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Thread: Flex Fuel - Master Enable/Disable

  1. #41
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    In my scan I did notice some flex fuel options for my 2008 TBSS.
    Thanks,
    Mr. 2008 SS
    Last edited by Mr. 2008 SS; 04-05-2011 at 07:57 PM.

  2. #42
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    Quote Originally Posted by DSteck View Post
    have I told you lately... That I love you?
    x2!

  3. #43
    Senior Tuner DSteck's Avatar
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    Any updates? I am trying to set up a buddy's 441 LS7 with flex fuel without buying Brand X.

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  4. #44
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    I am running E-85 in my TBSS 08
    1. change stoich
    2.Put some timing in
    3.I tried the Flex fuel enable and well a DTC light lean turned off no problem
    4. Look and logs at my tune any input would be good

    Thanks,
    Mr. 2008 SS

  5. #45
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    Quote Originally Posted by Mr. 2008 SS View Post
    I am running E-85 in my TBSS 08
    1. change stoich
    2.Put some timing in
    3.I tried the Flex fuel enable and well a DTC light lean turned off no problem
    4. Look and logs at my tune any input would be good

    Thanks,
    Mr. 2008 SS
    i think when you enable the FF setting, you leave the stioch table alone, and the vehicle respons to the swing in LTFT + STFT's and adjusts stioch to put the values at 0.

    so your running 93 with 0 ethanol. fuel trims are 0, now you fill with E85, and fuel trims spike to +51%. ecm varies stioch, and everything falls back in line with 0 fuel trims, and proper spartk. maybe the alchohol spark table and multi are used now. who knows?

    -Carl

  6. #46
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    Ok, I will try both but the stoich is the key right?
    1.Turn on the FF setting and leave stoich alone
    2. Change stoich and keep FF off

    Right ???

    Thanks,
    Mr. 2008 SS

  7. #47
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    yep, you stioch table is populated with the correct values from stock right? 0% = 14.68 and 10% = 14.13 and 85% = 9.765

    something along those lines would be correct. also make sure you stft's or ltft are consistance throught the entire maf or ve table, and not swinging on both sides of 0

    this is something i would try in my driveway, not at the pump. lol

  8. #48
    I'm assuming this didn't work on your TBSS?

  9. #49
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    How would you "change stoich"? If it's a 0-1V oxygen sensor, stoich is stoich, for any fuel. It just measure the amount of oxygen left. You just have to put in less fuel for it to read stoich with a higher AFR. Maybe I'm on another page. When you first change fuels, it will take a few minutes for it to change the injection times back right to where it's reading stoich again.

  10. #50
    They're talking about this table:

    Stoich AFR Table: This table is used for vehicles with the dual fuel option (alcohol)
    The base stoichiometric fuel/air rate is determined by a returned value from this table. The position on the table is determined by the amount of alcohol in the fuel system as reported by the vehicles fuel composition sensor. The rate ranges from 0% to 100% alcohol.




    Quote Originally Posted by TheGrinch View Post
    How would you "change stoich"? If it's a 0-1V oxygen sensor, stoich is stoich, for any fuel. It just measure the amount of oxygen left. You just have to put in less fuel for it to read stoich with a higher AFR. Maybe I'm on another page. When you first change fuels, it will take a few minutes for it to change the injection times back right to where it's reading stoich again.

  11. #51
    The stoich AFR isn't the same for E85 vs. gasoline. Therefore your commanded AFR has to change, or your fuel trims and what not will be WAY out of wack and line, and you'll eventually throw a rich or lean code depending on what fuel you're switching to/from. The idea of the physical or virtual sensor is to determine the alcohol content, and there for the stoich AFR of your fuel mixture, then command the correct stoich AFR for your fuel. I don't think you mean stoich is stoich, lamda is lamda, but stoich AFR isn't the same for all fuels.

  12. #52
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    I think I see what you're saying with commanded AFR, Seems you'd really just changing the injection times for the different fuel.

    I've been tuning a CNG bi-fuel truck, which is a vastly different AFR, but nothing changes with the closed loop system. I have different injectors though, they follow the same injection signal, and I just change the injection times until fuel trims are dialed in for both fuels, then it uses the exact same O2's as the normal petrol system. When it's stoich, the fuel trims are the same.

  13. #53
    Quote Originally Posted by TheGrinch View Post
    I think I see what you're saying with commanded AFR, Seems you'd really just changing the injection times for the different fuel.

    I've been tuning a CNG bi-fuel truck, which is a vastly different AFR, but nothing changes with the closed loop system. I have different injectors though, they follow the same injection signal, and I just change the injection times until fuel trims are dialed in for both fuels, then it uses the exact same O2's as the normal petrol system. When it's stoich, the fuel trims are the same.

    Yeah, but think about this, if you don't' change the command AFR from gasoline to E85, you're going to be MISSINg 33% of the fuel the system needs to get to stoich, and your fuel trims are going to be like +33% or more. Your o2 sensors are working, and your car is trying to get to stoich/lamda, but it needs a good starting point, and that's the target AFR. I am sure modifying target AFR changes how much fuel is injected, that's as designed.

  14. #54
    Senior Tuner DSteck's Avatar
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    Ohhhhhhhhhh Chris........................


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  15. #55
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    shhhh dont make them mad. oke:
    Last edited by carlrx7; 02-12-2012 at 02:43 PM.

  16. #56
    Senior Tuner LSxpwrdZ's Avatar
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    Hmm...
    James Short - [email protected]
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    2020 Camaro 2SS | BTR 230 | GPI CNC Heads | MSD Intake | Rotofab | 2" LT's | Flex Fuel | 638rwhp / 540rwtq
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  17. #57
    Any update on this?

    I'd love to be able to switch back and forth from 93 and E-85.

  18. #58
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    Ditto, it sounds like Brand X can do this?
    2012 Chevy Cruze A6 1LT RS

    Formerly - 2004 GTO, 2002 Z28, 2007 Colorado, 2008 Silverado

  19. #59
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    Looks like with Brand X you have to modify your ECM harness. No thanks!
    2012 Chevy Cruze A6 1LT RS

    Formerly - 2004 GTO, 2002 Z28, 2007 Colorado, 2008 Silverado

  20. #60
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    it can do it but its not as simple as enabling it ... the original OS needs to support it ( or at least be butchered/segmented together from one that does support it)... the switch in HP's is purely there to disable it in an OS that supports it at the moment
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