Having some knock readings, need advice.
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This is a discussion on Having some knock readings, need advice. within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hello everyone, I am tuned on a COBB 91 octane shelf map, but can only use 90 octane because I ...

  1. #1
    Registered User Joshmath's Avatar
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    Having some knock readings, need advice.

    Hello everyone, I am tuned on a COBB 91 octane shelf map, but can only use 90 octane because I live in Alaska and that is all we have. I decided it would be interesting to log in a morning run with the engine warmed up on my way to work. What I found was a little bit of feedback knock that I have never had in my countless other tests, does this look scary or should I not worry about it? Getting it tuned other than a third party tune is not an option for me as i am 300+ miles away from a tuner. No dyno in Alaska.

    https://docs.google.com/spreadsheet/...XFhdkQ4Ny00OXc

    Lemme know what you guys think, thanks!

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    Registered User Heide264's Avatar
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    That's not in a good spot either - fairly high load and right before 4k.

    I'm not sure where to go from your situation though. I'd keep an eye on it in the future and note if it is repeatable. It could have been a 'false positive'.
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    Registered User Joshmath's Avatar
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    thanks heide I will take that into account, I will log again after work.

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    Registered User shadowpr's Avatar
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    If you want a pro tune, there are several tuners that do email tunes.

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    Lando Calrissian DemonWRX's Avatar
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    I had some similar knock, though my mods and tune are different. There are a few steps you can take....I did option 1 below, which fixed mine up nicely.

    Option 1
    First, colder plugs. Install, or have installed, some plugs that are one step colder.

    Second, get the cobb access tuner race software (free download from them, you just have to register for it). Then you can modify the map to make it slightly richer right around the knock area.

    Option 2
    get an e-mail tune
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    Master Baiter EJ257's Avatar
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    The knock is right after you peg the throttle. Try starting your pull around 2K (instead of 3K) and see if you still knock in those cells.

    Make this log a bit more specific (so you get better resolution). Log only the following:
    Load
    RPM
    DAM
    FBKC
    FLKC
    Ignition Timing
    Boost
    Throttle
    Last edited by EJ257; 08-14-2012 at 11:25 AM.
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    Registered User Joshmath's Avatar
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    hey demon any plugs you suggest? Thank you guys for the look, I will take that into account EJ, I am going to start pulling around 2k in third. not sure why I started at 3k ><

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    Lando Calrissian DemonWRX's Avatar
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    Yeah....

    NGK Iridium IX LFR7AIX 2309
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    Registered User Joshmath's Avatar
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    Amazon.com: 4 New NGK Iridium IX Spark Plug LFR7AIX # 2309: Automotive, seems like a good deal 4 pack for 30 bucks, those are the ones you were talking about right? And I need 4?

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    Lando Calrissian DemonWRX's Avatar
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    Yes, that is a good deal (brick and mortar store price is about $44)....yes those are the right ones, and yes you need 4.
    Stink-Eye Mob #39
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    Lando Calrissian DemonWRX's Avatar
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    Word of advice from personal experience, they are difficult to install due to location. From what I was told by my dealer (I paid to have them installed after 3 separate failed 1-2 hour attempts), you would need to unbolt the engine from the mounts and either shift it to one side, or tilt it so that you have room to get to the rear plug on each side.


    it is a good thing they are supposed to be good for 100K miles
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    Registered User Joshmath's Avatar
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    holy heck! what did the dealer cost?! And did you notice any differences with those spark plugs in? I'm just hoping this minor knock is just a small inconvenience and nothing to do with my 90 octane on a 91 tune. And dude, go Pirates.

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    Registered User Joshmath's Avatar
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    And does over boosting have to do with anything? I'm getting up to 18 psi and my tune says 16.8 psi trickling down to 14 psi at redline (7000)

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    Registered User Joshmath's Avatar
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    oh and devil. I do have the access tuner race software.

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    Lando Calrissian DemonWRX's Avatar
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    Quote Originally Posted by Joshmath View Post
    holy heck! what did the dealer cost?! And did you notice any differences with those spark plugs in? I'm just hoping this minor knock is just a small inconvenience and nothing to do with my 90 octane on a 91 tune. And dude, go Pirates.
    My knock issue was decreased by about 40-45% with the colder plugs, then eliminated by tweeking the fuel map. It was over a year ago, so I don't remember exact cost, but I think it was about $120....my dealer charges $90 an hour. A regular mechanic would likely be less.

    Quote Originally Posted by Joshmath View Post
    And does over boosting have to do with anything? I'm getting up to 18 psi and my tune says 16.8 psi trickling down to 14 psi at redline (7000)
    Which map are you on? Which version? (current versions are MTv 300)

    Stage1 91 is ~15psi peak boost pressure tapering down to ~13psi by the 7000 RPM redline, +/- 0.8psi.
    Stage2 91 is ~17.0psi tapering down to ~13.0psi by the 7000 RPM redline, +/- 0.8psi.

    Over boosting is not good, but if you are on the stage2 91 you are only over by 0.2 psi....which is not much.

    Out of curiosity, have you tried the ACN maps? I am throwing this out there for more input from other members, but if 91 octane is not available up there, would using an ACN 91 map be safer??? Don't use the ACN maps without someone who knows them chiming in.


    Quote Originally Posted by Joshmath View Post
    oh and devil. I do have the access tuner race software.
    Yes I do....though I had to get help at CF12 to figure out how to use it....we can walk you through it.
    Stink-Eye Mob #39
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