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Motorcycle Myth #2 Summoning the gods of combustion speed
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[QUOTE="Rich Rohrich, post: 1480436, member: 16241"] First of all, I can't think of any situation where slowing down the combustion rate would be a good idea. The longer the reaction takes the more time the mixture is exposed to heat and pressure which brings it closer to the fuels auto-ignition threshold. Based on what I know about the readily available legal hydrocarbon based fuels and additives in the US, there is nothing you can do to significantly impact the speed of combustion with the fuel alone. Carcinogenic additives like propylene oxide have been tried in the past to speed up reactions and increase horsepower in some applications but the associated problems far outweighed any advantages gained. Combustion speed comes from mechanical design considerations and as was pointed out by another post, the homogenization or uniformity of the mixture. A uniformly mixed charge with a minimum of already burned charge left over from the previous cycle makes a huge difference in the combustion speed. You're a two-stroke guy so I know you're likely familiar with the difference in the octane requirement of an engine that you've gotten the transfers and scavenging dialed in on versus one that's a bit off. When the scavenging is bad the combustion speed slows down and the knock free octane requirement goes up. The paper cited below is four-stroke related but it has information that is universally valuable. I read it in high school when it first came out and it helped me understand a lot about the combustion process and how fuel plays a significant role. It's worth a read for those who want more details. [HEADING=2]Research and Development of High-Speed, High-Performance, Small Displacement Honda Engines[/HEADING] [HEADING=2]SAE paper # 700122[/HEADING] Abstract : Honda has produced high-speed, high-performance, 4-stroke cycle gasoline engines by applying advanced technology gained through the design and development of motorcycles and automobiles for Grand Prix racing. Some of Honda's racing engines attained performance as high as 260 bhp/liter or nearly 4.3 bhp/cu in. at speeds of up to 25,000 rpm. This paper describes our technical approach for optimizing combustion efficiency, volumetric efficiency, and mechanical efficiency-the keys to high-speed, high-performance engines. [/QUOTE]
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Motorcycle Myth #2 Summoning the gods of combustion speed
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