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Thread: Timing higher than high octane chart

  1. #1
    Advanced Tuner
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    Timing higher than high octane chart

    So I've been driving this bone stock truck quite a bit lately and decided to revisit the tune to see how things are going. I'm getting KR around 0.64-0.72g airmass in the higher rpm, and in the log I'm seeing towards 20 degrees advance before the KR kicks in. However, in the tune it is only 17-18 commanded. I do not see any adders such as ECT or IAT in this area, and they actually remove timing. Any ideas where this is coming from? Log and tune posted. For this run, I disabled burst retard as well as knock learn, but no change in the logs other than no more burst knock (and still no KR where the burst knock was, in lower rpm areas). I also have a 2nd gear WOT in the log from a stop, at 2:49.111, of which there was no KR all the way up to 2900 rpm where I got off the throttle and let it upshift. Timing in the cal actually starts decreasing from there as you go up in rpm or airmass, yet the log shows it going higher.

    The fuel was dialed in with a wideband a couple of years ago and I haven't messed with it since. The wideband is semi-permanently mounted in my other truck at the moment. But as I was saying, I was just revisiting the tune since I am driving it much more lately, and cannot figure out where this additional advance is coming from. I filled up the past 2x with 93 octane, guessing the tank has about 92 in it now. It does not seem to affect the KR at the higher rpm/load, maybe erased some small amounts lower down.
    Last edited by NotSure; 09-30-2022 at 08:28 AM.

  2. #2
    Potential Tuner
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    Dec 2019
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    I had a similar issue and found out the power enrichment ad camshaft angle can each add timing. have a look at your spark table for PE.

  3. #3
    Tuning Addict 5FDP's Avatar
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    May 2012
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    Rogers, MN
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    The base fuel spark correction table can add timing based on how you have it setup.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  4. #4
    Advanced Tuner
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    Quote Originally Posted by 5FDP View Post
    The base fuel spark correction table can add timing based on how you have it setup.
    Ooohh, I looked at that chart and took the column headings as being Lambda, not EQ Ratio. Especially since the chart description says its purpose is to add spark during lean cruise, and it has bigger numbers at the higher EQ! I will adjust accordingly but the numbers in there seem to match up with what the logs say. Thank you!