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Old 01-06-2011, 09:19 PM
Sideshowbob's Avatar
Sideshowbob Sideshowbob is offline
Motorized Bicycle Senior Member
Join Date: Dec 2010
Location: Salem OR
Posts: 64
Default Re: id like to set something straight

My bike is a land yacht and I weigh 190, so when I am cuzing I am genreally from 3/4 to full throttle. I is correct to say that higher octane gas is less volitile and has better antiknock (predetonation) properties. Remember these little motors are very primative and in most instances low octane gas is fine and burns more eisily. But lubrication is key in 2 cycle motors and lube is required for valve guides in 4 cycle one. I don't think it really makes a hill of beans difference in speed. But higher octane is less likely to predetonate in higher compression engines. A fuel with a higher octane rating can be run at a higher compression ratio without causing detonation. Compression is directly related to power and to thermodynamic efficiency, so engines that require higher octane usually deliver more motive power and do more work for a given BTU or calorie of fuel. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber. When the throttle is partially open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to atmospheric pressure, or higher. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.
I do think in high compresion full throttle situations it will provide more lubrication and less predetonation (knock). I think I run high octane cuz I'm at full throttle often. But it sure ain't giving anyone more power. For more power try good bearings, port, polish, and BALANCE crank and piston will make the most difference. But a boost bottle could increase fuel efficiency just a bit. Just how much hydrocarob and O2 can you ram in there thats what counts for power. sorry for babbling on.
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