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Thread: Quick guide to simultaneous VVE/MAF calibration for gen4+

  1. #41
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    Quote Originally Posted by LSxpwrdZ View Post
    Definitely not mixing definitions around. You only see all those models when you have it in blended mode... Obviously filtering transients which should be done anytime you are trying to dial in a fuel model anyhow. Hence why I also said using it in MAF only mode. Dyno tuning everyday with an eddy brake dyno proves this functional 100%. One WOT pull both MAF and VE/VVE are within 1-2% error.
    The airflow measurement is MAF only in blended mode as long as there are no transients. That's why this method works and why there is no need to waste time switching between them. If you're dubious, you can plot MAF, dynamic airflow and volumetric efficiency airflow in the scanner. At steady state, MAF and dynamic airflow are always right on top of each other even when GMVE is not disabled. And even if the GMVE is completely wrong. So long as you keep steady, airflow calculation from speed density is not used to determine fuel mass at all. It is however used to update the VE correction factor.

    The patent is here with some block diagrams if you want to read about it: https://patents.google.com/patent/US20050060084A1/en

    I know this is accurate because I designed software for GM and have seen all of the source code for this software

  2. #42
    Senior Tuner LSxpwrdZ's Avatar
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    That all confirms what I am saying. I'm only forcing prediction dynamics and GMVE disabled so that any/all airflow calcs are forced to come from MAF derived airflow. The dynamic airflow in the scanner will report that.

    Besides the point, using the method I described works because you can simply force GMVE only mode after calibrated with my method and will see the same lambda error that would be seen by my GMVE Error calc.
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  3. #43
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    Yeah that's the conventional method. I think that was just how the writeups were done years ago when people first got into the gen 4 stuff. Odd to call it dynamic airflow when your intention is to collect MAF only, but I digress. This method just allows you to combine the procedures and save time and potentially driveability issues while doing all this. Any method you use must be filtered for steady state data - so its MAF only regardless. Just a recommendation, you don't have to do this way

  4. #44
    Advanced Tuner ttz06vette's Avatar
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    Quote Originally Posted by smokeshow View Post
    Yeah that's the conventional method. I think that was just how the writeups were done years ago when people first got into the gen 4 stuff. Odd to call it dynamic airflow when your intention is to collect MAF only, but I digress. This method just allows you to combine the procedures and save time and potentially driveability issues while doing all this. Any method you use must be filtered for steady state data - so its MAF only regardless. Just a recommendation, you don't have to do this way
    Your method worked like a charm for me. Car has never ran better. My steady state is dialed in.

  5. #45
    Quote Originally Posted by ttz06vette View Post
    Your method worked like a charm for me. Car has never ran better. My steady state is dialed in.
    You have Volumetric Efficiency (mg?K/kPa) PID in your channels and it gives you an actual number? Mine is only reading zero as well as my chart only reads zero. I contacted HPT on the suggestion of Smokeshow and they responded with a link how to use VCM scanner. So they were zero help.

  6. #46
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    Quote Originally Posted by benf View Post
    You have Volumetric Efficiency (mg?K/kPa) PID in your channels and it gives you an actual number? Mine is only reading zero as well as my chart only reads zero. I contacted HPT on the suggestion of Smokeshow and they responded with a link how to use VCM scanner. So they were zero help.
    I rarely see it 0 constantly for vehicles with the VVE...only a couple times I believe. If they've got the CAN definition wrong, it's out of your hands.

    There is a way to generate GMVE in the scanner based on other parameters. It'll give you the full GMVE value instead of an error percentage...but you can calculate the error in excel if you need.

  7. #47
    i heard back from HPT and i had to send them a bunch of files and hopefully i will hear back from them Monday or Tuesday with good news. I know it isnt just me as another member with a 2020zl1 gets all zeros too. Like you said, if they dont have that pid correct for my car i wont ever get it to work right

  8. #48
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    Quote Originally Posted by smokeshow View Post
    There is a way to generate GMVE in the scanner based on other parameters
    1 way to calculate GMVE.

    Here is how I did it a while back. Without MAT I found the bias of 0.35 worked for me. The bias also changes depending on how your driving. E.g, for power pulls, your bias could start out at 0.35 but by the end of the pull be down at 0.31. Spent way to many hours on this. Trust me here, best is with MAT.

    You need 2 formulas. One for closed loop, and another for open loop where your commanded AFR is used.

    This formula sitting inside smokeshows formula ends up been pretty nasty to look at. Especially worse if you make an error, then trying to work out where you mucked up

    Without MAT
    GMVE = IFR * IPW * AFR * (IAT + (ECT - IAT) * BIAS) / MAP

    With MAT
    GMVE = IFR * IPW * AFR * MAT / MAP

    IFR g/sec Injector flow rate
    IPW msec Injector pulse width
    MAT degK Manifold air temperature
    IAT degK Intake air temperature
    ECT degK Engine coolant temperature
    MAP kPa Manifold air pressure
    BIAS Constant, 0.2875 -> 0.35

    Required channels:
    Manifold Air Temp
    Engine Coolant Temp (if no manifold air temp available)
    Intake Air Temp (if no manifold air temp available)
    Intake Manifold Absolute Pressure
    Injector Pulse Width Avg.
    Injector Flow Rate

    Credit to: http://redhardsupra.blogspot.com/200...odels.html?m=1

  9. #49
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    Hah that's funny, Marcin and I go back and forth all the time about this stuff.

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    That's awesome man, both you guys are seriously switched on!!! And that blog is from 2008!

    For the others following who don't have GMVE here is a screenshot showing how it works with Marcin and smokeshows formulas compared against each other. Both agree bar +/- a few % here and there, nothing to split hairs on. Remember this is for steady state driving only!

    The approaches to how you use your histogram are different. Smokeshows is the classic right click multiply by percent where as Marcins is a straight copy and paste.

    The 2 approaches seem similar but they are completely different.
    smokeshow is using what the ECM thinks the VVE is and displaying how far out that number is in % based on steady state MAF and fuel trim data
    Marcin is telling you what the GMVE actually is

    Each to there own, I like smokeshows because in % its easy at a quick glance when driving to see how your are tracking tune to tune. Marcins isn't immediately obvious until you are back in the tune modifying the VVE.

    1.PNG

  11. #51
    Advanced Tuner HawkZ28's Avatar
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    I've had 1 scan session with my 6.2L Sierra changing VVE only, and it made a noticeable difference in drivability/feel. Appreciate you starting this thread and sharing!

    2 questions- should I focus on one or the other- MAF and then VVE, wash rinse and repeat, or do both MAF and VVE at the same time?

    Also, this is my filter. Care to critique?

    [50090.156.slope(2000)]<2 AND [50090.156.slope(-2000)]<2 AND [50030.91]>37
    Hawk

  12. #52
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    Forgive my ignorance it has been a decade since I last plugged my scanner in. I have a ctsv that is pretty rich so I have configured the maths as stated in the first post and I'm successfully plotting data. I assume this % errors and i would apply this to the vve table? also I can't remember how to function filter the histo for max and min values.
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  13. #53
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    Quote Originally Posted by HawkZ28 View Post
    I've had 1 scan session with my 6.2L Sierra changing VVE only, and it made a noticeable difference in drivability/feel. Appreciate you starting this thread and sharing!

    2 questions- should I focus on one or the other- MAF and then VVE, wash rinse and repeat, or do both MAF and VVE at the same time?

    Also, this is my filter. Care to critique?

    [50090.156.slope(2000)]<2 AND [50090.156.slope(-2000)]<2 AND [50030.91]>37

    I don't think you need to go a full +/- 2 seconds, maybe +/- 350 ms would be sufficient. Also does your engine idle lower than 37 kpa?
    You may want to add in ECT and IVT filters as well to be sure you are up to operating temp, and injector tip temp for the "rich after flash" and/or heat soak conditions. Do MAF and VVE at the same time, that is the idea of this thread.
    Last edited by NotSure; 03-03-2021 at 03:11 PM.

  14. #54
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    Quote Originally Posted by robbyredneck View Post
    Forgive my ignorance it has been a decade since I last plugged my scanner in. I have a ctsv that is pretty rich so I have configured the maths as stated in the first post and I'm successfully plotting data. I assume this % errors and i would apply this to the vve table? also I can't remember how to function filter the histo for max and min values.
    Top of the Graph section, the + and - signs are for max and min. A=average. C=# of counts

  15. #55
    Advanced Tuner robbyredneck's Avatar
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    Thanks but I meant setting limits for filtering out erroneous data . I think i remember now
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  16. #56
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    In case anyone is still fighting the GMVE pid showing 0 constantly, they updated it in the last beta and it actually works now. I'll be giving it a go with it plugged into the maths tomorrow. It was so much easier to set up the math with this PID lol

  17. #57
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    Quote Originally Posted by robbyredneck View Post
    Thanks but I meant setting limits for filtering out erroneous data . I think i remember now
    Filters have been probably the biggest issue/source of questions following this post. Its definitely a different topic entirely though, as it depends on what you have available to monitor, what vehicle/make it is and what you're even trying to filter for. The scanner leaves a bit to be desired as well in terms of available filters because it does not allow for things like ignoring fuel trim data for a predetermined amount of time following a transient event. You can filter everything perfectly for the transient events themselves but it still assumes there are no other dynamics at play...for example port wall rewetting after a DFCO disable or the delay time for the exhaust gases reaching the O2 sensors. A steady-state delay timer filter would be optimal here, which HPT cannot do yet.

    A writeup for proper data filtering is on my endless to-do list lol.

  18. #58
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    Part 2 coming soon...

  19. #59
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    Quote Originally Posted by smokeshow View Post
    Part 2 coming soon...
    If you have time smokeshow, could you give these a try and tweak them with some of your tricks...

    Change the <2 term to change the aggressiveness of the filter on throttle changes

    Code:
    Closed Loop
    
    ITT < 60degC AND Ignore a shift / torque management event for 0.5s either side AND Steady state throttle AND Fuel Trim Cell in closed loop run
    
    [6215.241]<60 AND [2517.161.avg(500)]=0 AND [2517.161.avg(-500)]=0 AND (abs([50090.156.slope(1500)])+abs([50090.156.slope(-500)]))<2 AND ([6310]=7 OR [6310]=9 OR [6310]=14 OR [6310]=15)=0
    Code:
    Open Loop
    
    ITT < 60degC AND Ignore a shift / torque management event for 0.5s either side AND Steady state throttle AND Fuel Trim Cell in power enrichment 1s after entering PE and 1s before leaving PE
    
    [6215.241]<60 AND [2517.161.avg(500)]=0 AND [2517.161.avg(-500)]=0 AND (abs([50090.156.slope(1500)])+abs([50090.156.slope(-500)]))<2 AND [6310.avg(1000)]=9

  20. #60
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    Quote Originally Posted by smokeshow View Post
    Part 2 coming soon...
    Excellent! Excited about continuing to improve what you have already helped us with. Thanks.