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Thread: OEM LT4 Tune - Knock Normal?

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    OEM LT4 Tune - Knock Normal?

    I have a C7 Z06 with a LT4 with a AFE intake and Mamo Ported throttle body. I just bought the car and hooked up hptuners to log and mess around some. Just to note, the car was on 93 octane on the east coast and has only cycled through a half of tank of 91 thus far. Additionally, I've never messed around with a GenV ECU so may be logging the wrong PIDs. A couple questions:

    1) On the OEM tune I'm seeing a good bit of knock under acceleration, both hard and driving around town. The thing I find weird is that the car isn't pulling timing with the knock, it just continues on the same track. I know the GM cars sometimes knock a good bit from the factory, especially on 91, but is this normal? Or is it from the air mods and I should I start backing off the timing?
    2) Incoming ricer question: I can't seem to get the car to pop on decel. I've tried all my tricks from gen4 ecu and other platforms, and also followed the advice on here to modify the base min final spark tables, and tried dfco on and off, however it still does not pop on decel. Is there something I'm missing? It is on factory exhaust, but the automatic and ZR1 pop on factory exhaust, so I figure I have to be missing something.

    I've attached a log with knock on a quick 2nd gear pull and some knock in driving around town. Please note I live in AZ so it's hot as F out here.

    I also attached my tune file (which has dfco disabled and min final spark tables adjusted - I also just realized reviewing one more time that the long table I didn't adjust to -10 also, so maybe that's why? But it should still pop at 5-10 spark I'd think based on knowledge from other platforms).

    Thanks!
    Attached Files Attached Files

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    I did a much longer log yesterday and there is knock just everywhere. Pretty much anytime I accelerate. This is with the oem tune. (attached)

    I've pretty much decided to get a tune at this point as I don't like how it looks (and it's pulling a ton of timing), but any insight would be great on whether this is normal or not or being caused by the Ported Throttle Body and Intake. I don't see how 10+ degrees of knock at 9 degrees of timing is possible without hearing it or having major issues, so I figure some of it has to be phantom knock from the torque tables or something? But it was 112 degrees outside (Arizona) so maybe that is factoring into it, MAT and IAT seem hot but not excessive considering.

    Note: I tried reducing timing and also zero'd out the cylinder spark retard table (I read something about that on the forum) and neither removed it.

    c7z06_drcruise3_pops.hpl

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    Senior Tuner Ben Charles's Avatar
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    The thing is about this is its modded some on a factory tune and 91 doesn’t help!!

    Saying this... the factory calibration still fairly safe and the knock sensors are even predicting knock.
    All factory cars I see knock retard being pulled!
    It’s something the ECM is seeing, you certainly not hearing any I assume

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    Yeah I'm not hearing any audible knock.

    I just find it odd it's showing that much knock retard when these are mods people run on oem tunes all the time according to the forums. Leads me to believe it had to be showing knock retard stock, which you seem to see also.

    For me, I'm going to take it easy and throw on a couple more mods and then get it professionally tuned.

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    The aftermarket intake cause a change in Airmass calculations which shifts the spark lookup to a see a higher value. This is one of the reasons aftermarket intakes pick up power on the dyno. The stock intake and stock tune do actually show KR on crap gas so thats not abnormal, but it is likely exacerbated since the ECU is now trying to run an extra 1/2 to 1 degree of timing. 91 octane will show KR on these cars. Shell gas is crap and will show KR where good gas like Chevron, Mobil/Exxon and Sunoco won't. Not sure why Shell is KR prone but it is. I've seen it over and over again. Don't use shell.

    That said, the ECU has fail safes built in(stock tune) that will start to learn a Knock Factor and blend spark down between the Lo and Hi tables to avoid engine damage so I doubt you will have any issues. But for everything I just said, it's useless to throw parts on these cars and not tune for them. You pretty much end up with little to no gain without tuning.
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    Quote Originally Posted by TriPinTaZ View Post
    The aftermarket intake cause a change in Airmass calculations which shifts the spark lookup to a see a higher value. This is one of the reasons aftermarket intakes pick up power on the dyno. The stock intake and stock tune do actually show KR on crap gas so thats not abnormal, but it is likely exacerbated since the ECU is now trying to run an extra 1/2 to 1 degree of timing. 91 octane will show KR on these cars. Shell gas is crap and will show KR where good gas like Chevron, Mobil/Exxon and Sunoco won't. Not sure why Shell is KR prone but it is. I've seen it over and over again. Don't use shell.

    That said, the ECU has fail safes built in(stock tune) that will start to learn a Knock Factor and blend spark down between the Lo and Hi tables to avoid engine damage so I doubt you will have any issues. But for everything I just said, it's useless to throw parts on these cars and not tune for them. You pretty much end up with little to no gain without tuning.
    The only thing I don't understand is it doesn't appear the knock learn factor is working correctly. It seems to spike to 1.00 and then drop back to 0 very rapidly. Occasionally it works as intended and slowly climbs up or drops down but then it'll spike one way or the other again during a knock event. It's not protecting much if it jumps back to 0 10 seconds after a pull that had 10 degrees of knock.

    And I totally agree, that's why I have a HPTuners cable to be able to plug in and take a look, so I can monitor and get it tuned when needed. I know enough to be dangerous but the Gen5 is a lot more advanced than I'm used to so don't want to mess with it at the moment beyond little things.

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    Senior Tuner Higgs Boson's Avatar
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    did you buy it new or used and if used are you sure it wasn't previously tuned?

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    Quote Originally Posted by Higgs Boson View Post
    did you buy it new or used and if used are you sure it wasn't previously tuned?
    Used. Previous owner didn't say it was tuned. I compared against a 2019 stock z06 file and it was basically the same in most places minus some places which were minor and I think was just the different in the 2019. Pretty sure it's an oem map.

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    Quote Originally Posted by Creatre View Post
    The only thing I don't understand is it doesn't appear the knock learn factor is working correctly. It seems to spike to 1.00 and then drop back to 0 very rapidly. Occasionally it works as intended and slowly climbs up or drops down but then it'll spike one way or the other again during a knock event. It's not protecting much if it jumps back to 0 10 seconds after a pull that had 10 degrees of knock.

    And I totally agree, that's why I have a HPTuners cable to be able to plug in and take a look, so I can monitor and get it tuned when needed. I know enough to be dangerous but the Gen5 is a lot more advanced than I'm used to so don't want to mess with it at the moment beyond little things.


    Knock learn factor isn't applied at all loads from what I've seen. Also, try changing the logging frequency of the knock learn factor and see if it makes more sense. Some PID's like that lag behind the others at the stock settings.
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