OK, You are right. With no cat and after mkt exh its no prob tho'.

 

Octane ratings are diff in euro and america.

The octane rating shown in Canada and the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel.

 

My Dyna is happy with regular, but the RKC wants mid-hi grade, especially in hot weather.

 

Don't believe the octane levels it's all the same 87 or 93 my bike never pings , like usual your government is robbing you !! lol

 

I thought the newer bikes required premium gas? Mine had a sticker on it when I baught it that said premium only. I know the engine will still run on 87 and such but why not use what they ask for when its going to cost you an extra dollar maybe two.

 

I always use 93 because, like mentioned, its only a buck or so more and that's what's suggested in the manual. However, I'm not sure why. Isn't the octane rating of gasoline merely a number associated with the potential for pre-ignition? Meaning, a high compression, high revving engine's fuel/air mixture to spontaneously combust on the compression stroke due to heat generated by pressure before the spark plug fires... and higher octane will prevent this condition. Never really thought of a Harley engine as high compression and certainly not high revving. Am I off in my belief of what octane ratings really mean?




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The highest octane available at whatever gas station that I'm near when I need gas. I like the 93 octane.

 

No you're right about what higher octane does. The reason is that these are air-cooled engines and can end up running a lot hotter than liquid cooled engines. Also, and I'm not sure what the timing is on our engines, but the further you advance the spark timing, the more likely you are to have detonation. Just as a comparison, aircraft piston engines are even lower compression than ours (like 8.7:1) and they require 100 octane LEADED(lead also helps prevent detonation) because they are also air-cooled and run a pretty advanced spark.

 

It is also worth noting that the way octane prevents detonation is that is causes the fuel mixture to burn more slowly. So if you use higher octane than called for on a certain engine, you are actually going to hurt performance. Also, "premium" is not cleaner or better than regular - it just has higher percentage of octane.

 

Ahhhh.... air cooled engines running hotter. More ambient heat to begin with just adds to the natural heat generated during the compression stroke by all those little fuel/air molecules squeezing together at high speed increasing the potential for pre-ignition. Hadn't thought of that. You are wise grasshopper.




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