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Thread: Knock, Knock. Who's There? PLease Help

  1. #1
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    Knock, Knock. Who's There? PLease Help

    2008 Colorado 5.3L swap
    10.2-10.3:1 CR
    78/75 Turbo
    Intercooled
    No Meth
    91oct

    Cant seem to get a clean WOT pull without getting knock at some point. I'm only running 7ish lbs. I run 91 but have tried 100 with no change. 95% cetain exhaust is not hitting. Burst has been disabled, no change. I'm at 9 degs on the high end. I've had it down to lower and still get knock randomly.

    Attached Log and Tune are in MAF OL. I get similar knock results in VVE OL as well. Please review. Any input/suggestions would be greatly appreciated
    Attached Files Attached Files
    Isley

    2008 Colorado RCSB 5.3L Swap
    4.8 Flat tops, SS2, 3200 stall
    78/75 On3
    Knock, Knock

  2. #2
    Tuning Addict 5FDP's Avatar
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    Does it get better/worse or stay the same if you command say 10.8-11.0 instead of what you are now?

    I'm sure you are just working with the timing and that's why the high/low timing are the same.

    I'd probably desensitize the knock sensors just a little bit, they can be overly protective sometimes.
    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.

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    IAT sensor is in the MAF I assume in the cooler pipe?

    probably find its hotter in the manifold then the sensor is seeing and it has no compensation for IAT retard.

    try aiming for 11.0 AFR and be more aggressive ripping timing out on the ramp up to boost. the transition through the airmass axis on the spark table is important. pump fuel and decent comp will make it unstable and susceptible to knock during spool up.

  4. #4
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    Quote Originally Posted by 5FDP View Post
    Does it get better/worse or stay the same if you command say 10.8-11.0 instead of what you are now?

    I'm sure you are just working with the timing and that's why the high/low timing are the same.

    I'd probably desensitize the knock sensors just a little bit, they can be overly protective sometimes.
    I have it at 11.6ish in PE, I havent tried 11ish but I'll try that this weekend. Yeah, I left spark tables same but will reduce the low table down the road. I've gone back and forth with the idea of desensitizing the sensors but will probably do it if I confirm its false. Thank you for you suggestions.

    Quote Originally Posted by lukearmstrong1990 View Post
    IAT sensor is in the MAF I assume in the cooler pipe?

    probably find its hotter in the manifold then the sensor is seeing and it has no compensation for IAT retard.

    try aiming for 11.0 AFR and be more aggressive ripping timing out on the ramp up to boost. the transition through the airmass axis on the spark table is important. pump fuel and decent comp will make it unstable and susceptible to knock during spool up.
    You are correct, IAT is on maf in cooler pipe, now that you mention that, I have read about the inaccuracy of IAT in pipe vs mani. Thank you for pointing that out as well as suggesting the spark table and afr adjustments. I'll try it out this weekend.
    Isley

    2008 Colorado RCSB 5.3L Swap
    4.8 Flat tops, SS2, 3200 stall
    78/75 On3
    Knock, Knock

  5. #5
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    it may be worth getting onto a dyno with some knock ears and listening to the engine yourself as opposed to reading calibrated frequency data that doesn't directly relate.

    screamer pipes can upset knock sensors, as can pipes/manifolds vibrating against the chassis or engine.

    a poor plug lead or coil slightly breaking down under load will also cause knock.

    incorrect plugs for the application can also cause knock.

    too little timing on pump fuel with a rich AFR can also cause knock.

    too lean and too much timing will cause knock

    high inlet air temps at the manifold can cause knock also.

    the knock logged at 15.37.384 of your log shows 142KPA MAP 10 degrees timing and 11.60 AFR. given your barometric pressure shows 105KPA that means you're only seeing 37KPA boost or just over 5psi. even with 10.2:1 SCR that should take more than 10 degrees. you need to establish if the knock is real and if its caused by one or multiple of the above list items.

    knock can be caused by mechanical faults, its not always the tune. I would assume that on 5psi that engine at 10.2:1 comp would still happily take 15 degrees without knock.

  6. #6
    Advanced Tuner ttz06vette's Avatar
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    Quote Originally Posted by lukearmstrong1990 View Post
    it may be worth getting onto a dyno with some knock ears and listening to the engine yourself as opposed to reading calibrated frequency data that doesn't directly relate.

    screamer pipes can upset knock sensors, as can pipes/manifolds vibrating against the chassis or engine.

    a poor plug lead or coil slightly breaking down under load will also cause knock.

    incorrect plugs for the application can also cause knock.

    too little timing on pump fuel with a rich AFR can also cause knock.

    too lean and too much timing will cause knock

    high inlet air temps at the manifold can cause knock also.

    the knock logged at 15.37.384 of your log shows 142KPA MAP 10 degrees timing and 11.60 AFR. given your barometric pressure shows 105KPA that means you're only seeing 37KPA boost or just over 5psi. even with 10.2:1 SCR that should take more than 10 degrees. you need to establish if the knock is real and if its caused by one or multiple of the above list items.

    knock can be caused by mechanical faults, its not always the tune. I would assume that on 5psi that engine at 10.2:1 comp would still happily take 15 degrees without knock.
    That’s an interesting one. I started getting about 8* of timing pulled at around 3800-4800 rpm with AFR’s at about 10.5 under boost(12psi). This is while spraying meth. Been trying to troubleshoot by desensitizing sensors especially in cyl 8 where the most is occurring. Have checked exhaust to chassis and plugs. Maybe I should go the other way. Current total timing in this range is about 16 ramping down to 12.

  7. #7
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    Quote Originally Posted by lukearmstrong1990 View Post
    it may be worth getting onto a dyno with some knock ears and listening to the engine yourself as opposed to reading calibrated frequency data that doesn't directly relate.

    screamer pipes can upset knock sensors, as can pipes/manifolds vibrating against the chassis or engine.

    a poor plug lead or coil slightly breaking down under load will also cause knock.

    incorrect plugs for the application can also cause knock.

    too little timing on pump fuel with a rich AFR can also cause knock.

    too lean and too much timing will cause knock

    high inlet air temps at the manifold can cause knock also.

    the knock logged at 15.37.384 of your log shows 142KPA MAP 10 degrees timing and 11.60 AFR. given your barometric pressure shows 105KPA that means you're only seeing 37KPA boost or just over 5psi. even with 10.2:1 SCR that should take more than 10 degrees. you need to establish if the knock is real and if its caused by one or multiple of the above list items.

    knock can be caused by mechanical faults, its not always the tune. I would assume that on 5psi that engine at 10.2:1 comp would still happily take 15 degrees without knock.
    Well, Sorry for the late response. I actually tried 10.5-11 AFR a few weeks back and still no improvement. I;ll do a pull and get knock right off the back, and then a a minute later do a clean pull. This is getting frustrating.
    Isley

    2008 Colorado RCSB 5.3L Swap
    4.8 Flat tops, SS2, 3200 stall
    78/75 On3
    Knock, Knock