mrmako777 Posted February 16, 2009 Report Share Posted February 16, 2009 I'm surprised it says 86 octane with a compression ratio of 12.0:1. High tech aluminum engines with high compression can run lower octane than what would traditionally be guessed at. There was an old magazine article that showed dyno tests on some high octane/compression bikes that actually produced more horsepower/torque on gasoline that was less than the factory recommended octane. Nobody knew why the engine would do that.yeah it sounds weird man. my 600 is pushin 12.5:1 and the manual says to run 87. not sure with such high compression why it runs lower octane. the 750 runs 12.8:1 and calls for 91. does .3 really make that big a difference? Quote Link to comment Share on other sites More sharing options...
wolfman Posted February 16, 2009 Report Share Posted February 16, 2009 yeah it sounds weird man. my 600 is pushin 12.5:1 and the manual says to run 87. not sure with such high compression why it runs lower octane. the 750 runs 12.8:1 and calls for 91. does .3 really make that big a difference?Nope, other factors are in play such as ignition timing. For example: my old jeep was ~11.0/11.5:1 and absolutely had to have 93. Quote Link to comment Share on other sites More sharing options...
fueljunkie1 Posted February 22, 2009 Report Share Posted February 22, 2009 OK here I'll try to break this down for you too. The closest correct answer I read here was the guy explaining the RON-MON thing. "Octane" is the word used to describe the relationship of Octane and Iso-Heptane in the fuel. ALL combustibles have a "critical pressure" under which they will self-ignite. Ever seen them drive a telephone pole in the ground? That's diesel full being squeezed to it's critical pressure and when it ignites the expanding gases lift the weight , exhausts, refuels, repeats.Camshaft profiles are how you can make a high compression engine cope with the lower rated fuels. That one gets REAL complicated, so just trust me there. The goal is to get the fuel as close as possible to critical without ignitiing it. That's where the whole carbon thing comes in with hot-spots etc.Endgame...there is no advantage to running higher octane than the engine is rated for. On many of the newer computer controlled systems it will actually rob you of power because the higher octane is harder to ignite and the computer starts playing with timing. The heat difference in BTU's for what we're doing is really intangible. Hope that helped...my fingers are tired! Quote Link to comment Share on other sites More sharing options...
NinjaNick Posted February 22, 2009 Report Share Posted February 22, 2009 I use what my sticker says on the tank. After I purchase the bike and see it, I then peel the sticker off and always fill up with premium like it stated. Quote Link to comment Share on other sites More sharing options...
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