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Thread: Tuned and now high LTFT

  1. #1
    Tuner in Training
    Join Date
    May 2019
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    12

    Tuned and now high LTFT

    I had my L99/LS3 engine tuned and it has great power but I have noticed that the LTFT's are around +12% idle and during cruise its anywhere from +7 to +18% depending on RPM. I'm purchasing HP Tuners and would like to get the LTFT's down to the low negatives or as close to zero as possible. Could I do that by just adjusting the maf calibration table? (Before the tune it was -10% pretty much across the rpm range with new cam.)

    I thought about putting in a Stock LS3 Maf calibration table but not sure how drastic the change would affect engine. Basically this engine is a L99 engine with a camshaft that was made to remove DOD but retain VVT. (Duration 200/209 Lift .528/.528 115+7 LSA) Any advice greatly appreciated. Included both stock and tuned files in case that helps. (Note both files are with the engine having new camshaft)
    Attached Files Attached Files
    Last edited by reborn74; 05-28-2019 at 02:31 PM.

  2. #2
    The tune is setup to be MAF only above 2000 rpm and they did not touch VVE/idle. If you want it "perfect" you will need to spend hours doing VVE tuning and also redoing MAF.
    Last edited by Jeff7577; 05-29-2019 at 02:19 PM.

  3. #3
    Tuner in Training
    Join Date
    May 2019
    Posts
    12
    Thank you. I see that now when I did a compare between the two files. Would putting it back to stock (MAF only above 4000) be a better option?
    Also I have compared my airflow vs frequency setting to a bone stock L99 and its way different than what I have. Would putting it back to stock help and /or would I have to learn how to tweak it for my setup?

  4. #4
    Just setting it back to 4000 should get it back closer to the negatives while driving which is preferable to it adding fuel. They never touched VVE so it should run more like it did before the tune while under 4000.

    Do you have a wideband?

  5. #5
    Tuner in Training
    Join Date
    May 2019
    Posts
    12
    Thank you!
    I will set it to 4000 and see how it runs. I don't have a wideband installed. I have been doing some research and I will invest in a wideband (recommendations welcomed) and install it on the driver side after the O2 sensor and before the H pipe. (This engine and transmission is in a Nova)
    Where is the VVE?

  6. #6
    VVE is the set of tables under Airflow-Speed Density-VE Coefficients. You modify it by using the Virtual Volumetric Efficiency Table Editor in HP Tuners under the Edit menu at the top.