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Honda MX & Off-Road Dirt Bikes
Crf250 Fuel
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[QUOTE="Rich Rohrich, post: 839731, member: 16241"] The octane rating has nothing to do with the laminar flame speed of the fuel, and running high octane fuel [b]WILL NOT REDUCE POWER[/b]. The hydrogen/carbon bonding of the fuel's components will determine how easily and quickly the fuel can be reacted and it's ultimate heat release. The fastest burning hydrocarbon based fuels you'll find will be the 118 octane Pro Stock fuels. You can have fast burning high octane fuels as well as slow burning high octane fuels but the difference between the two is negligible and will NEVER be noticed by a rider. Once you meet the engine's basic octane requirement, which in the case of the CRF is pretty much met by premium pump, the fuel's distillation (aka vaporization) curve is the single most important spec you should be looking at. The specific energy of the fuel is important as well, but if you can't vaporize the fuel the energy can never be released so it takes a back seat. In other words you should be looking for a fuel that has a reasonably low front end temperature range (for good throttle response) and 90% vaporization and end point temperatures low enough to allow complete vporization of the fuel at high rpm. Basic rule of thumb for high speed single cylinder engines is, any fuel with a 90% vaporization temperature greater than about 240F will make less power above 7000 rpm than a fuel with a lower 90% temp all else being equal. For the record the 90% temperature of summer gas in Illinois is in the 340-370F range. It's similar in other places. Choose your fuel wisely boys, there is more power in good combustion and proper tuning than those most of the shiny pipes people sell. Here's what a curve for a proper high rpm four-stroke MX race fuel looks like (blue line on graph) and how it compares to pump fuel. (Special thanks to Dave Redszus from Firepower Fuels / Precision Automotive Research for the graph data) [IMG]http://www.ericgorr.com/images/distillation%20curve%20graph.jpg[/IMG] [/QUOTE]
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Dirt Bike Discussions By Brand
Honda MX & Off-Road Dirt Bikes
Crf250 Fuel
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