|MadSci Network: Chemistry|
Greetings: The boiling point of gasoline need not be reached to have vapor lock, it is the Vapor Pressure of the gasoline that is important. There are a number of variables in the vapor lock problem. The higher the octane of the gasoline, the higher the volatility the greater the chance for vapor lock. See the Shell oil information at the following URL: http:// www.sopc.com/products/conclusion.html The boiling point ( standard boiling point; normal boiling point) is the temperature at which the vapor pressure of a liquid is equal to the external pressure on the liquid. The standard boiling point is the temperature at which the vapor pressure of a liquid equals standard pressure. Vapor Pressure for street grade gasoline ranges from 9.0 to 15.0 psi (pounds per square inch) depending on the air temperature of the environment. Generally, if the gasoline’s vapor pressure is above 8 psi vapor lock becomes a problem (see Unocal reference). The higher the average air temperature of a locale, the lower the Vapor Pressure needs to be. The lower the median temperature of an area, the higher the Vapor Pressure must be to properly atomize the fuel with air for proper engine combustion. See the Racing Gasoline Frequently Asked Questions which has been compiled from documentation by Tim Wusz, Unocal Corporation and magazine articles at the following URL for more detailed information: http://www.tgill.com/ racefaq.htm#faq3 To help you understand all these terms there is an excellent General Chemistry reference site on the Web that defines and explains vapor pressure, boiling points, standard pressure etc. at the following URL: http:// antoine.fsu.umd.edu/chem/senese/101/index.shtml Best regards, Your Mad Scientist Adrian Popa
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