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AFR advice needed for ethanol/gasoline mix

Discussion in 'EFI Tuning Questions and Engine Management' started by silver82GT, May 8, 2020.

  1. silver82GT

    Joined:
    Sep 20, 2005
    I need some advice on what AFR to set my FiTech for. Currently I run pump E10 94 octane fuel, E85 isn't available here. I bought some E98 to blend with the E10 to get either E20 or E30. Currently I run 14.0 at cruise and idle and 11.5 under boost. What would the correct AFR be for boost with E20 and E30? Is there a formula to use to figure it out?
     
    silver82GT, May 8, 2020
    #1

  2. TTF/Ken Staff Member

    Joined:
    Dec 31, 2011
    Switch your wideband to display lambda and go by that, it will give you the correct AFR no matter the fuel type. 1=stoichometric, anything above 1 is leaner, anything below 1 is richer. Under boost, keep lambda .8 or lower (richer) depending on the engine, amount of boost, etc.
     
    TTF/Ken, May 9, 2020
    #2

  3. Briansshop

    Joined:
    Dec 12, 2006
    I run E10 93 in mine. Idle 13.5,cruise 14. Above 8psi I run W/M, and target 11.5,up to 20psi boost. Have ran 12/1 at 20psi and was getting into some detonation on long,1/4 mile,pulls.
     
    Briansshop, May 9, 2020
    #3

  4. B E N

    Joined:
    Nov 22, 2016
    Stoic values:
    e10: 14.12
    e20:13.54
    e30 12.96

    As you can see it's important to know the actual ethanol content, you should be checking it if your going to the trouble of mixing your own.

    Most tuning is done in Lambda, I don't think that jives with fitech so here is the conversion: Under boost you want to be at .75-.8 lambda. For e20 at .75 you want 13.54*.75=10.155 afr
     
    B E N, May 9, 2020
    #4

  5. silver82GT

    Joined:
    Sep 20, 2005
    Thank you very much, this was exactly the info I needed. Apparently I have been running a little lean even with E10. I will be mixing my own fuel so that won't be a problem.
     
    silver82GT, May 9, 2020
    #5

  6. ashford

    Joined:
    Nov 24, 2008

    keep in mind the afr values displayed are a conversion of lambda to gas scale unless the display is set up for something else. it will not be actual afr value for a fuel other than straight gas.

    if you are showing 14.7 on a wideband that is in gas scale and have something else in the tank your actual afr is the stoich value for that fuel.

    ie if your widebans shows 14.7 and it has e30 in it, actual afr is 12.96.
     
    ashford, May 9, 2020
    #6
    underpsi68 likes this.

  7. underpsi68

    Joined:
    Jul 9, 2005
    On gasoline display I run e85 at 14.0 at idle, 14.7 cruise, and 11 at 15lbs, 9:1 compression, aluminum heads.
     
    underpsi68, May 9, 2020
    #7

  8. silver82GT

    Joined:
    Sep 20, 2005
    So if I understand correctly I don't need to change the AFR settings in the FiTech, I just leave them as is and the computer will do the rest. This would be why FiTech says to increase the displacement value in the settings to increase the amount of fuel injected.
     
    silver82GT, May 9, 2020
    #8

  9. silver82GT

    Joined:
    Sep 20, 2005
    I will leave my settings alone then and just add fuel.
     
    silver82GT, May 9, 2020
    #9

  10. Mnlx

    Joined:
    Sep 20, 2009
    I don't think i've ever seen anyone change their wide band for fuel choice, they either use lambda, or just tune with the gas scale.
     
    Mnlx, May 9, 2020
    #10
    underpsi68 likes this.
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