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    Fuel Injected! TheApocalyptican's Avatar
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    DFCO Info

    Looking into adjusting the DFCO to turn on a little more often. I get the basic idea of how everything works but there are some things that are confusing. 1st off, after logging with it enabled, I saw a BPW MS drop to 0.xx at around 55mph after letting off from 70mph. I've read that the BPW MS should drop to 0 when DFCO engages. Does this 0.xx qualify for 0, or should it actually be a flat 0.00? If it doesn't qualify, is this just DE then, and not DFCO?


    The other part I am confused with is why the DFCO RPM to disable, and Map to disable scalers are maxed out. RPM is at 6375 which seems to me like it would conflict with the RPM threshold table. And the Map is 99.69, which would seem to conflict with the Map threshold table.

    Edit: 7747 ASDU $42
    Last edited by TheApocalyptican; 04-19-2013 at 02:32 AM.
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    RIP EagleMark's Avatar
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    Quote Originally Posted by TheApocalyptican View Post
    Looking into adjusting the DFCO to turn on a little more often. I get the basic idea of how everything works but there are some things that are confusing. 1st off, after logging with it enabled, I saw a BPW MS drop to 0.xx at around 55mph after letting off from 70mph. I've read that the BPW MS should drop to 0 when DFCO engages. Does this 0.xx qualify for 0, or should it actually be a flat 0.00? If it doesn't qualify, is this just DE then, and not DFCO?
    Post a log so I can see it. So it actually says 0.xx? Or is XX a little number?

    Quote Originally Posted by TheApocalyptican View Post
    The other part I am confused with is why the DFCO RPM to disable, and Map to disable scalers are maxed out. RPM is at 6375 which seems to me like it would conflict with the RPM threshold table. And the Map is 99.69, which would seem to conflict with the Map threshold table.
    These are some of the last things I'm working on for the next/last version. I'm not sure they are all worded correctly and none have ever had comments in XDF description.

    IIRC the RPM to disable cutoff and MAP to disable cutoff should read RPM/MAP to Disable, meaning it is always on until that point.

    The ones to adjust are the three tables "DFCO - Upper/Lower RPM/MAP/MPH Threshold"

    You seemed to have found one of the last things I haven't tweaked to death and fully understand in $42!

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  3. #3
    Fuel Injected! TheApocalyptican's Avatar
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    The 0.xx were small numbers. They were in the 0.90's, 0.80's, or it seemed to bottom out at 0.40 It only seemed to be doing it from higher speed decel's, not medium speed ones. Log is kinda long, as I was just kinda checking everything out. Still gotta do more VE tuning. The 70mph decel is just under 30 mins in. While you're looking...do the vac/map readings seem low/high to you? Seems to me like they are more where I'd expect them early on, and drop after being warm for a while.
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    Last edited by TheApocalyptican; 04-19-2013 at 04:45 AM.
    '90 Suburban w/ pretty much stock 350 TBI, 7427 ECM Conversion, sadly sold several years ago
    '95 K2500 Suburban w/ soon to be 400HP 454

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    RIP EagleMark's Avatar
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    I'm not sure that is DFCO and maybe just Decel. You can see the Async fueling flag come on when this happens.

    Not much idle time at end of log, always leave some in drive and park time at end of log, it helps. Like for instance best I can tell at idle your TPS voltage is .98 IAC counts were 10 and idle was 1100, so not so good. During that DFCO/Decel TPS voltage was also .98. Should be closer to .54, so either the throttle blade adjustment is way off or throttle is sticking open?

    I have to do a lot more work in testing and going through dis-assembly to get the description right for all the DFCO settings, not going to happen soon but on my list.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Fuel Injected! TheApocalyptican's Avatar
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    Async comes in during DE, or DFCO? Wasn't clear to me which you meant.
    .98 is currently where the tps sits. 0.98 is a little high. IAC was dropping to 0, so I just went thru the iac reset again with a helper, and dropped it about 3/8 to 1/2 turn, so the tps should be lower now. I've never been able to get it to adjust all the way to .54. Need to get some kind of dremel bit or something in order oval out the tps holes and adjust. I haven't been to worried about it due to reading that the tps is looked at when started, and that the reading is considered 0%.

    The RPM/Map to disable being the way you said is kind out what I figured. It was just the wording of the scaler that was messing with me.

    On a completely separate thing I've been curious about, how does the ECM know how much fuel to command when in open loop for any reason? I get that it is based on an AFR table, but I didn't think the o2 is read in open loop, so how does it calculate how much fuel is needed?
    '90 Suburban w/ pretty much stock 350 TBI, 7427 ECM Conversion, sadly sold several years ago
    '95 K2500 Suburban w/ soon to be 400HP 454

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    Async comes in during DE, or DFCO? Wasn't clear to me which you meant.
    I think Decel, not really sure about DFCO if it's even working, like I said you got me on one I have not worked on heavily. SO take it with a grain of salt, may be another internet rumor by the time I'm done figuring it out for certain?

    .98 is currently where the tps sits. 0.98 is a little high. IAC was dropping to 0, so I just went thru the iac reset again with a helper, and dropped it about 3/8 to 1/2 turn, so the tps should be lower now.
    Check at end of a drive to see where IAC counts are. Get a log of idle at end of log, seems to high, something is wrong or not set right?

    On a completely separate thing I've been curious about, how does the ECM know how much fuel to command when in open loop for any reason? I get that it is based on an AFR table, but I didn't think the o2 is read in open loop, so how does it calculate how much fuel is needed?
    "Open Loop - AFR vs Temp" is the starting point for Open Loop fueling.

    Your other question of low vacuum?High MAP? Seems it is even at highway speeds? Have you set base timing to 0? Any vacuum leaks? Seems like a possibility with the high idle as well?

    Start a log when fully warmed up, drive steady throttle position, 10% 20% etc, one WOT run and let it idle at end of drive in gear a minute and in park a minute. With that I may be able to help you out.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

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