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Thread: 2 bar SD VE tuning

  1. #1
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    2 bar SD VE tuning

    When tuning the ve with a 2 bar sd os do you try and isolate the lower and upper parts of the ve table, 0 to 105 then 105 and up when in boost. I ask this as the way I see it is if your tuning the whole table when you are in the lower parts say 0 to 80, and TPS engages PE and you are using AFR % error histo and copying and pasting, you will get false readings in the lower parts. Should I tune the lower part with LTFT or AFR 105 % error and then tune the 105 and up by just copying and pasting 105 and up. Or is there a better way, dose any know if VE, PE, BE have any transition or combine together at all.
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  2. #2
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    This is what is confusing me I don't want PE or BE making changes to the VE down low on the VE. I have read this and this is confusing me as I cant find where FTC cells 20,21,22 on the scanner. How do I monitor these cells.


    The LTFT uses cells to “cover” the VE table. The current cell in use is called the Fuel Trim Cell (FTC). There are 16 cells (0 – 15). Cells 20,21,22 are used by the VCM when it does not want to make a permanent correction to the VE table values (examples would be Decel Fuel Cutoff, Power Enrich Fuel, Charcoal Canister Purge off).

    By monitoring the current LTFT cell number (FTC) in the scanner, you can make a decision of when to ignore the LTFT correction. Do not use the histogram logged corrections for cells 20,21,22.

    LTFT cells are “placed” on the VE table by using the LTFT Low, Mid High boundaries on the Closed Loop fuel tab.
    The RPM boundaries on the sample are 1300 RPM, 2500 RPM, 3500 RPM
    The Map boundaries on the sample are 32 kPa, 56 kPa, 80, kPa

    A graphical representation of this layout is shown in the figure below.
    The RPM Boundary values are shown in red, the MAP boundary values are shown in blue. The lines are for display purpose only and do not appear on the VE table.





    LTFT cells are also “placed” on the Histogram LTFT table by using the LTFT Low, Mid High boundaries on the Closed Loop fuel tab. A graphical representation of this layout is shown in the figure below.
    The RPM boundaries on the sample are 1300 RPM, 2500 RPM, 3500 RPM
    The Map boundaries on the sample are 32 kPa, 56 kPa, 80, kPa

    The RPM boundary values are shown in red, the MAP boundary values are shown in blue. The lines are for display purpose only and do not appear on the histogram.






    STFT: stands for Short Term Fuel Trim. This is the VCM’s ability to make needed corrections quickly to the Air Fuel Ratio by monitoring the vehicles stock O2 sensors.
    The STFT corrections are instantaneous corrections and do not employ the use of cells, nor is it a permanent correction.

    The STFT Histogram keeps track of these changes so you don’t have to. The corrections displayed in the scanner are a + - % correction to the values on the VE table, zero being no change. They are to be considered a “fine tune” for the LTFT cell adjustments. Seeing as the LTFT is cell based and covers a wide area on the VE table, the STFT corrects the conditions within those cells.

  3. #3
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    This is what is confusing me I don't want PE or BE making changes to the VE down low on the VE. I have read this and this is confusing me as I cant find where FTC cells 20,21,22 on the scanner. How do I monitor these cells.


    The LTFT uses cells to “cover” the VE table. The current cell in use is called the Fuel Trim Cell (FTC). There are 16 cells (0 – 15). Cells 20,21,22 are used by the VCM when it does not want to make a permanent correction to the VE table values (examples would be Decel Fuel Cutoff, Power Enrich Fuel, Charcoal Canister Purge off).

    By monitoring the current LTFT cell number (FTC) in the scanner, you can make a decision of when to ignore the LTFT correction. Do not use the histogram logged corrections for cells 20,21,22.

    LTFT cells are “placed” on the VE table by using the LTFT Low, Mid High boundaries on the Closed Loop fuel tab.
    The RPM boundaries on the sample are 1300 RPM, 2500 RPM, 3500 RPM
    The Map boundaries on the sample are 32 kPa, 56 kPa, 80, kPa

    A graphical representation of this layout is shown in the figure below.
    The RPM Boundary values are shown in red, the MAP boundary values are shown in blue. The lines are for display purpose only and do not appear on the VE table.

    http://www.hptuners.com/help/gfx/vcm...ow_to_ve_1.jpg



    LTFT cells are also “placed” on the Histogram LTFT table by using the LTFT Low, Mid High boundaries on the Closed Loop fuel tab. A graphical representation of this layout is shown in the figure below.
    The RPM boundaries on the sample are 1300 RPM, 2500 RPM, 3500 RPM
    The Map boundaries on the sample are 32 kPa, 56 kPa, 80, kPa

    The RPM boundary values are shown in red, the MAP boundary values are shown in blue. The lines are for display purpose only and do not appear on the histogram.

    http://www.hptuners.com/help/gfx/vcm...ow_to_ve_2.jpg




    STFT: stands for Short Term Fuel Trim. This is the VCM’s ability to make needed corrections quickly to the Air Fuel Ratio by monitoring the vehicles stock O2 sensors.
    The STFT corrections are instantaneous corrections and do not employ the use of cells, nor is it a permanent correction.

    The STFT Histogram keeps track of these changes so you don’t have to. The corrections displayed in the scanner are a + - % correction to the values on the VE table, zero being no change. They are to be considered a “fine tune” for the LTFT cell adjustments. Seeing as the LTFT is cell based and covers a wide area on the VE table, the STFT corrects the conditions within those cells.

  4. #4
    Advanced Tuner Montecarlodrag's Avatar
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    You should not be tuning a boosted engine using LTFT. You need a wideband
    9 sec Montecarlo SS

  5. #5
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    I am using a wideband and AFR error histo, i just don't know if should disable any thing while tuning the ve. I have been looking every where and all i can find is info on tuning ve when running a maf and not a 2 bar sd custom os ve tuning.