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Thread: ignition values in Tunecu

  1. #1
    apriliaforum Member laszlo__'s Avatar
    Join Date
    Sep 2005
    Szekesfehervar; HUNGARY

    ignition values in Tunecu

    Dear All,
    Hope a wise internal combustion expert can answer my question.
    Any of the tune maps let it be Futura or Caponord, shows lower and lower ignition advance values as the engine load increases.
    In my understanding as the engine load increases, more and more fuel injected into the combustion chamber and more fuel requires higher ignition advance to perfectly burn up all of the injected fuel in time. It means, the spark discharge must happen sooner before the TDC.

    Contrary Tunecu shows less and less ignition advance as the load increases. (Not the rpm !!)
    Can somebody give me explanation for this phenomena?
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    2013- APRILIA ETV1000
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  2. #2
    apriliaforum prov-nov Kennibear's Avatar
    Join Date
    Aug 2016
    Washington State USA
    Under partial load the mixture in the combustion chamber is not as easily lit. But under high loads (maximum volumetric fill) the mixture is just about ready to detonate/diesel anyway so the flame front moves away from the spark plugs pretty fast. Lower loads the flame front proppagates much slower so the ignition needs to be advanced. Ford's early stratified charge experimental engines used something like 60 degrees BTDC to light off.


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  3. #3
    apriliaforum expert brmbrm's Avatar
    Join Date
    Mar 2004
    North Wales
    1950's and 1960's bikes had an ignition retard lever to retard the ignition when under high load eg full throtle hill climbimg.
    To prevent pre-ignition/knocking.
    I assume this is a digital version of that.
    My name is Dave,
    bike's name is Black Betty.

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    Caponord - Douglas Dragonfly - 1942 Harley back again
    Pegaso - Matchless G3LS - BSA A7SS - 1942 Harley - Matchless G80/600cc - Matchless G3LS - BSA C15 - Velocette

  4. #4
    apriliaforum expert catfish's Avatar
    Join Date
    Jul 2003
    Morgan Territory, CA
    Low-density mixture (1/8 throttle) burns slow; needs more advance. High density (WFO!) burns fast, so needs less advance.

    Goal is always peak combustion pressure just after TDC.

    Catfish ...

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