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Thread: Tuning Individual Cylinder Fuel Trims

  1. #1
    Fuel Injected! Terminal_Crazy's Avatar
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    Tuning Individual Cylinder Fuel Trims

    I tried a different method on tuning the individual fuel trims yesterday.
    Originally going off the narrow band O2's i'd got the RHS set at 5% richer but the WB AFR bounced all over the place.

    So going off a comment i read the other day (Kur4o i think) about tuning them OL I got back from a good run.
    Cleared the data log and sat recording idle.
    Let it stabilize.
    Then every 500 logs cut a cylinder.
    Then recorded another 500 logs of idle as a base line.

    Loaded the logs into a spread sheet, selected each block of cylinder logs and recorded the average.
    If cyl 1 was from log AQ500 to AQ1000, I selected the range AQ525:AQ975 .This just removes cells where the AFR's settle down after swapping cylinders.
    Arranged the results Leanest to Richest average. (the leaner the result, the richer that cylinder must have been & vice versa).

    Pick one of the center cylinders (Cyl 3 as it's on the leaner side) as base cylinder
    Divide the base value by each average result

    leanest= 16.116 / 15.801 == 1.0199%
    richest= 16.116 / 16.489 == 0.9773%

    afr cyl
    15.801 2 LEANEST (Richest result) == 1.0199% 14.7 * this == 14.99
    15.941 7 == 1.0109
    16.113 6 == 1.0001
    16.116 3 base == 1.0000
    ----- ------------------
    16.212 5 == 0.9948
    16.323 8 == 0.9873
    16.332 1 == 0.9867
    16.489 4 RICHEST (leanest result) == 0.9773% 14.7 * this == 14.36

    These values multiplied by 14.7 shows a comparative spread of AFR ( 0.63) I was getting between cylinders.

    After running the car tonight & relogging this again with 1000 logs per cylinder the spread has dropped 14.99-14.36 to 14.97-14.50. (now 0.47)

    It doesn't look a massive amount but the cylinders are all within 2% of the base.
    The car idled noticeably better and smoother than the previous night.

    I'll try this a couple more times and see if the trims settle down any further

    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  2. #2
    Fuel Injected! Terminal_Crazy's Avatar
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    Update:

    This method doesn't seem to work now once you get the fueling back up from being rich.

    14.7 * 1.125 should top out around 16.5
    I was still idling at low 14's but with a cylinder cut it just ramps up and maxed out the Wideband after a few seconds.

    I'm currently playing with the injector adders ( see other thread ) to see it it improves the idle.

    Thanks
    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  3. #3
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    The trimming will probably be wrong at high throttle openings

  4. #4
    Fuel Injected! Terminal_Crazy's Avatar
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    Quote Originally Posted by delcowizzid View Post
    The trimming will probably be wrong at high throttle openings
    I’m trying to trim the idle.
    On the LT1 $EE there are two tables.
    TPS @0%. And TPS>0% and a TPS limit for the second table.

    Thanks
    Mitch
    '95 Z28 M6 -Just the odd mod.
    '80 350 A3 C3 Corvette - recent addition.

  5. #5
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    Oh nice feature

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