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Thread: Timing, Spark Advance, Electronic Distributor Advance and Knock Counts

  1. #1
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    Timing, Spark Advance, Electronic Distributor Advance and Knock Counts

    I've been searching and reading and I've found bits of data here and there but it's a jungle of info out there with few maps or signs to navigate, so here are some questions in one thread.

    Base Timing - If I decide to set my base distributor timing to say 8 or 10 BTDC, where do I change that in the bin? I think it should be in "main spark bias" in scalars. The tip listed in the xdf I'm using says "Tips: Compensates for the spark advance added by mechanical means. This should be set to the same value that distributor is set to." But what about Main Spark Bias? What does it do and does it need changed?

    Electronic Advance - What is the maximum advancement the distributor can add? I saw this in a thread but I can't find it again; I think I read that it was 42. Also, when logging I see my advance occasionally goes up into the low 40s and is red on the gauges. My highest value on the Main Spark Table is 36 so the PCM is adding 7 or more for some reason. What values add to the timing? And if the timing does in fact need to be more advanced than the electronic distributor maximum, I need to set the base timing to have some advance, right?

    Knock Counts - What number is high here? Is 100 high? How can you tell when knock is being recorded vs historical knock count? I have searched about this but haven't found definitive answers here.

  2. #2
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    Some of these questions I have a vague idea of, but I'm also trying to phrase things and set up thread title so that the next person searching this can find answers more easily. There is a vast wealth of knowledge in this and other related forums, but it isn't indexed very well; thread titles are random and terms you would search are used repeatedly in all sorts of topics. Once I start to figure out a little more about what I'm doing here I would like to give some time to help organize things and maybe make or extend some FAQs if that is something that you guys would be interested in seeing happen.

  3. #3
    Fuel Injected!
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    Base timing value is set here:

  4. #4
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    If that is set, do you need to make any other adjustments? Does the PCM then subtract that from your SA table values?

    Say if in a cell you had a setting of 30. Then you set base timing to be 10. Does the computer subtract the 10 and advance the distributor to 20? This is what I would assume but I don't want to be assuming anything at this point.

  5. #5
    Fuel Injected! mmigacz's Avatar
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    (10 initial) + (30 commanded from table) - (10 from initial timing scaler) = 30 degrees actual advance seen at the engine.
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