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Thread: LT1 Burst knock settings

  1. #1
    Fuel Injected!
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    LT1 Burst knock settings

    I have a burst knock issue on my 94 LT1 Stroker I would like to improve. When I built it, the compression came out higher than I wanted it to when I measured and assembled it and there wasn't an easy way to fix it. Because of that I run a Snow Performance water injection system in order to be able to use pump gas. It takes care of the detonation once I am in it, but I still have a burst knock issue when I hammer it. I believe this is because it just takes a moment for the Methyl alcohol to activate and reach its destination. After the burst knock it seems like it takes forever for the ECM to put the advance back in. I have found numerous Burst knock tables in tunerpro, but I am really not sure what to do with them. How do I get the computer to put the advance back in more quickly?
    Thanks
    Roy

  2. #2
    LT1 specialist steveo's Avatar
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    burst knock retard is there so when you stab the throttle really hard, there is some 'forced' knock retard added. the idea is, if we know there will probably be knock due to how hard the throttle is mashed, we can add some knock retard first. that way the knock never actually happens and the effect is less extreme.

    if you have tons of knock counts when you stab the throttle, that's not burst knock, it's real knock.

    in fact adding more burst knock may help account for the delay in your meth, as it effectively removes some timing advance on a throttle stab then adds it back in (which is exactly what it sounds like you're trying to accomplish)

    to make it recover more quickly from a knock event, just increase your knock retard recovery rate.

    honestly on a lot of builds, i've found it helpful to just disable knock retard entirely, and just rework the timing tables until things are conservative and safe. sometimes you spend so much time fighting a system that it's better to work around it. if your fuel is consistent and your tune is conservative, there should be no need to have active knock retard

  3. #3
    Fuel Injected!
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    What happens is when I stab the throttle hard as you suggested, it pulls a bunch of timing out, then it slowly adds it back in. My assumption was it was real knock, and it was happening because the meth hadnt kicked in yet, so my understanding of the terminology Burst knock was apparently wrong. Either way, when it kicks down from 3rd to 2nd and starts the pull at say 3500 RPM, it will slowly start to put advance back in, and it can take all the way until it is up to 5500 RPM before it puts it all back in. My knock retard recovery rate is set at 1, what sort of numbers are acceptable to put in this table?
    Last edited by Fastmax32168; 10-03-2021 at 10:58 PM.

  4. #4
    LT1 specialist steveo's Avatar
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    you should look at what happens in your log, do the knock counts increment a lot, or does it just give you a bunch of timing retard? if there are knock counts, then it's real knock, and not burst knock. you need to remove timing advance to fix that.

    you want to increase the recovery rate until it's fast enough for you. try increasing by 1 at a time (twice as fast). if you go too far, it will end up in a vicious cycle where it knocks, only removes timing for a moment, then knocks again.

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