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Thread: Math Wizzards - BEN Factor IAT correction

  1. #21
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    Quote Originally Posted by GMPX

    Another idea, Paul, can you put a 'bug' in the software to force metric only, then you guys might just see the light :wink:

    Cheers,
    Ross
    Metric is a helluva lot easier once you're used to it. My .02.


    Cheers,
    joel

  2. #22
    Lifetime Member TAQuickness's Avatar
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    Quote Originally Posted by GMPX
    I too have been tearing my hair out with this issue.
    Before I go into why I think this happens basically you just need to be aware of the problem and try to tune with consistant IAT values...
    Cheers,
    Ross
    I've got no hair, so we're close to the same boat

    I'm pretty sure the PCM is doing what it's supposed to, and that the problem is not related to the PCM and environmental conditions.

    I think the problem is how we are applying the BEN factor to the VE table (not a bug in the software by anymeans).

    This relates directly to the screen shots I posted. All of the data we are logging is average data. So to apply the avg BEN factor to the VE table correctly, we would need to apply it to the respective avg RPM and avg MAP kPa. In most cases, this means the BEN factor would need to be applied to an interpolated value in the VE table.

    If you look at the screen shot's in my previous post, you will see, the BEN factor is near identical from map to map when the average RPM AND MAP kPa is near identical.

    However, if you look real close, there does appear to be an anomaly to this theory.

    Another thing I have noticed. Of the 4 log's, afternoon 1 is inconsistant with the the following 3 logs. This makes me think the PCM, despite being in OL SD, is still going through some sort of a learning process.

    Degrees C, Degrees F, you say po-tay-toe, I say po-tah-toe. One's thing for sure, it's effing hot in Houston right now!

  3. #23
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    I've been open loop about 2 years.
    My idle AFR has always leaned out (FJO Wideband) as the intake air temp increases.
    I had to rescale the maf in the appropriate lower hz. in order to get the AFR down around 14.7 at idle (narrow LSA cam).
    With the idle AFR in the 14.7 range the IAT seems to have less of an effect than it did when it was in the 15-16:1 range.

    FWIW.

    Cheers,
    joel

  4. #24
    Lifetime Member TAQuickness's Avatar
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    Quote Originally Posted by bink
    My idle AFR has always leaned out (FJO Wideband) as the intake air temp increases.
    Scratching my head, but as IAT goes up, shouldn't your AFR go rich, not lean?

    I'll be collecting some new data today. Hopefully the results will be consistant.

  5. #25
    Lifetime Member SSpdDmon's Avatar
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    Quote Originally Posted by TAQuickness
    Quote Originally Posted by bink
    My idle AFR has always leaned out (FJO Wideband) as the intake air temp increases.
    Scratching my head, but as IAT goes up, shouldn't your AFR go rich, not lean?

    I'll be collecting some new data today. Hopefully the results will be consistant.
    That depends on how the temp. variable affects the equation the PCM is using to calculate fueling. If they just got close with their curve based on an expected range for operating temps, it's possible the further you move from the "sweet spot" the worse the fueling calcs. get. After seeing what my real VE table looks like versus what they set it at from the factory, I'm hesitant to believe there is much in our PCM's that is spot on. Ideally, you're thinking along the right path that as the air get's warmer, it becomes less dense and therefore requires less fueling. But, because IAT is a variable in the equation, it shouldn't matter assuming the equation is correct. But, I doubt that's the case. Too bad we couldn't tweak that in EFI Live...

  6. #26
    Lifetime Member TAQuickness's Avatar
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    Quote Originally Posted by SSpdDmon
    Too bad we couldn't tweak that in EFI Live...



    I just got done with my second log after a new tune. I'm really starting to think the it takes the PCM a little while, a drive cycle or 2, to adjust after flashing.

    Paul, Ross, and/or who ever else gets way into it - Does the PCM store any history of barometric pressure or IAT or other environmental condidtions?

  7. #27
    Guess who's back!!!! Black02SS's Avatar
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    Quote Originally Posted by TAQuickness
    Quote Originally Posted by SSpdDmon
    Too bad we couldn't tweak that in EFI Live...



    I just got done with my second log after a new tune. I'm really starting to think the it takes the PCM a little while, a drive cycle or 2, to adjust after flashing.

    Paul, Ross, and/or who ever else gets way into it - Does the PCM store any history of barometric pressure or IAT or other environmental condidtions?
    I know what you are saying. On my personal car, I will start off from a cold start at about 63-64psi of fuel pressure. After the car is warmed up and has been driven for an hour or so, the pressure drops back down to the 58-60 range. Depending on where you tune the car at, it will effect the AFR I have seen.

  8. #28
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    Quote Originally Posted by TAQuickness
    Quote Originally Posted by SSpdDmon
    Too bad we couldn't tweak that in EFI Live...



    I just got done with my second log after a new tune. I'm really starting to think the it takes the PCM a little while, a drive cycle or 2, to adjust after flashing.

    Paul, Ross, and/or who ever else gets way into it - Does the PCM store any history of barometric pressure or IAT or other environmental condidtions?
    Hmmm..... the idle airflow is stored and is temp referenced. I know nothing about the code/calibration though. Maybe it has something to do with idle airflow and not he fueling. Has anyone scanned pulsewidth?
    Just a thought.

    Cheers,
    joel

  9. #29
    Lifetime Member TAQuickness's Avatar
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    I believe I had the injector pulse width in the 4 logs the screen shots came from. I'm transistioning to a new laptop at the moment so it will be a while before I can take a look at the logs...

  10. #30
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    Quote Originally Posted by TAQuickness
    I believe I had the injector pulse width in the 4 logs the screen shots came from. I'm transistioning to a new laptop at the moment so it will be a while before I can take a look at the logs...
    gojo has said many times Idle AirFlow Parked {B4308} , if not corrected with modified TBs, will often skew the airflow at idle. We found this to be true with my car previously.

    After thinking about this....... I think this is probably the case - if Idle pulsewidths are unchanged. Higher IATs result in greater opening of the AirFlow Parked {B4308} - you can check it by scanning Desired IAC steps or g/sec. Like most of these parameters there is a sweet spot relation between AirFlow Parked {B4308} and Idle Airflow {B4307}.
    Nick and gojo are the main gurus in regard to this. (Yes nod Emoticon here).

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