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Thread: Why are most professional "tuners" doing Flex Fuel timing wrong?

  1. #61
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    Quote Originally Posted by J2Motorsports View Post
    Fixing a tune now from a "big shop". Car came in on e85, no sensor at all, stoich afr table still stock. Car didn't even know it was running on e85.

    Wow!! Just wow.
    2017 Silverado LTZ

  2. #62
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    Good read guys, I actually read the entire post on the V forum, I'm not the best by any means...I'm not well known at all, but I've had to fix many tunes because of the whole "I had my car tuned by this guy because he is well known, has a big shop and is awesome, and tuned my car in an hour"...

    ME: oh is he...well how come it takes 2 or 3 tries in the morning to keep it running?
    Customer: because race car and big cam/TB...
    ME: oh ok, looks at tune, licenses it, fixes it. Only ask for money for the credits.

  3. #63
    Great info here, thanks for all the awesome info

  4. #64
    Maybe i missed it in this thread but i would think this would be the easiest way to do it. Past special add and subtract between main timing map and flex add.

    Main timing example.
    main timing.jpg

    Shitty looking flex adder table
    flex adder.jpg


    Add them together to get total flex timing, make changes then subtract main timing map back out.
    total flex timing.jpg

  5. #65
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    That's how you do it - just make sure to "hand" add in the EQ table if you choose to use it, which I recommend doing Had one recently that had an ethanol sensor shorting out and it was throwing all of the ethanol timing in with 93 octane fuel - so keep things like that in mind when tuning...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  6. #66
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    ALCOHOL ADDER / MBT TIMING TABLES ECM #12661 - I think I finally figured out what these tables do or rather somewhat what they control... I know it was discussed a while back that these tables have nothing to do with mbt timing limitations and that they were in fact solely for transient fueling calculations, but here's what I found... Car was a 2012 SS Camaro - manual transmission "important part to remember here", whipple (10psi), cam, open exhaust, boost reference return fuel system setup to run on 93 and E85 via it's alcohol sensor... Tuned in on 93 no problem - drained the tank like always after doing my last 93 tune verification pull and filled it with E85 (82ish percent pure)... Well unbeknown to me - it split the boost regulator reference lines - thankfully on it's last 93 pull... Well, for the E85 I also had transients and idle corrections overly aggressive - this combined with the now overly rich fuel mixture from the lack of vacuum reference going to the regulator combined with the vacuum leak on top of everything had my E85 starts starting normally then going super rich causing the engine rpms to drastically drop and then for whatever reason I was suddenly running negative ignition timing with the engine barely churning over at 100ish rpms... I thought it was the torque model - went back to stock = no change - if anything maybe worse / transients back to stock = better - would at least idle, but seriously lacking and weak / idle back to stock and really detuned throttle ramps = better would idle without rpms jumping all around, but still would pull timing into the negatives just when I went to let the clutch out and go super rich because of it (combined with the fuel pressure regulator issue of course)

    Well, I figured fueling just didn't go super rich because of the E85 stoic settings - maybe it was a weird made E85 from some "off" station somewhere as I do know Mom and Pop stations don't have to abide by the same rules as the big name nation wide stations do, but this was unlikely to cause this - so started looking around and found the 3 different rubber couplings that were either split or fixing to fall off - figured, well this is my problem and only problem - right? Fixed the problem - fires up, idles great - think all is well in the world again, go to let the clutch out "no gas assist" and here we are back to rich and negative ignition timing, so at this point I'm scratching my head - rpm's are dropping yet it's pulling timing - wtf? Then it dawned on me - the E85 alcohol adder MBT table that no one knows what it does that because of this thread I started populating with values from a stock E85 tune........ Started thinking about things that I've noticed even on gas vehicles with manual transmissions.......

    As we all know or at least "think" we all know - the main timing table limits the amount of timing that "should" be allowed to be added in during idle torque "reserve" request limited again by the spark error tables - correct - ever notice on rare near stall or stall conditions where timing jumps way above this?

    As best I can tell - during "near" stall conditions the timing MBT tables are added to the current idle timing or at least most definitely the alcohol adder MBT table is added in during these conditions - it's not just for transients as it was thought... By modifying this table and this table alone, I was able to calm down my E85 issues...

    So, VERY long story short - if your having weird E85 problems where it's pulling timing for some unknown reason and your not sure where it's coming from with this table populated - look into it - might solve your issues...

    Hopefully this might help someone...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  7. #67
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    Quote Originally Posted by GHuggins View Post
    ALCOHOL ADDER / MBT TIMING TABLES ECM #12661 - I think I finally figured out what these tables do or rather somewhat what they control... I know it was discussed a while back that these tables have nothing to do with mbt timing limitations and that they were in fact solely for transient fueling calculations, but here's what I found... Car was a 2012 SS Camaro - manual transmission "important part to remember here", whipple (10psi), cam, open exhaust, boost reference return fuel system setup to run on 93 and E85 via it's alcohol sensor... Tuned in on 93 no problem - drained the tank like always after doing my last 93 tune verification pull and filled it with E85 (82ish percent pure)... Well unbeknown to me - it split the boost regulator reference lines - thankfully on it's last 93 pull... Well, for the E85 I also had transients and idle corrections overly aggressive - this combined with the now overly rich fuel mixture from the lack of vacuum reference going to the regulator combined with the vacuum leak on top of everything had my E85 starts starting normally then going super rich causing the engine rpms to drastically drop and then for whatever reason I was suddenly running negative ignition timing with the engine barely churning over at 100ish rpms... I thought it was the torque model - went back to stock = no change - if anything maybe worse / transients back to stock = better - would at least idle, but seriously lacking and weak / idle back to stock and really detuned throttle ramps = better would idle without rpms jumping all around, but still would pull timing into the negatives just when I went to let the clutch out and go super rich because of it (combined with the fuel pressure regulator issue of course)

    Well, I figured fueling just didn't go super rich because of the E85 stoic settings - maybe it was a weird made E85 from some "off" station somewhere as I do know Mom and Pop stations don't have to abide by the same rules as the big name nation wide stations do, but this was unlikely to cause this - so started looking around and found the 3 different rubber couplings that were either split or fixing to fall off - figured, well this is my problem and only problem - right? Fixed the problem - fires up, idles great - think all is well in the world again, go to let the clutch out "no gas assist" and here we are back to rich and negative ignition timing, so at this point I'm scratching my head - rpm's are dropping yet it's pulling timing - wtf? Then it dawned on me - the E85 alcohol adder MBT table that no one knows what it does that because of this thread I started populating with values from a stock E85 tune........ Started thinking about things that I've noticed even on gas vehicles with manual transmissions.......

    As we all know or at least "think" we all know - the main timing table limits the amount of timing that "should" be allowed to be added in during idle torque "reserve" request limited again by the spark error tables - correct - ever notice on rare near stall or stall conditions where timing jumps way above this?

    As best I can tell - during "near" stall conditions the timing MBT tables are added to the current idle timing or at least most definitely the alcohol adder MBT table is added in during these conditions - it's not just for transients as it was thought... By modifying this table and this table alone, I was able to calm down my E85 issues...

    So, VERY long story short - if your having weird E85 problems where it's pulling timing for some unknown reason and your not sure where it's coming from with this table populated - look into it - might solve your issues...

    Hopefully this might help someone...
    Great info as always. Thanks for sharing.

  8. #68
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    Quote Originally Posted by GHuggins View Post
    ALCOHOL ADDER / MBT TIMING TABLES ECM #12661 - I think I finally figured out what these tables do or rather somewhat what they control... I know it was discussed a while back that these tables have nothing to do with mbt timing limitations and that they were in fact solely for transient fueling calculations, but here's what I found... Car was a 2012 SS Camaro - manual transmission "important part to remember here", whipple (10psi), cam, open exhaust, boost reference return fuel system setup to run on 93 and E85 via it's alcohol sensor... Tuned in on 93 no problem - drained the tank like always after doing my last 93 tune verification pull and filled it with E85 (82ish percent pure)... Well unbeknown to me - it split the boost regulator reference lines - thankfully on it's last 93 pull... Well, for the E85 I also had transients and idle corrections overly aggressive - this combined with the now overly rich fuel mixture from the lack of vacuum reference going to the regulator combined with the vacuum leak on top of everything had my E85 starts starting normally then going super rich causing the engine rpms to drastically drop and then for whatever reason I was suddenly running negative ignition timing with the engine barely churning over at 100ish rpms... I thought it was the torque model - went back to stock = no change - if anything maybe worse / transients back to stock = better - would at least idle, but seriously lacking and weak / idle back to stock and really detuned throttle ramps = better would idle without rpms jumping all around, but still would pull timing into the negatives just when I went to let the clutch out and go super rich because of it (combined with the fuel pressure regulator issue of course)

    Well, I figured fueling just didn't go super rich because of the E85 stoic settings - maybe it was a weird made E85 from some "off" station somewhere as I do know Mom and Pop stations don't have to abide by the same rules as the big name nation wide stations do, but this was unlikely to cause this - so started looking around and found the 3 different rubber couplings that were either split or fixing to fall off - figured, well this is my problem and only problem - right? Fixed the problem - fires up, idles great - think all is well in the world again, go to let the clutch out "no gas assist" and here we are back to rich and negative ignition timing, so at this point I'm scratching my head - rpm's are dropping yet it's pulling timing - wtf? Then it dawned on me - the E85 alcohol adder MBT table that no one knows what it does that because of this thread I started populating with values from a stock E85 tune........ Started thinking about things that I've noticed even on gas vehicles with manual transmissions.......

    As we all know or at least "think" we all know - the main timing table limits the amount of timing that "should" be allowed to be added in during idle torque "reserve" request limited again by the spark error tables - correct - ever notice on rare near stall or stall conditions where timing jumps way above this?

    As best I can tell - during "near" stall conditions the timing MBT tables are added to the current idle timing or at least most definitely the alcohol adder MBT table is added in during these conditions - it's not just for transients as it was thought... By modifying this table and this table alone, I was able to calm down my E85 issues...

    So, VERY long story short - if your having weird E85 problems where it's pulling timing for some unknown reason and your not sure where it's coming from with this table populated - look into it - might solve your issues...

    Hopefully this might help someone...
    on the 750 car we have discussed numerous times about. it was having really weird hard starts when hot or cold actually. So in "theory" it would be a driver of timing and fueling in one shot? Negative timing would tank the timing and dump fuel?
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  9. #69
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    That's what I was seeing - negative timing and then a fuel dump - mine was originally idling on 6 or so degrees with the startup flare timing correction coming into the picture then the negative alcohol adder table was bringing it down into the -2 to -3 range if it would have it's startup stumble or even after having that fixed, I would go to pop the clutch out - as I like to tune your usual worst case fire and go scenario
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  10. #70
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    Quote Originally Posted by GHuggins View Post
    That's what I was seeing - negative timing and then a fuel dump - mine was originally idling on 6 or so degrees with the startup flare timing correction coming into the picture then the negative alcohol adder table was bringing it down into the -2 to -3 range if it would have it's startup stumble or even after having that fixed, I would go to pop the clutch out - as I like to tune your usual worst case fire and go scenario
    i see! the whole fire and go thing didn't work well for this car in particular lol more fire than go.

    This actually gives me a whole new plan of attack on flex fuel cars. I knew the "MBT" tables were not really the max end all timing tables, just wasn't fully aware of their adverse affects on everything else.
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  11. #71
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    Yeah, I actually wound up putting in +2 / any more timing addition than this and it would stall immediately on E85 / less - well it had more torque as E85 likes negative timing around idle vs the pump gas timing it runs on, but (-) timing seemed to cause other adverse affects that didn't work out well with this cam/blower combo... I actually had to tune this one completely different on E85 than I normally do, but opened my eyes to quite a few things - I'm even doing the main E85 timing tables differently - once again - because of this one car and what I was experiencing with normal driving and everything else going on... Wish someone had taut me all of this years ago, but that's what tuning is all about right - think you know enough, then here comes the curb ball to put you back in your place
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  12. #72
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    Quote Originally Posted by GHuggins View Post
    That's how you do it - just make sure to "hand" add in the EQ table if you choose to use it, which I recommend doing Had one recently that had an ethanol sensor shorting out and it was throwing all of the ethanol timing in with 93 octane fuel - so keep things like that in mind when tuning...

  13. #73
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    You talkin' 'bout me?

  14. #74
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    Maybe? Yours is doing dang good now that your getting the bugs out though isn't it

    Actually yours is just another reason I've changed how I do things - you might notice some slight changes when you get that turbo back on and I send you an update
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  15. #75
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    This has actually made me redirect an upcoming retune on a v as it does similar stupid things on start up.
    The most hated, make the most power.
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  16. #76
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    I wonder if there is a missing multiplier table or something? Some vehicles/calibrations don't seem to be affected as much as others. Totally makes sense though with some of the strange startup scenarios.
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  17. #77
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    There is one missing "time" table that I'm trying to get HPT's to add - hopefully will be added in with the 200ish other tables being added in for the GM side of things... It's a time to transfer from cranking spark to running spark though - not sure how it would play into this?
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  18. #78
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    Quote Originally Posted by GHuggins View Post
    Maybe? Yours is doing dang good now that your getting the bugs out though isn't it

    Actually yours is just another reason I've changed how I do things - you might notice some slight changes when you get that turbo back on and I send you an update
    Mine is doing exceptionally well after all of the gremlins have been fixed. Hoping to get the turbo back tomorrow or Thursday. Will start building a shrine to Greg Huggins and Passion Performance soon after.

    Thanks for the great contributions to the forum and to me personally. Much appreciated.

  19. #79
    So should I populate [ECM] 12678 Flex Fuel Spark or not?

    Anyone have a base tune file with it that I can copy to have a starting point?

    I have a 2010 SS L99.

    Thanks...
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  20. #80
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    Don't know if anyone knows for sure, but leaving the flex fuel spark adder table zeroes or negative 2s should work to the point of not causing other problems.
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC