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Thread: 7747 Highway Mode?

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    7747 Highway Mode?

    I have seen a highway mode patch from a long time ago. First I cn't figure out how to use it and second I am not sure I need it with todays technoligy, mainly software like TunerPro.

    Research shows the technoligy for hiway mode is in the 7747 but goverment said no because it ran outside of 14.7 to one AFR

    My 2WD Suburban has a 7747 with overdrive trans and I think this would help MPG. Some of the research found articles written back in 2000 that told how it works but cooling pistons could be affected as it runs leaner so hotter and the cooling system just does not have the effect or capibilaty to cool pistons. This is the job of oil. Cooling system handles the cylinder walls. Point is this truck came with from the factory an oil cooler. Nice stacked plate one at that with hydralic fitting lines to adapter at oil cooler. But the transmission came with an old technoligy style finned over tubing type, so I guess GM knew of the technoligy back then but had to use up old stock finned over tubing coolers for the trans while oil got the new tecnoigy stacked plate cooler.

    So point in my rant was oil has good cooler to help piston heat when using the hiway mode.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Re: 7747 Highway Mode?

    IIRC, the values are not only present, but enabled if you check the right boxes...

    however, i believe the point of the patch was to bypass the knock sensor test to allow highway fuel without the test being done?

    i'm not too certain though, the C3 ECMs aren't my area of study.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    Re: 7747 Highway Mode?

    Yeah I remember reading that about the patch, that it did away with the Knock Test.

    Is this an important issue? Seems to make the motor Knock on purpose is not good. But may be a setting point which would be good?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Re: 7747 Highway Mode?

    setting point? we have such different terminology.

    it's an effective way to test the sensor, but yes, it is a bit concerning. some of the later masks simply check to make sure the knock sensor is floating around 3900 ohms over a certain time period, too much or too little resistance constantly indicates that the sensor or it's circuit is a problem.

    GM OBD2 does the same thing IIRC.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    Re: 7747 Highway Mode?

    Quote Originally Posted by RobertISaar
    setting point? we have such different terminology.
    OK we all know you are more experianced then me, and I am glad I made you laugh! I do enjoy making people laugh!

    But I don't get it? What is correct term? Or how far off am I by discribing it this way? Or why did I make you laugh?

    I know my next post is going to have an smiley...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Re: 7747 Highway Mode?

    Quote Originally Posted by EagleMark
    Seems to make the motor Knock on purpose is not good. But may be a setting point which would be good?
    i'm just not certain of what exactly you're describing here.... "setting point" meaning an adjustable value?

    also, more experienced? not likely, it's probably just fresher in my mind.... i am only 22 after all.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    Re: 7747 Highway Mode?

    Quote Originally Posted by RobertISaar
    Quote Originally Posted by EagleMark
    Seems to make the motor Knock on purpose is not good. But may be a setting point which would be good?
    i'm just not certain of what exactly you're describing here.... "setting point" meaning an adjustable value?

    also, more experienced? not likely, it's probably just fresher in my mind.... i am only 22 after all.


    OK you made me laugh! I had bought my first TBI EFI Chevy about the same year you were born!

    It was the first year TBI chevy pick up truck and the last and only year the old body style was used for the pick up truck. 1987 Chevy 5.7L OD trans, 2WD short box. Man I wish I still had that! Red too!

    Oh, I forgot...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Re: 7747 Highway Mode?

    Quote Originally Posted by RobertISaar
    i'm just not certain of what exactly you're describing here.... "setting point" meaning an adjustable value?
    Yeah I guess I was describing an adjustable value STARTING POINT! Meaning it would do a knock test and come out with "A" when it checked last time you may have been at a different altitude or using hi test and it checked and started with "B".

    Do you happen to know exactly how this knock test works or what it is trying to accomplish?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Re: 7747 Highway Mode?

    how it works: when above a certain coolant temp (close to 200*F), and above a certain TPS% and engine speed, the ECM will add up to ~10* of advance in an attempt to cause knock where it "knows" knock should happen consistently if it adds enough advance. it will start at ~2* added, then add another 2*, then keep going until it sees knock, then it will back it all off and filter in knock retard.

    now, if it gets to the maximum knock it can add and still no knock, it will either set the trouble code for the knock sensor, or it will set a flag and try again later, i can't remember the specifics of $42. there's a really good post about it on TGO that i haven't been able to find...

    if the test passes, it sets a flag indicating that the test has passed and deems the knock sensor good, and then highway fuel is allowed.

    or at least that's how it was explained to me a few years ago. i prefer the way it works in $A1: get above a calibrated MPH, then as long as you don't add enough throttle to get into power enrichment, highway fuel is enabled.

    EDIT: and of course, the $42 patch bypasses the requirement for the knock sensor tst to have passed to allow highway fuel.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    Re: 7747 Highway Mode?

    Can this patch be done by just changing some hex code? Or is it a computer thing?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Re: 7747 Highway Mode?

    of course it's a computer thing. :D

    all patches are hex code anyways. if you can find the patch file or anything related to it, i can likely get it working for you.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    Re: 7747 Highway Mode?

    Yup I got the patch downloaded and had read some instructions somewhere else but it was like doing dos and I suck at dos, it's not dos though...

    so you can do this to the bin file? That's what I meant by hex, I could probably change hex, maybe... I do php and cgi files all the time in edit pad, like notepad, would that work or do you need a hex editor?
    Attached Files Attached Files

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Re: 7747 Highway Mode?

    i see... they're S19 files.

    not too much of a problem.

    there are actually two patches in there.

    i can make a quick rundown:

    crap, maybe not.... the s19 patch program doesn't like my 64 bit OS...
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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    Re: 7747 Highway Mode?

    Yeah I know nothing of that type stuff. I also followed directions from another thread and no worky. Maybe it was my 64 bit system?

    The 2 patches were removing knock test and enabling hi way mode.

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

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    Re: 7747 Highway Mode?

    okay.... the actual .s19 files seemed to have hex code in them that gets patched in...

    open up tunerpro, get into the hex editor:

    make a backup copy of your BIN, go to 0BD5 and start typing:

    96 0A 8A 80 97 0A 20 12 C7

    that bypasses the knock sensor test....

    now go to 0B04:

    96 21 81 80 22 05 7F 00 78 20 25 96 78 B1 D0 25 25 1E 96 26 81 AF 22 18 D6 03 CA 02 D7 03 44 CE DB 2B BD FB 49 20 11 A1 A1 A1 9F 9C 9B 9A 9A 9A

    and that's the rest of the patch. now, coolant temp is checked against the value found at $B07, if lower, highway fuel is disabled. this is in additon to the checks made for the values found at $025(minimum time with all conditions met before allowing) and $024(minimum MPH to allow) for highway spark. $B19 is then checked to see if MAP is under the maximum limit to allow highways fuel/spark. then your actual highway fuel target AFR table will be found at $B2B, it's 9 values long.

    want me to put all of this in an XDF for you?
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


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