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    Race fuel?

    I've never heard of anyone *needing* to run race fuel in a modded Hawk, but X was asking about this last night, since he's been having FI issues with his fancypants gixxer. He was wondering if I need octane booster or if it even makes a difference on a bike with higher compression. We're currently both running 93 octane pump gas.

    Neither one of us has any interest in paying $10 a gallon if we don't have to.

    We both found it a little amusing that me and my 20 year old bike ran all day long without issue, and he was chasing down problems on his high-tech '05 bike the whole weekend, and his issues still haven't been solved.

    (Watch me blow up my motor this weekend at Grattan for saying that.)
    '88 Hawk - Street '89 Hawk - Track '67 Fiat 500 - Luigi follow only the Ferraris

    #2
    Sock,
    from what I understand you really only need to use race fuel if you have hopped up your motor.
    More compression equals more likely detonation, higher octane fuels simply have a higher knock rating.
    Only thing is that some of the race fuels are blended to actually give better performance and may contain extra oxygen.
    Standard petrols (especially here in US) are blended with all sorts of shit to help with weather changes, stability and whatever enviro-crap (think ethanol etc) the politicians decide will make you lot{1} vote for them come next election!!

    Marc

    {1} Expat Brit so couldnt have voted Bush out, nor Obama/Clinton in!!!!

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      #3
      you're running 93 just fine now, so you have no need for higher octane.
      you might even go slower with it. lol.


      the higher the octane number, the more its resistance to combust....
      this sounds odd at first if you never thought about it, but it works like this:

      if the fuel combusts very easily.. it might ignite early or spontaneously while its being highly compressed in a hot cyl.....
      so you up the octane.. and it doesnt ignite as easily (or as fast) but it allows you to have higher compression...

      for a rule of thumb, you actually want to run the LOWEST octane you can with the motor that doesnt cause detonation... this allows a quicker combustion... meaning higher cyl pressure.. and more power.




      obviously thats a very small overview.. but thats it in a 45second nutshell.. lol.

      Comment


        #4
        Monkeygirl-

        "X" does not need high octane fuel in his bike. Keep in mind that a lot of high-zoot $$$ race fuels being used in professional racing are actually fairly LOW octane. Modern combustion chambers are very efficient and resist detonation well.

        OTOH you probably ought to run at least ~93 in your Hawk, since it is built up a bit. Built Hawks can ping a little if the timing is not sorted out. Since we don't know exactly what you have and how it's tuned, better to be a little on the safe side.

        FWIW my Hawk runs best on VP U4, which as I recall has motor octane number of ~92. I can get away with this octane and stratospheric compression ratios because the timing is well-sorted.

        Hord
        J.D. Hord
        Keeper of Engine Nomenclature, 9th Order

        Comment


          #5
          coolski - thanks for all the info.

          It makes it easier if we can both run the same gas, so that we don't have to have separate fuel containers, especially since we're short on room in the trailer.

          His bike is an '05 gixxer 600 that was built by Millenium/KWS Suzuki for one of their riders. We don't know exactly what she's got, but she's definitely had some work done. Someone at the track last week said something about being careful and needing to run race gas (here's where I forget details of what he was talking about and why). Anyway... he was getting a few good laps and then the bike would start coughing and the FI light came on.
          '88 Hawk - Street '89 Hawk - Track '67 Fiat 500 - Luigi follow only the Ferraris

          Comment


            #6
            You'll have to see what the service code is on the FI light, probably a crank or cam sensor going bad, something like that. The bike has no idea what octane it is running on so it can't be the fuel causing it. Even with a built engine he should be safe on 93-94 octane.
            J.D. Hord
            Keeper of Engine Nomenclature, 9th Order

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