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Thread: TBSS MAF Over Reporting Airflow

  1. #11
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by LastCall View Post
    Yes, see post 34.

    Correct IFR tables for LS3/LS7 injectors in Gen III
    https://forum.efilive.com/showthread.php?t=11498
    Quote Originally Posted by LastCall View Post
    Yes, 36 at 3 bar. I converted the values with a spreadsheet based on 4 bar pressure. I'll post the tune later.

    One note, I could not find injector voltage offsets, only in gen 3 format. And I read you couldn't copy, paste, and interpolate between 3 and 4 voltages because there like values don't correspond to one another. Redhardsupra posted about it. That still valid?
    Yes, correct, the interpolation is not linear, but is as square root...

    linear interpolation between cells is an approximation, I haven't checked how close it is, but it's not far off as long as the interpolation is only between adjacent cells.

  2. #12
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    Thanks for the input Joecar.

    I was referring to the voltage table and interpolating there. So it sounds like I should I take known values and interpolate between them to fill in the table?
    00 Silverado Z71, LQ9 w/ LS3 heads, BTR cam, Whipple 2.9@8#, 4l80E

  3. #13
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by LastCall View Post
    Thanks for the input Joecar.

    I was referring to the voltage table and interpolating there. So it sounds like I should I take known values and interpolate between them to fill in the table?
    Yes, same applies to voltage table.

  4. #14
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    Quote Originally Posted by joecar View Post
    Yes, same applies to voltage table.
    Going to try that, thank you sir.

    Do you think its possible the engine could want that much airflow at idle though?

    Hard to get things dialed in when there is not good injector data out there!!
    00 Silverado Z71, LQ9 w/ LS3 heads, BTR cam, Whipple 2.9@8#, 4l80E

  5. #15
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by LastCall View Post
    ...

    Do you think its possible the engine could want that much airflow at idle though?

    ...
    Not physically, but mathematically maybe... this is what happens when the modelling is off.

  6. #16
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    Here is a current copy of the tune as well as a link to the injectors. I did not adjust the injector voltage offsets yet, they are stock still.

    http://www.fuelairspark.com/fas/8-36...injectorshtml/

    Also included is a short log at idle. I did not adjust for the -12% error with the tune I attached. So the numbers at idle htz would be about 12% lower than reported.

    Could the voltage offsets be causing the over-reporting of the airflow?
    Attached Files Attached Files
    Last edited by LastCall; June 29th, 2016 at 08:11 AM.
    00 Silverado Z71, LQ9 w/ LS3 heads, BTR cam, Whipple 2.9@8#, 4l80E

  7. #17
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by LastCall View Post
    Here is a current copy of the tune as well as a link to the injectors. I did not adjust the injector voltage offsets yet, they are stock still.

    http://www.fuelairspark.com/fas/8-36...injectorshtml/

    Also included is a short log at idle. I did not adjust for the -12% error with the tune I attached. So the numbers at idle htz would be about 12% lower than reported.

    Could the voltage offsets be causing the over-reporting of the airflow?
    Only if they are sufficiently far out (I don't know how far they have to be), and if they are baked into the MAF and VE tables.

  8. #18
    Joe (Moderator) joecar's Avatar
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    What is the IFR of those injectors at 58 psi (4-bar)...?

    I calculated 5.24 g/s (41.6 lb/hr).... this would be about 5% different than your B4001 400 kPa cell.
    I calculated that the 480 kPa cell should be 5.24 * sqrt(480/400) = 5.74 g/s.

    Your B4001 400 kPa cell says 5.0547 g/s...
    based on this I calculated that your 480 kPa cell should say 5.0547 * sqrt(480/400) = 5.537 g/s
    your 480 kPa cell says 5.3391 g/s which is about 3% off.

    So overall your 480 kPa cell is about 12% off.

    So the in-between cells are off by some amount between 5% to 12%.

  9. #19
    Joe (Moderator) joecar's Avatar
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    Since your IFR is lower than what the injectors flow, then if the MAF were corrected like this it would be under-reporting...

    so, from looking at Idle after LTFT MAF adjustment.efi I think try this: bring your MAF table down by 10% and see what the LTFT's say.

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