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Thread: Not reading correct e85 %

  1. #1
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    Not reading correct e85 %

    Updated app. And now e85 % is wrong went from e85 to e40. And nothing changed
    Also tested fuel to make sure.

  2. #2
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    Any updates. - filled tank again and tested e85. Still reads. Low a amount
    This is on Ford Mustang 2019 gt
    Last edited by paulsmithsr; 02-09-2020 at 10:05 PM.

  3. #3
    have you right clicked and verified what display units are available? maybe requires another unit of display?

  4. #4
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    Yes tried all

  5. #5
    Senior Tuner LSxpwrdZ's Avatar
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    Depending on the vehicle and the flex fuel type being used this can happen when a physical flex sensor isn't present. Virtual flex fuel like Dodge, Ford and most GM's use fuel trim data to determine ethanol content. When re-writing the tune sometimes that setting can get reset and display the wrong content. Now if there is a physical sensor in the system and it's still reading off then you likely have a PID issue within the scanner or the content hasn't fully learned back through the buffer time preset in the tune.
    James Short - [email protected]
    Located in Central Kentucky
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    2020 Camaro 2SS | BTR 230 | GPI CNC Heads | MSD Intake | Rotofab | 2" LT's | Flex Fuel | 638rwhp / 540rwtq
    2002 Camaro | LSX 427 | CID LS7's | Twin GT5088's | Haltech Nexus R5 | RPM TH400

  6. #6
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    sweet--- yes its a ford virtual flex thanks for response

  7. #7
    any idea what math is used in virtual flex fuel to get the ethanol content output value?

    with this, i bet we could build out using math parameters in VCM Scanner

    i read that when the computer senses fuel was added, for a given amount of time after fill up the ECU compare previous fuel trims with new fuel trims and estimate ethanol content from this using a calculation.

    EDIT:
    found more info.


    https://forum.hptuners.com/showthrea...l=1#post514950
    E85 Flex Fuel Description

    E85 compatible vehicles no longer use an alcohol sensor to determine and adjust for the alcohol content of the fuel in the tank. Instead, the vehicle calculates the alcohol content of the fuel through measured adjustments.

    The ethanol calculation occurs with the engine running after a refueling event has been detected via a measured change in the fuel level sender output. The virtual flex fuel sensor (V-FFS) algorithm temporarily closes the canister purge valve for a few seconds and monitors information from the closed loop fuel trim system to calculate the ethanol content. This logic executes several times until the ethanol calculation is deemed to be stable. This may take several minutes under low fuel flow conditions such as idle, or a shorter time during higher fuel flow, off-idle conditions.

    Air-fuel ratios and the corresponding ethanol percentage are updated following each purge-off sequence. The fuel alcohol content percentage value can be read on a scan tool.

    When an E85 compatible vehicle is built, an ECM or PCM replaced, or if the learned alcohol content has been reset with a scan tool the fuel system will need to contain ASTM gasoline with 10 percent or less ethanol content.

    A minimum of 11 liters (3 gallons) must be put in the tank in order for the vehicle to recognize a re-fueling event. It is not necessary to turn the ignition OFF in order to have the re-fueling event recognized, however local safety regulations should be followed.

    After the re-fueling event, the system registers the amount of fuel that was added, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines if the fuel added was either ASTM Gasoline or ASTM E85. Based on that determination, the system adjusts to the expected alcohol mix in the fuel tank, and then the fuel trim and O2 sensor activity fine tunes the adjustments. The system must remain in closed loop in order for this adjustment to occur. Numerous short trips after switching from gasoline to E85, or E85 to gasoline, can result in driveability symptoms due to the inability of the system to adjust for fuel composition by not attaining closed loop
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    Last edited by hachiroku; 02-12-2020 at 11:49 AM.