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05-18-2015, 08:49 PM | #1 | |
Join Date: Mar 2015
Location: in a truck
Posts: 116
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Quote:
87, unless at high altitudes. 85 at high altitudes. Make sure the octane rating is (R+M)/2. Some places use different definitions of "octane rating." Many engines loose power and efficiency as octane ratings go up because the slower flame front propagation does not allow peak cylinder pressure early enough in the combustion stroke. Tdub (stock engine with rejet) lost power slightly over 88 octane, exponentially. Tdub2 (267cc EFI, 11.6:1 compression, timing advanced 4* with ping sensor and ignition retard to run 87 when necessary) gains power with up to 97 octane, then levels off. Pirate (276cc carbed, 12.7:1 compression) requires 93, and really likes 103. My son put 87 in Pirate, rode 1/4 mile, shut the bike off and pushed it home. It pinged so bad he thought he had blown the engine. To vary octane we started with 87 E0 and added toluene, a common octane booster and paint thinner.
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