I can decrease them by 80% -- nothing changes. I've waited several minutes, still nothing. The NB02 sensors continue to oscillate like normal. I've reset LTFTs while it idles; it begins trimming negative immediately and ends up right where it was before.

I've also tried applying my changes to the Primary VE table and then writing the calibration. It still doesn't seem to be making any difference.

After some googling, I learned about secondary VE tables, and figured that must be just what I need -- that I must be making changes to the wrong table since the MAF is disabled. But I can't find a secondary VE table anywhere. I know some OSes don't have one, and I'm led to believe that the 2001+ F-body OS doesn't -- so I'm guessing that's the case here.

Do I have a secondary VE table and I just can't find it? Am I coming at this all wrong? Have I failed to configure things correctly for this phase of tuning and the PCM is somehow compensating for my changes on the fly and ending up where it was before?

For clarity: the only thing I did to disable the MAF was to set the high cutoff to 200rpm. I have seen some people say that's all that is needed, and others say you need to set a dozen other things as well. Maybe that's my issue? My MAF is definitely not calibrated correctly (yet -- I intend to do VE first).

Log file: jake-robb-log.hpl
Tune file: jake-robb-tune.hpt
Scanner config: jake-robb-config.cfg

Thanks!

[SiriusC1024]

Gotta fail the MAF.

Engine Diag>Airflow>MAF Frequency Fail High to 0Hz
...>DTC's set P0101, P0102, P0103 to MIL on First Error.

[edcmat-l1]

MAF is not failed. Wherever you got your info from about how to do that is completely wrong. You have to set the fail to zero or single digit and make sure it sets a P0103 code. If that code isn't set, it's not in speed density. You also need to copy/paste the high octane spark table to the low octane. Once you fail the maf it will resort to the low octane table. I go a bit further and zero the MAF table so it can't reference it even for any other calcs.

[SiriusC1024]

For clarity: the only thing I did to disable the MAF was to set the high cutoff to 200rpm.

That's actually for MAF tuning. It forces dynamic airflow to be calculated based on filtered MAF. Before, anything below 4000 used the VE table for throttle changes in order to predict airflow, MAF during stable throttle.

[SiriusC1024]

Hey Jake which of those two in your sig is more fun to drive?

[SiriusC1024]

Sorry for all the posts, but a few things about the fueling before you get carried away doing the airflow models.

- Double check the injector data. Blindsquirrel made a nice spreadsheet that converts Gen IV to Gen III data. Looks like you're running 12576341 injectors. It's different than than what's listed here at post #39:
https://forum.hptuners.com/showthrea...pository/page2

- Idk about the MinPulse in that file, though. From the SPA looks like it should be 0.729ms instead. Then from there adjust Transient>Min Fuel Milligrams to .023 (MinPulse/31.12 = Min Fuel Mg)

- Adjust injector timing. Google 'Summit Valve Timing Calculator' then input your cam data. Make sure duration is for 0.050 lift and not 0.006 like is listed for some Gen IV cams. Take the data from the calculator and put it into the attached spreadsheet.

[JakeRobb]

Hey Jake which of those two in your sig is more fun to drive?

They're both a riot, but very different. The Z28 is my personal preference, although the engine swap has been in the works for a long time and I haven't driven it in years! (I did back it out of the garage the other day.)

The Z28 is an excellent all-around performer. Acceleration, braking, cornering -- all great (it was decent stock, but I've done a ton to improve those aspects!). It's tight and responsive. It's raw and rough, lacking the "refinement" that makes driving fancy cars honestly kinda boring to me. My cousin has a Cayman GTS. It's fantastic, but also boring. It's too perfect; it just does what you tell it with no effort. The Z28's cornering limits can't match the Cayman's, but it is not boring! It rewards driving skill and penalizes mistakes.

My favorite thing about driving the GN is when you're sitting at a light, it goes green, and you floor it -- the car starts to roll maybe 5-10 feet before the turbo is spooled, and then it blows the tires off. Makes me giggle every time. And, of course, the addictive rocket-thrust sensation you get when accelerating with boost. It leaves a lot to be desired in the cornering and braking department; it has a decent shock+spring package, but I plan to upgrade to a slightly larger wheel and tire so I can accommodate a larger brake rotor (currently limited to 11"), and also to add some decent swaybars.

[JakeRobb]

Sorry for all the posts, but a few things about the fueling before you get carried away doing the airflow models.

Thanks for digging in and checking that stuff!

- Double check the injector data. Blindsquirrel made a nice spreadsheet that converts Gen IV to Gen III data. Looks like you're running 12576341 injectors. It's different than than what's listed here at post #39:
https://forum.hptuners.com/showthrea...pository/page2

That does appear to be the right injector p/n. I'll copy that data.

- Idk about the MinPulse in that file, though. From the SPA looks like it should be 0.729ms instead. Then from there adjust Transient>Min Fuel Milligrams to .023 (MinPulse/31.12 = Min Fuel Mg)

Where does 31.12 come from?

- Adjust injector timing. Google 'Summit Valve Timing Calculator' then input your cam data. Make sure duration is for 0.050 lift and not 0.006 like is listed for some Gen IV cams. Take the data from the calculator and put it into the attached spreadsheet.

Oh, I didn't even know this was a thing! Thank you.

[JakeRobb]

Followup questions, to boost my understanding of how the system works:

I'm under the impression that, normally, the VE table is used when the MAF is not operational or when RPM exceeds 4000.

I thought that, by adjusting the high cutoff to 200rpm, the VE table would be used throughout the range. Can anyone explain why that's not the case? What does change when I adjust the high cutoff?

Does the PCM use the VE table for anything at all when the MAF is enabled and functioning and RPM is below the cutoff?

[kevin87turbot]

Followup questions, to boost my understanding of how the system works:

I'm under the impression that, normally, the VE table is used when the MAF is not operational or when RPM exceeds 4000. You've got that backwards...The MAF is being used when RPM exceeds 4k...or in your case 200rpm. However...the ECM does refer to the VE for transient fuel calcs. If you enter 0 in the MAF high freq fail value, and change P0101,2 and 3 to MIL on first error, it'll force VE mode only.

I thought that, by adjusting the high cutoff to 200rpm, the VE table would be used throughout the range. Can anyone explain why that's not the case? What does change when I adjust the high cutoff? You'll need to change it to a high value...something higher than your rev limiter.

Does the PCM use the VE table for anything at all when the MAF is enabled and functioning and RPM is below the cutoff?

[JakeRobb]

Followup questions, to boost my understanding of how the system works:

I'm under the impression that, normally, the VE table is used when the MAF is not operational or when RPM exceeds 4000.

You've got that backwards...The MAF is being used when RPM exceeds 4k...or in your case 200rpm. However...the ECM does refer to the VE for transient fuel calcs. If you enter 0 in the MAF high freq fail value, and change P0101,2 and 3 to MIL on first error, it'll force VE mode only.

I thought that, by adjusting the high cutoff to 200rpm, the VE table would be used throughout the range. Can anyone explain why that's not the case? What does change when I adjust the high cutoff?

You'll need to change it to a high value...something higher than your rev limiter.

Fixed that for you. Now, to address something you said:

You've got that backwards...The MAF is being used when RPM exceeds 4k...or in your case 200rpm.

So, under normal operation with a factory tune, the MAF is irrelevant below 4000rpm?

[horsepowerguru427]

Followup questions, to boost my understanding of how the system works:

I'm under the impression that, normally, the VE table is used when the MAF is not operational or when RPM exceeds 4000.

I thought that, by adjusting the high cutoff to 200rpm, the VE table would be used throughout the range. Can anyone explain why that's not the case? What does change when I adjust the high cutoff?

Does the PCM use the VE table for anything at all when the MAF is enabled and functioning and RPM is below the cutoff?

High RPM Cutoff actually refers to the VE table. At what point is it going to CUTOFF the VE data and ONLY USE MAF. So, Raising the limit to, say 8000RPM will make reference the VE table and not the MAF up to 8000RPM(for arguement sake) but you also have to set your MAF fail Freq LOW (like edcmat said) i usually use something like 100 or 400. Also you need to set DTC code 101,102,103 to MIL on 1st err so the PCM recognizes that that MAF is "faulty" and it references ONLY the VE table.

[JakeRobb]

Okay, so, putting everything in this thread together, here's my to-do list. Please let me know if I missed anything:

* Fix injector data (details TBD)
* Set MinPulse to 0.729
* Set Min fuel milligrams to 0.023
* Adjust injector timing based on my cam data (details TBD)
* Change MAF high cutoff to 8000.
* MAF fail high frequency to 0
* DTC P0101 -> MIL on first error
* DTC P0102 -> MIL on first error
* DTC P0103 -> MIL on first error
* Copy the high-octane spark table to low octane
* Zero out the MAF table

[JakeRobb]

Cam timing calculator results:

Screenshot 2023-12-31 at 1.33.10 PM.png

[horsepowerguru427]

Okay, so, putting everything in this thread together, here's my to-do list. Please let me know if I missed anything:

* Fix injector data (details TBD)
* Set MinPulse to 0.729
* Set Min fuel milligrams to 0.023
* Adjust injector timing based on my cam data (details TBD)
* Change MAF high cutoff to 8000.
* MAF fail high frequency to 0
* DTC P0101 -> MIL on first error
* DTC P0102 -> MIL on first error
* DTC P0103 -> MIL on first error
* Copy the high-octane spark table to low octane
* Zero out the MAF table

Yeah, Pretty much covers it. I usually make sure COT and DFCO are off while collecting data as well, so theres no unexpected fueling changes in the background im unaware of. Stay out of PE and WOT areas and you should be good to tune. Be sure and filter data so youre not adding junk data to your tune

[JakeRobb]

I got the injector data I used from post #2 in this thread. Someone had already plugged the data into the spreadsheet and converted it.

[JakeRobb]

Yeah, Pretty much covers it. I usually make sure COT and DFCO are off while collecting data as well, so theres no unexpected fueling changes in the background im unaware of. Stay out of PE and WOT areas and you should be good to tune. Be sure and filter data so youre not adding junk data to your tune

I already have DFCO and PE disabled. I've just turned off COT as well. I am not planning on using WOT as it's currently too cold to drive the car anywhere (below safe temps for summer tires) -- I'm just idling and revving in my driveway, so I can't hit most of the map. I probably won't even bother with RPMs over 4000 or so. The rest will have to wait for warmer weather, or until I can get some time on a dyno. I could hit a bit more if I was willing to burn out my clutch...

For now, I'm just going to mess with numbers using RTT. Once I can drive it, I have a more robust long-term plan in mind. I'll be charting LTFT+STFT, showing data only where count > 100. I'm thinking I'll do an initial pass using Paste Special -> Multiply by % to get things close, then a few more passes as needed with Multiply by % - Half. Feedback appreciated! In particular: should I be using Average or Last values? Leaning towards Last, since the PCM should be refining the trim values as I drive, and that should be more effective than Average.

[JakeRobb]

Okay, I've done everything except the injector timing. I'm not sure which numbers from the Summit calculator go where in the spreadsheet...?

Screenshot 2023-12-31 at 2.47.30 PM.png

[JakeRobb]

Looked again and now I think I see -- I just have to copy the bottom four values from the calculator into rows 13-16 of the spreadsheet. Then which row(s) do I copy into the tune, and where does it go?
Screenshot 2023-12-31 at 3.31.17 PM.png

[horsepowerguru427]

Average, however, you can use the histo C button for count.jpg "C" button above the histo, you will see the numbers change. This tells you how many hits you had in each cell. The low numbers need to go away. Thats not accurate data. Doing it this way will give you very accurate average numbers in cells and eliminate the low hit cells. You can input what data you have and interpolate between known good cells in the VE table Interpolate VE areas after paste.jpg of data that you collected (like i circled) which will end up looking something like this VE after interpolate.jpg which gives a little more accurate data in the altered area. I usually dont smooth much, maybe between cell boundries that i changed vs didnt change. but i never do an OVERALL SMOOTH.