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Thread: need help with ve and maf tuning

  1. #1
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    need help with ve and maf tuning

    I'm trying to get the fuel trims squared away on my '01 Vette. It has a Magnacharger and a 220/226 cam. The trims were running around -14 to -20. So, I failed the maf, and after 4 or 5 runs using the copy paste special to the VE table got them down to around -4. So, I re-enabeled the maf and made a run -- now the maf table is calling for -15 in all cells I hit, and it was around 0 prior to Ve tuning!! So I did a copy paste special to the maf table and made another run. Its still calling for -15, plus now the trims are going positive. What now, get the maf tuned out and go back to the trims via the VE table, or what?? I feel like I'm going in a big circle.

  2. #2
    Senior Tuner 5_Liter_Eater's Avatar
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    A few things here; When you say 'runs' are you going WOT? If so, you should know that once you enter PE mode your fuel trims lock, so you can't tune PE/WOT with fuel trims. O2 mV's? Maybe for a stock motor but certainly not for a blown one. So you can't tune WOT without a wideband, VE or MAF.

    If you're tuning the VE table via disabling the MAF and you don't have the 2 or 3 bar SD OS upgrade then you are rolling the dice when going WOT. Your 105 kPa row is all you have to work with from atmospheric to full boost. Only tune your VE table for part throttle/non-PE mode. The PCM uses all MAF after 4000 RPM's anyway.

    Sounds like you got your VE trims in line somehow though. Have you been copying in every other row of the primary VE to the sedondary VE? The PCM works off the secondary VE table when the MAF fails so after each copy and paste into the primary VE, copy every other row into the sedondary VE. Also the PCM defaults to the low octane map when the MAF fails so you need to temporarily copy the high octane timing map into the low octane map.

    I don't understand what you mean by, "it's still calling for -15 plus the trims are all positive.". Maybe what you are doing is re-enabing the MAF but still making changes to the VE table? If so this will have no result. You need to be making changes to the MAF table and remember, fuel trim tuning is useless and dangerous in PE.

    HTH, let me know if I have made any wrong assumptions.
    Last edited by 5_Liter_Eater; 05-09-2007 at 01:02 PM.
    Bill Winters

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  3. #3
    Senior Tuner Russ K's Avatar
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    The 2001 & up PCM only has a primary VE table. Leave the VE table stock and tune the Maf table. Find one of my Maf config files, the STFT & LTFT histograms will then help tune the Maf. You really need to get a wideband to tune your car.

    Russ Kemp

  4. #4
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    I am being careful to stay in out of wot while making my "runs". What I meant about the "still at -15" comment was after I did the first paste special to the maf table when it was showing -15, I made another run and it still showed -15 and the fuel trims were now going positive, where as the trims were around -4 on the preceeding run.
    I do have an LM1 for wot tuning, but I was doing the ve and maf tuning with the stock narrow bands and stft's, I think!! That is, today after tuning, I was wondering if I had the the maf table properly set up. I do have a pid for 'wide band o2' set up in the table, and I noticed while tuning today that it showed about 12.6 the entire time. the the wide band is not currently installed?? I wonder if the maf table was taking "input" from this "ghost" wide band??
    The car runs really well, I've got the wot set at about 11.0 via the LM1 as my maggie is a non intercooled version, and when I tried to lean it I got knock retard. Keeping it at 11.0 allowed me to run a decent spark advance program (around 23 degrees for wot) which really made a difference in power.
    I do appreciate the help.
    Last edited by vetteman3; 05-09-2007 at 06:53 PM.

  5. #5
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    Ok, I kind of figured it out. On the scanner program, table view, for some reason after the LM1 pid it shows an AF of 12.4 while scanning engine idling, closed loop. On the graph view under wide band O2 it has a straight line at 12.4, and the LM1 is not installed!! The air fuel error is listed as -15% in the table view, as was the maf table in hist #8. When I multiply 14.6 x .85 (the correction for the -15) I get 12.4 - go figure. So, I'll just re-install the wide band and re-do the maf table!! So now the question is, what's up with this 12.4 indication for a wide band that is not present for duty??
    Last edited by vetteman3; 05-09-2007 at 07:36 PM.

  6. #6
    Tuner 2000C-5's Avatar
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    Quote Originally Posted by vetteman3
    Ok, I kind of figured it out. On the scanner program, table view, for some reason after the LM1 pid it shows an AF of 12.4 while scanning engine idling, closed loop. On the graph view under wide band O2 it has a straight line at 12.4, and the LM1 is not installed!! The air fuel error is listed as -15% in the table view, as was the maf table in hist #8. When I multiply 14.6 x .85 (the correction for the -15) I get 12.4 - go figure. So, I'll just re-install the wide band and re-do the maf table!! So now the question is, what's up with this 12.4 indication for a wide band that is not present for duty??
    If you have a wideband, you need to use it to do all your tuning. Don't use the fuel trims for anything but to double check yourself when you are completely done.

    Use this to do your VE, MAF and WOT tuning.

    For VE Tuning with a wideband,

    You need to:

    - set the Engine/Fuel Control/OL & CL/Closed Loop Closed Loop Enable/ECT vs IAT to 284* across the board. This will put you in open loop along with setting the MAF fail freq to 0.

    - on the same page as above, you want to disable LTFT

    - also on this same page, in Open Loop/EQ Ratio, set all to 1.00 or I just change the ones from 140* and up to 1.00 (this will command 14.63 or stoich)
    This step can be done several ways too. You can leave it as is if you want or change it to 1.13 which will command 13.0 AFR, it doesn't really matter what you are commanding, because the % error will still be the same. After going back to Closed Loop you won’t use this table anymore.

    - in Engine/Fuel Control/Fuel Cutoff set DFCO enable temp to 284*

    - in Engine/Fuel Control/COT, Lean Cruise set COT to disable

    - in Eng. Diag/Airflow set MAF fail freq to 0 (you should also unplug the MAF if you can. If you are driving a 2001 and newer C-5 , the IAT is wired into the same plug, so you can’t unplug the MAF without doing some rewiring. They are seperate in the earlier C-5s)

    - Now go log. Make sure you log VE for Actual AFR, Commanded AFR, and AFR Percent Error. I log first and then change the cell hits required to 25 for the % Error histogram.

    - Right click/Copy the entire % Error histogram.

    - Open Editor, highlight, right-click and use the “paste special/multiply by %” to the Engine/Airflow/General Airflow/Main VE/Primary table. As you get closer to 0, start using “paste special/multiply by –half”.

    - Then, if you have a 1997-2000 C-5, copy the even numbered MAP lines to the secondary VE table by using the copy/paste method. Save and "write calibration only" to the PCM. Drive and see where you are.

    Wash, Rinse, Repeat until your VE tables are in line. Your AFR % Error histograms should be as close to 0 as possible. It should only take 3-5 runs.

    After this, it is time to tune MAF/WOT. Reset the MAF fail back to 14000 (leave everything else as is for now) and modify the MAF Calibration/Airflow vs. Frequency tables the same way you did for the VE tables, except you will use MAF vs Output Freq (Hz) histograms instead of the VE histograms. The MAF Calibration table is just above the VE table(s) on the same page in Editor.

    After tuning MAF/WOT, set all of the above tables back normal and you’re done. Time to move on to spark, transmission settings or whatever you decide to do next. Have fun.
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  7. #7
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    Thanks for all the help, but I have to ask a couple of questions.
    What is the advantage of tuning the MAF table instead of the VE table for part throttle fuel tuning, like Russ K advised?
    And What is the advantage of tuning the MAF table instead of the PE table for WOT fuel tuning, like 2000C-5 suggested?
    Its too bad GM has to make things difficult and have a PCM program with multiple tables which have overlaping authority.
    Last edited by vetteman3; 05-11-2007 at 09:22 PM.

  8. #8
    Senior Tuner Russ K's Avatar
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    The VE table is used when there is a Maf failure and for a sanity check to determine if there is a Maf failure. The VE table also provides a transient correction. Your Magnacharger will exceed your 1 bar VE table anyway.

    Just tune the Maf table only, I do it this way all the time. The C6 Z06 doesn't even have a traditional VE table, these cars are all tuned with the Maf table & PE.

    Russ Kemp

  9. #9
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    Thanks for that explanation, but what about the EQ ratio table? Is this used during OL, or CL , or during PE or what?
    And what about the Injector Flow Rate table, when would this table be used for tuning?
    And on the PE table, why tune the MAF instead for WOT tuning?

  10. #10
    Tuner 2000C-5's Avatar
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    Quote Originally Posted by vetteman3
    Thanks for that explanation, but what about the EQ ratio table? Is this used during OL, or CL , or during PE or what?
    The OLFA table is a fuel adder based on Engine Coolant Temp. It is only referenced in Open Loop.

    Quote Originally Posted by vetteman3
    And what about the Injector Flow Rate table, when would this table be used for tuning?
    The injector flow rate table is not used for tuning. You set it for the actual size of the injectors in your car and leave it alone.

    Quote Originally Posted by vetteman3
    And on the PE table, why tune the MAF instead for WOT tuning?
    The PE table is an adder to the Actual AFR. If you have tuned the VE correctly, your Actual AFR should be ~14.7. You choose the numbers in the PE table based on this. If you want your WOT AFR to be 11.0, then you put a 1.34 in the PE table (14.7/1.34 = 11.0). When you log WOT and the AFR is not 11.0 (and VE is correct at 14.7), it means that your MAF is not reading the correct airflow. You adjust the MAF table to get the Commanded 11.0 AFR.
    Last edited by 2000C-5; 05-12-2007 at 09:48 AM.

  11. #11
    Tuner 2000C-5's Avatar
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    Quote Originally Posted by Russ K
    Just tune the Maf table only, I do it this way all the time.
    Russ Kemp
    More on this, Russ. Is this a FI thing only? You're saying to just adjust the airflow readings to get the Commanded? I assume you would do this in CL, otherwise, AFRs would be all over the place?

  12. #12
    Senior Tuner Russ K's Avatar
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    Since I install the wideband in place of the O2B2S1 (right front), the car is in open loop. Then I set up the open loop table to 1.00 at operating temp. Also on some vehicles, the stoich needs to be changed to 14.68. Then disable the AIR pump and DFCO (some vehicles need to have more than just the enable temp raised).

    Now the commanded AFR will be 14.68 when not in PE and what ever you set the PE to be (when in PE). Reset the fuel trims. Then just use my Maf tune config file and copy the Maf AFR% Error histogram & paste it to the Maf table. Command 2nd gear with the VCM controls, or use 3rd gear if a manual trans when doing the WOT scan. This works very well, and I do the same on NA engines as well.

    Russ Kemp

  13. #13
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    Hey - nice to have such an informative discussion between us Corvette Guys!! Ok, its starting to sink in now and make some sense. Too bad this kind of information isn't in the help files and such?!
    So, the OLFA table work as a choke on a carb to richen up the mixture a bit when cold. My table on the car I'm currently working on (the blown '01) has fuel added throughout the entire table. I feel it should be (after tuning) all 1.0's in the normal operating temp range and hotter, and maybe a bit richer when cold (>1.0)to help driveability - correct?
    And if I understand it correctly, the PE table works hand in hand with the MAF table, modifing its "readings" to achieve the desired AFR. And so I guess you could either modify the PE table or the MAF table to get the desered end result, or in my case 11.0 AFR when WOT - correct?
    This car had considerable tuning from a "Top Tuner" in Texas using LS1 edit before I bought it last year. On the way home to Alabama the SES light came on so we returned to his shop. Fuel trims were high (-14), so they cut back the injector flow rate table to correct this problem, and went the other way on the PE table so as to not change WOT fuel. Well, fuel trims are still runnning around -14, but not for long!!

  14. #14
    Tuner 2000C-5's Avatar
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    Quote Originally Posted by vetteman3
    Hey - nice to have such an informative discussion between us Corvette Guys!! Ok, its starting to sink in now and make some sense. Too bad this kind of information isn't in the help files and such?!
    So, the OLFA table work as a choke on a carb to richen up the mixture a bit when cold. My table on the car I'm currently working on (the blown '01) has fuel added throughout the entire table. I feel it should be (after tuning) all 1.0's in the normal operating temp range and hotter, and maybe a bit richer when cold (>1.0)to help driveability - correct?
    You can just leave it stock below 140*. The car is below 140* for just a few minutes.

    Quote Originally Posted by vetteman3
    And if I understand it correctly, the PE table works hand in hand with the MAF table, modifing its "readings" to achieve the desired AFR. And so I guess you could either modify the PE table or the MAF table to get the desered end result, or in my case 11.0 AFR when WOT - correct?
    Not really, like I said, the PE table just adds a percentage of fuel to the stoich (14.7) to get the desired AFR at WOT, that's it, there is no "tuning" involved. Just do the math and set it for the 11.0:1 AFR that you want to run.

    When you do your WOT runs and the Actual AFR doesn't match the Commanded AFR (11.0), you adjust the MAF table until they match.


    Quote Originally Posted by vetteman3
    This car had considerable tuning from a "Top Tuner" in Texas using LS1 edit before I bought it last year. On the way home to Alabama the SES light came on so we returned to his shop. Fuel trims were high (-14), so they cut back the injector flow rate table to correct this problem, and went the other way on the PE table so as to not change WOT fuel. Well, fuel trims are still runnning around -14, but not for long!!
    A lot of people consider changing the IFR table an old school way of tuning and ironically most people that do it are using LS1Edit. The guy that tuned mine originally did it and he used LS1Edit. All this is doing is tricking the PCM into thinking that you have larger or smaller injectors than you actually do. The PCM adjust flow by increasing or decreasing pulse width. If you tell the PCM that there are smaller injectors than there actually are, it will send a pulse width based on calculations made with the smaller injectors. Since the injectors are bigger than the PCM thinks they are, you get more fuel, which in turn richens up the AFR.

  15. #15
    Being SC, I would look into a SD tune. The 1 bar SD upgrade works great. The MAF can be tricky at times.

  16. #16
    Senior Tuner Russ K's Avatar
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    A 1 bar SD will be of no use since vetteman3 is boosted. A Maf tune is the best way to tune a low boost ~7lbs or less application.

    Russ Kemp

  17. #17
    Quote Originally Posted by Russ K
    The 2001 & up PCM only has a primary VE table. Leave the VE table stock and tune the Maf table. Find one of my Maf config files, the STFT & LTFT histograms will then help tune the Maf. You really need to get a wideband to tune your car.

    Russ Kemp
    not to change the topic, but where could I find one of your MAF config files?

    I have a 2001 Z06 and I want to plot MAF vs LTFT and MAF vs STFT but I am not sure how to set up a config file in HPtuners.

    by the way +1 for the MAF tuning, my VE table is stock and my MAF table is tweaked and the car drives great. I would just like to get the MAF more in line
    01 Z06...modified

  18. #18
    Senior Tuner 5_Liter_Eater's Avatar
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    Import these histograms.
    Attached Files Attached Files
    Bill Winters

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    "When life hands you lemons you upgrade to a C6." - Me

    Always post a tune and a log when asking questions.

  19. #19
    thanks!
    01 Z06...modified