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Thread: Knock Sensor Level on Trucks?

  1. #21
    Senior Tuner 10_SS's Avatar
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    Mine goes away when it's cold out... only this bad when it's warm/hot out so i'd say it's real. Whoever thinks it's false just pull 10 degrees of timing in this area and see if it is reduced. This will only work if you disable Knock Learn though, or monitor Knock learn when you pull the timing, see if it ends up at a much lower value. It will take awhile for that table to lower.
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  2. #22
    Tuning Addict WS6FirebirdTA00's Avatar
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    Sorry cam retard not spark retard.
    2000 WS6 M6 (motorless)
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  3. #23
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    This issue had me freaked out a little because on my 14 Sierra L83 I upped timing and a little and DD tables etc and it felt really good to me but I was only checking for KR on wot. Well I did another log after upping the predicted pressure drop in the airflow table and i noticed a ton of knock at cruising speeds, up to 8*. I changed tune back to previous and logged, still had cruising knock 35-40 % throttle and 85kpa doing 55mph, 3-5*. So i went back to stock tune and on completely stock it STILL had up to 4* KR. I hate to ignore since its so high in the map range, but maybe i have a misconception of the MAP because i don't think there is much load at cruising but the MAP tells me the cylinders are filling with a good amount of aircharge…? I never hear audible knock. Since it does this on a completely stock setting I don't think i really have a problem...
    Last edited by MrFixIt86; 03-11-2020 at 05:29 AM.
    14 GMC sierra 5.3

  4. #24
    Advanced Tuner mbray01's Avatar
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    again as stated, knock sensors are very sensitive.
    Michael Bray
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  5. #25
    Advanced Tuner Obsolete489's Avatar
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    I desensitized the knock sensors some in the low rpms areas, this reduced kr but it's still present. What's annoying is when it does throw a bunch of kr it knocks me into single digit timing, even on e85, which makes the truck fall on its face. As of late I've been playing with SOI to see if I can reduce the low rpms kr.

    Just to be clear, this is at low rpm (1400-1600), higher rpm high load I never see KR.
    2000 K2500 - 489 CI Vortec w/ comp XE270 cam - rear mount turbo in progress/testing
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    2014 Silverado 1500 w/ L83

  6. #26
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    So nothing to worry about it sounds like. Thanks Bray and Obsolete for a little piece of mind. Sorry for redundancy
    14 GMC sierra 5.3

  7. #27
    Advanced Tuner Obsolete489's Avatar
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    It really doesn't seem to be an issue, but I'd still like to get rid of it if I can. If I figure out anything with SOI I'll post back.
    2000 K2500 - 489 CI Vortec w/ comp XE270 cam - rear mount turbo in progress/testing
    1972 M35a2
    2014 Silverado 1500 w/ L83

  8. #28
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    I've got rid of all knock while cruising and light throttle areas by adjusting SOI table. There is a good thread in the forum here about the SOI tables. Ben suggested setting up a histogram of KR compared to the CYL. airmass and RPM. I copied column and rows from the SOI table and inserted the knock parameter and where ever I seen knock I upped the degrees of SOI 5 or so and did a little smoothing in the area there was knock and that made a world of difference. As stated theres no harm to be done on such low cylinder pressures at cruising but it was just a piece of mind for me, and sense of accomplishment lol.
    14 GMC sierra 5.3

  9. #29
    Advanced Tuner Obsolete489's Avatar
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    This seems to be working for me as well. I haven't gotten everything to go away yet (1500-1600 rpm is being a bitch), but I'm seeing improvements. I'm taking increases slow, a few percent at a time.
    2000 K2500 - 489 CI Vortec w/ comp XE270 cam - rear mount turbo in progress/testing
    1972 M35a2
    2014 Silverado 1500 w/ L83

  10. #30
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    I'm anywhere from 310 to 325 degrees in the 14-1600 rpm range. I only find KR now when i'm in decal and get back into throttle to sustain speed. I'm assuming lean from being in DFCO. I have conservative timing right now because I haven't messed with factory fuel tune. Wideband going in tomorrow so I can perfect the fueling then get spark dialed in. Just been playing around WITHOUT wideband so far. Good seat of the pants feel so far but I know I got more left to gain with stock tune demanding like .82 or .85 eq ratio, way rich for N/A. That's just what commanded says, I have no real idea what is actually spitting out the exhaust.
    Last edited by MrFixIt86; 03-19-2020 at 10:01 PM.
    14 GMC sierra 5.3

  11. #31
    Advanced Tuner Obsolete489's Avatar
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    Quote Originally Posted by MrFixIt86 View Post
    I'm anywhere from 310 to 325 degrees in the 14-1600 rpm range. I only find KR now when i'm in decal and get back into throttle to sustain speed. I'm assuming lean from being in DFCO. I have conservative timing right now because I haven't messed with factory fuel tune. Wideband going in tomorrow so I can perfect the fueling then get spark dialed in. Just been playing around WITHOUT wideband so far. Good seat of the pants feel so far but I know I got more left to gain with stock tune demanding like .82 or .85 eq ratio, way rich for N/A. That's just what commanded says, I have no real idea what is actually spitting out the exhaust.
    What cyl airmass are you commanding that at? It is usually .5-.6 that I'm seeing issues. Perhaps i need to jump more in those areas? Or maybe I am just letting this thing hold its gear too long and need to downshift to avoid .6 cyl airmass at low rpm?
    2000 K2500 - 489 CI Vortec w/ comp XE270 cam - rear mount turbo in progress/testing
    1972 M35a2
    2014 Silverado 1500 w/ L83

  12. #32
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    300* at .6 and 1500 rpm. 325* at 1600 and .50. Probably should be smoothed but I has having issues at the .50 and .48 air mass at 1600 rpm.
    14 GMC sierra 5.3

  13. #33
    Advanced Tuner Obsolete489's Avatar
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    I'll try running in that area and see what happens, and report back. Hopefully this takes care of the 1600 rpm range, down in the 1400-1500 range I pretty well eliminated kr and it really made a difference in how the truck feels down there.
    2000 K2500 - 489 CI Vortec w/ comp XE270 cam - rear mount turbo in progress/testing
    1972 M35a2
    2014 Silverado 1500 w/ L83

  14. #34
    Tuning Addict WS6FirebirdTA00's Avatar
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    What were your stock tables set to? Also what timing?

    Here is what I have at 1600 and the respective airmass:

    0.48 0.52 0.56 0.56 0.60 0.64 0.68 airmass
    285 290 275 275 260 255 250 SOI
    17.5 13.5 10.0 8.5 6.5 5.5 4.5 HO timing (now)
    18.0 15.0 12.0 9.0 7.0 4.0 2.0 HO timing (stock)

    That is where I see most KR.

    Do you have a link to the post you were reading?
    2000 WS6 M6 (motorless)
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  15. #35
    Advanced Tuner Obsolete489's Avatar
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    Quote Originally Posted by WS6FirebirdTA00 View Post
    What were your stock tables set to? Also what timing?

    Here is what I have at 1600 and the respective airmass:

    0.48 0.52 0.56 0.56 0.60 0.64 0.68 airmass
    285 290 275 275 260 255 250 SOI
    17.5 13.5 10.0 8.5 6.5 5.5 4.5 HO timing (now)
    18.0 15.0 12.0 9.0 7.0 4.0 2.0 HO timing (stock)

    That is where I see most KR.

    Do you have a link to the post you were reading?
    Here is what I'm at currently. Still testing the 1600 rpm range, not as often i see high airmass there. It'll still kick some kr occasionally but it is much improved. Please not I've only been testing on E85, so i'll need to go see what 91 octane does sometime.
    timing current.PNGSOI Current.PNG
    2000 K2500 - 489 CI Vortec w/ comp XE270 cam - rear mount turbo in progress/testing
    1972 M35a2
    2014 Silverado 1500 w/ L83

  16. #36
    Tuning Addict WS6FirebirdTA00's Avatar
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    Thanks. I am running 93, FYI.
    2000 WS6 M6 (motorless)
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  17. #37
    am i correct in that the knock sensor multiplier tables for each cylinder on the e92 the smaller the number the more sensitive the sensors will become? i find it hard to believe that i cant run stock timing below 3000 rpm on my l86 on 93 octane.

  18. #38
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    Quote Originally Posted by tjd1991 View Post
    am i correct in that the knock sensor multiplier tables for each cylinder on the e92 the smaller the number the more sensitive the sensors will become? i find it hard to believe that i cant run stock timing below 3000 rpm on my l86 on 93 octane.
    Yes, the smaller the more sensitive. I typically set them to 4.0 or 5.0 and then set the decay rate to 0.6. This seems to be a safe area for 93 octane street car. You can get more aggressive on the decay rate but that is up to you and how safe you want to keep the car. I've had it up to 3.0 before on the decay rate without any issues on an NA car with full headers and exhaust and 93 octane. I just don't feel comfortable with anything past 1.0 on decay unless its a track tune and you're monitoring everything on the runs.
    I've tuned a few things...

  19. #39
    I am going to start small here and leave decay alone for now and try some small SOI timing changes as well.

  20. #40
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    I'm up to 320* SOI in those areas at 16-1800rpm you speak of and .52 airmass and up. I get up to 330 at high rpms in the 60+ airmass. I had the exact areas knock. From my research as long as your pulse widths are not being cut short you want to inject as late as possible. I'm around 4.5ms injector PW in high rpm areas. Also read 338 from one source and 350* from another as being the possible max. I'd stick to the 338 if your pushing it. I don't go over 332 on my SOI table. I am at 28* spark advance with no knock, stock set up, also no knock down low cruising.
    14 GMC sierra 5.3