Flex Fuel Tune VS Straight E85 tune

Discussion in 'V8 5.0L Engine / Mods: Bolt-ons, Exhaust, Tuning' started by Phils15GT, Aug 18, 2018.

  1. Phils15GT

    Phils15GT Well-Known Member

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    Debating on getting flex fuel tune for the luxury of swapping back and forth should I find myself without an E85 station.

    With the flex fuel tune and a full tank of E85, is there a lot left on the table power wise being it is a FF tune and not 100% dedicated e85 tune?
     
  2. Gojr47

    Gojr47 Well-Known Member

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    Check out this video by Alex from Lund. A FF tune won't be as aggressive as an e85 tune.

     
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  3. HardWork

    HardWork Well-Known Member

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    Depends on your e-85 quality in your area. Flex fuel is a milder tune makes good power but timing is brought in slower. E-85R tune if every thing checks out with your logs they bring in the timing a lot earlier. I am still on stock tires but when I run e-85R tune back end likes to kick out 1st and second. If you are getting the tune from lund you can get the FF tune and ask them to write a straight e85 tune.
     
  4. Burkey

    Burkey Well-Known Member

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    The gap in performance from flex to full e85 tune isn’t anywhere near as crazy as 93 to flex obviously but it IS worth it.
    As other have said, it’s mostly in the bottom/mid range.
    Would it be quantifiable on the strip? Maybe, maybe not.
    The butt dyno says it’s absolutely worth it when you’re daily driving though, having that snappy timing coming in nice and early.
    Please bear in mind that my comments are based on the fact that I’ve never used e85 with an ethanol content below 85%.
    Typically it’s been 88-92
    YMMV
     
  5. OP
    OP
    Phils15GT

    Phils15GT Well-Known Member

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    Thanks for the replies. As much as I drive the car, think I'll go with full E85 tune.
     
  6. Zinc03svt

    Zinc03svt Well-Known Member

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    Once you go straight e85 you will not want to go back. The 1500-4000 rpm torque in everyday driving is night and day to pump gas.
     
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  7. thehunterooo

    thehunterooo Well-Known Member

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    Yeah no point in running the flex honestly if the E85 is good. I honestly didn't notice much of a difference between the two when actually driving the car but at least you don't have to worry about it learning and locking in at the wrong number if that is what the flex is doing. If you get caught without E85 you can just load the flex. I have now gone about 1k miles on the race tune now and it has been great.
     
  8. Myshelby3425

    Myshelby3425 Well-Known Member

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    What is the range or least % of e85 content that can be ran safely on the E85R tune?

    I just recently switched over to Flex and took the tank down to 0 and drove a bit after that. I was able to pump 15.95 gallons of e85. Wasn’t sure whether to wait for next tank or test out the e85R tune with this tank.
     
  9. HardWork

    HardWork Well-Known Member

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    Valid point I decided to take a break on the race tune run some 91 through for lubrication. Changed to FF tune with 20 miles to go. Pumped 91 first tank read 47% alch let the idle for 20 min still didn't learn the percentage until I drove for about 3 miles. Here is the problem when driving it went to 56%. Next tank of 91 I let the car idle with me reving for 10 and idle for 20 min it never learned. The car showed 15.2% alch. I had to leave so I drove never rev over 3k half a mile it learned but it learned at 24.8%. I am sending a message to lund to see if this can be fixed in the tune or is this just the nature of the widebands. When getting on it I noticed 2.3 on the knock when over 5K. Could have been a bad tank from shell but better safe then sorry. I add some lucas octane booster and the knock went away. So I am not sure if it was bad gas or the fact that the car read more alch then whats in it or both.
     
  10. Zinc03svt

    Zinc03svt Well-Known Member

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    You can add the lucas upper cylinder lubricant while on straight e85. Why mess with switching back? Lol.
     
  11. V8EATR

    V8EATR Well-Known Member

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    My car on the E85 race tune vs the flex saw about 2* more total timing and as high as 4* more throughout the pull. How much was it worth? Hard to say but I would say it worth it.
     
  12. thehunterooo

    thehunterooo Well-Known Member

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    for more info about the tunes.

    Yeah if it was that empty I would just run the flex for a few gallons and then switch.
     
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