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Thread: E39 lfx kr

  1. #1
    Lifetime Member Rhino79's Avatar
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    Default E39 lfx kr

    Anyone noticing a rediculous amount of KR at wot with premium fuel. I have reduced the timing a bit and still seems to be showing crfazy knock. Ive drained the tank and refilled and still the same. Is this normal and are the kr settings overly sensative in this ECM?
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    Gwatney Performance Innovation
    Jacksonville, AR 501-982-2102

  2. #2
    Joe (Moderator) joecar's Avatar
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    Post log files.

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    Lifetime Member GMPX's Avatar
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    Not only seen it, you can hear them knocking sometimes , well, that is on the LFW I must admit, but isn't the LFX just a bigger version of that engine?
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    Lifetime Member Rhino79's Avatar
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    10:1 compression (stock is 11.6:1), stock engine with forged pistons and twin 62s on 93 octane, zl1 pump and running 50/50 water meth.
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    Gwatney Performance Innovation
    Jacksonville, AR 501-982-2102

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    Lifetime Member GMPX's Avatar
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    Ahhh, ok, that's a little different then. LFX is E85 capable right?
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  6. #6
    Lifetime Member Rhino79's Avatar
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    I have enough fuel system for it yes. I am also going to try another spark plug. I have found the coldest I can run is an LTR7ix11
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    Gwatney Performance Innovation
    Jacksonville, AR 501-982-2102

  7. #7
    Lifetime Member swingtan's Avatar
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    If it's anything like the E39 SIDI motor, then I think the knock is a "design feature". The only way I could effectively reduce it in mine was to run a 17% ethanol blend (as a test I added about 15L of E85 fuel to the tank). This made a significant difference to power and the knock levels.

    Generally though, I work on the usual fuel and spark tables to tune out the KR. I actually increase the sensitivity settings to try and reduce the audible knock as well.

    If you think you are getting false KR, then look into "Knock Balance Rates" {B1940} in my OS. Any positive value in here has the tendency of adding KR even when nothing is detected. I should do some more work on that table to see if it can be effectively used when tuning, or if it's just a stock OS fail safe for the all encompassing tune.

    Simon.

  8. #8
    Lifetime Member Rhino79's Avatar
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    It is an sidi motor. So for tomorrow I'm gonna swap/read plugs. Go colder if needed. I'll check those tables Simon. I actually bumped the noise threshold up in hopes I would see a change in kr reported but no. I'd like to give the owner an 93 and e 85 tune, but I hate to have to detune it son much if it"may" be false knock.
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    Gwatney Performance Innovation
    Jacksonville, AR 501-982-2102

  9. #9
    Lifetime Member Rhino79's Avatar
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    Another reason for me to believe its false is that the pistons are now 2618 forged and run much more skirt clearance than stock. Nearly .003" more than stock I do believe.
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    Gwatney Performance Innovation
    Jacksonville, AR 501-982-2102

  10. #10
    Joe (Moderator) joecar's Avatar
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    If you can, use a listening device (e.g. Chassis Ear) to listen to the block while running on the dyno, real knock will be apparent and distinct from other mechanical noise.

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