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Thread: Changed my IFR...AFR Is erratic

  1. #1
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    Default Changed my IFR...AFR Is erratic

    When my car was tuned previously, the tuner used the following values for the IFR
    0 7.7656
    5 7.7891
    10 7.8438
    etc

    Using the spread sheet listed here I get:

    0 8.7295
    5 8.7839
    10 8.8380

    I plugged those numbers in and according to the gauge the AFR went Real lean, I switched it back.
    Which set of numbers would be considered correct? Is it wrong to put an incorrect number in the IFR tables and tune around it? I understand that changing the flow rate would change the AFR, but if my commanded AFR is matching my gauge with the original numbers, does that mean those numbers are correct?
    98 WS6, M6, 02 PCM, CO3, SD 2 Bar tune, 416 D1SC Procharger, 73# Injectors, Patriot Lq9 heads, 232 int 240 exh. Lift .595 int .608 exh 115.. header, Intake, AEM WB.

  2. #2
    Lifetime Member SSpdDmon's Avatar
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    Sounds like he tuned your AFR using the IFR table. This is a common method of tuning as most pro's don't follow the VE/MAF tuning process that we do. Entering realistic flow numbers into your IFR table will require you to tune the MAF and VE accordingly.

    An IFR tune can still achieve commanded AFR=actual AFR. It just does so using the stock MAF curve and a bogus injector flow rate table instead of an accurate IFR table and modified MAF curve.

  3. #3
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    Hmmm No MAF here, I bet that really messed things up. I hate to ask this, but would it be better to plug in correct IFR numbers and start over on the VE table? I am assuming that is all I would need to change. Is the IFR tune just faster? Sorry I am asking so much, as I start to see how things interact, I think myself into a corner....damn ADD.....I am going to do a search on IFR tunes and see where that logic is. Thanks
    98 WS6, M6, 02 PCM, CO3, SD 2 Bar tune, 416 D1SC Procharger, 73# Injectors, Patriot Lq9 heads, 232 int 240 exh. Lift .595 int .608 exh 115.. header, Intake, AEM WB.

  4. #4
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by zapp168
    Hmmm No MAF here, I bet that really messed things up. I hate to ask this, but would it be better to plug in correct IFR numbers and start over on the VE table? I am assuming that is all I would need to change. Is the IFR tune just faster? Sorry I am asking so much, as I start to see how things interact, I think myself into a corner....damn ADD.....I am going to do a search on IFR tunes and see where that logic is. Thanks
    That's what we do... recompute the IFR and then do Auto VE.

    IFR tune is much quicker than VE tune, but the PCM is being tricked under most conditions
    (actual AFR not equal to commanded AFR).

    Important: if you change IFR and/or VE, monitor what is happening with your wideband.

  5. #5
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    OH YA.... when I changed the IFR table I went real lean real quick! If just re-calculating the VE table with the correct IFR will make the tune "more correct" I would rather go that route. Again...Joe...Jeff...Thanks.....you guys work for EFIlive or something ?
    98 WS6, M6, 02 PCM, CO3, SD 2 Bar tune, 416 D1SC Procharger, 73# Injectors, Patriot Lq9 heads, 232 int 240 exh. Lift .595 int .608 exh 115.. header, Intake, AEM WB.

  6. #6
    Joe (Moderator) joecar's Avatar
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    Zapp, you're welcome.

    Jeff and I are EFILive users, and I'm one of the forum moderators ("In charge of lost bolts").

  7. #7
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    Funny....you always seem to help me when I've lost my marbles...
    98 WS6, M6, 02 PCM, CO3, SD 2 Bar tune, 416 D1SC Procharger, 73# Injectors, Patriot Lq9 heads, 232 int 240 exh. Lift .595 int .608 exh 115.. header, Intake, AEM WB.

  8. #8
    Lifetime Member SSpdDmon's Avatar
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    One of the perks of using EFI Live I guess.

  9. #9
    Lifetime Member 5.7ute's Avatar
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    Zapp, if you look on redhardsupras blog he has a method of unscrewing a bad tune. Give that a read.

  10. #10
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    I will take a peek....Thanks...I think / hope this is just going to be some more VE tuning. The car does not run bad now, just rather have the correct numbers in there.....How did he pick those IFR numbers?
    98 WS6, M6, 02 PCM, CO3, SD 2 Bar tune, 416 D1SC Procharger, 73# Injectors, Patriot Lq9 heads, 232 int 240 exh. Lift .595 int .608 exh 115.. header, Intake, AEM WB.

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