Pre-Ignition/Detonation Problem Maybe?

Discussion in 'Touring Models' started by dolce, Sep 24, 2012.

  1. dolce

    dolce Member

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    I have a 2011 FLHTK that I've had since February this year (bought new). Have about 5000 miles on it and have made only one performance/mechanical modification and that is a set of V&H slip on pipes. I did not have the ECU remapped when I put them on with advice from a technician. Bike has ran great with only a little decel pop from time to time, nothing over the top.

    Recently (2-3 times) when I've been in the middle of a relatively long ride (200-300 miles) and just after having been stopped in traffic for a period of time allowing the engine to get heated up pretty good I'll hear what sounds like engine knock (pre-ignition/detonation - not sure which). Could it be that the heads have gotten so hot that the fuel air mixture is igniting before it is supposed to? if that is the case, would an ECU software update along with intake make it run cooler?

    Thanks for the assist...
     
  2. Jack Klarich

    Jack Klarich Expert Member

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    Detonation and Pre-Ignition This will explain the differences , detonation is the engine destroyer hot spots across the tops of the pistons keeps burning= holes in pistons and shock to the rods and bearings
     
  3. Hoople

    Hoople Account Removed

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    You mean after being stopped in traffic and then you take off, you hear this noise. Or is the noise present while your sitting at the light.

    Do you have your the heat management software enabled? I use it as an indicator of engine temperature. It tells me if I am in the danger zone..

    "For a period of time" can mean anything. On these late model 96 & 103's, after the engine is fully heat soaked, you can't sit still for more than 2-3 minutes on a warm day without going above 300* on head temp.
     
  4. dolce

    dolce Member

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    It's not while sitting still. I had ridden from Knoxville TN through Boone NC and got caught at most of the red lights in town. On the other side of Boone at a constant speed and RPM of ~2500 (sixth gear). Under slight load of acceleration the detonation would occur. Stopped after 4-5 miles never happened again.

    I had the engine temp management control off initially but turned it on after the 2nd or 3rd light. It was hot enough for the front cylinder to shut off as designed.
     
  5. ironmark

    ironmark Junior Member

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    I just put fairing lowers on my bike and the engine does run hotter because I am getting spark knock now when I never had spark knock before. I am kind of wondering what I can do to eliminate this issue as well.
     
  6. Hoople

    Hoople Account Removed

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    The document Jack posted has good info in it. For starters I would fatten up the mixture. The spark advance map on these bikes during part throttle is pretty aggressive. Combine some overheating along with spark advance numbers like these, and it shouldn't be that big of a surprise.
    Harley does it to get the gas mileage figures up. It also helps with emissions. They count on the ion-sense knock retard feature to keep it contained and under control. Sometimes you just can't have both.
     

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  7. dolt

    dolt Senior Member Contributor

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    Remove the cat, add hi-flow air filter and good fuel management system like TTS Mastertune, get a good tune and both you and the bike will be happy.:bigsmiley12:
     
  8. Rod Stewart

    Rod Stewart Active Member

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    This may be a moot point, but if you are not running 91 octane gas, maybe try a tankful and see what happens.
    As your engine accumulates miles you get a small carbon buildup on the pistons and inside the combustion chambers. This has the effect of reducing the squish volume a little, which increases the effective compression ratio.
    This may be why you are noticing detonation now and not before.
    You may be just on the fringe of detonation when she is hot, especially if you are running less than 91 octane.

    Rod
     
  9. dolt

    dolt Senior Member Contributor

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    There will be very little carbon build up at 5000 miles; certainly not enough to change squish. The OEM head gasket is .045" and the pistons in the later engines are typically down in the hole. There is plenty of room for cabon builid up before it will change compression.
     
  10. dolce

    dolce Member

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    Thanks, I never run anything less than 91. Usually it's 93 but never less than 91.