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Thread: E85 vs E10 part throttle tuning

  1. #1
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    E85 vs E10 rich/lean

    Hi, ive got a stock LS3, with Whipple. Added Flex Fuel sensor, DSX aux pump and 100lb ID1050X injectors. Got car running perfectly on E10 then added enough E85 to get to E65. Car started up idling lean. LTFTs quickly maxed out at 30+% with some STFT positive 7-8% as well to hold stoich. It was tending rich under brief WOTs. Ok, long story short, so I logged STFT+LTFT did allot of cruise from start, all part thottle and used this data to richened up down low by adding to the MAF vs freq curve at the low end. I gradually did some WOT capture via WB to learn it was very rich at WOT so eventually dialed the high load regions in via subtracting for eqratio error from MAF vs Freq up high.

    Car ran perfect with this updated MAF curve.

    Fast forward to today, I went the other way and filled up with enough E10 to end up at about E17 according to my test kit, the FF sensor shows about 17.5.

    As soon as I started the car it did not want to idle, and died. Tried three or four times and it died each time. I was able to keep it running with added throttle long enuf for the WB to get done heating and show 0.75lambda, so I?m sure shes pig rich. Probably the effect of my previous tuning MAF for the lean E65 condition. I had my laptop with me so I flashed back the original E10 tune I had in the car before starting with the E65 MAF calibration. Car started, ran and I got home.

    So, I am wondering, is there a table or tables I should be editing to calibrate how the ecu adjusts the part throttle AFR by factoring in the fuel?s stoich from the FF sensor? I understand which tables do this under PE, but not part throttle. Tuning MAF for the AFR conditions seems to lead to different airflows needed delending on E%. I dont want to develop separate Exxx tunes and needing to flash when I change fuels...but it seems thats about what I have now. I guess i could flash a MAF vs Freq that is an average between my E10 and E65 MAF calibrations and it would probably idle.

    How is it best done?

    Thank u so much in advance, for all advice!

    P.S One thing that bothers me, how could the car start so poorly right after adding 17gals of E10 on top of the couple gals of E65? I mean the FF sensor cannot have received any of the new fuel at the lower E concentration, it is not a return fuel setup, so only after fuel is consumed at the rails can fuel flow up to the FF sensor to be sensed, I mean thats what transition volume and delay volume is about, right? ...obviously Im confused, lol. I apologize for being ignorant.
    Last edited by ngc1068; 2 Weeks Ago at 05:45 PM.
    2016 Chevy SS M6 LS3, Whipple 2.9, 4.000 pulley, Doug Thorley Tri-Y LTs, DSX Aux Fuel Pump, Flex Fuel Sensor, 100lb ID1050X?s, Monster LT1-S tripple-disk clutch.

  2. #2
    Senior Tuner
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    tune file ?

  3. #3
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    Quote Originally Posted by 07GTS View Post
    tune file ?
    Realized the original file I was running closer to E20, not E10.

    Here are two files, E20 and E65, the only difference is the MAF vs Freq.

    E65 v1.hpt

    E20 v1.hpt
    2016 Chevy SS M6 LS3, Whipple 2.9, 4.000 pulley, Doug Thorley Tri-Y LTs, DSX Aux Fuel Pump, Flex Fuel Sensor, 100lb ID1050X?s, Monster LT1-S tripple-disk clutch.

  4. #4
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    [ecm 12303]if u havnt changed it try halving it, [ecm 13338] make all zero, [ecm 12442] make all 1.0, change ethanol delay volume to 0.18L and comp change thresh to 2%, may have to adjust some fueling after changes then see if it helps at all