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Fuel economy gas vs ethanol

  1. Mar 6, 2007 #1
    1. The problem statement, all variables and given/known data

    An automobile has a fuel economy of 25mi/gal when combusting gasoline. If the engine is modified to burn pure ethanol, but the engine effeciency stays the same, what is the expected fuel economy? If the ethanol powered engine is 10 percent more efficent than the gasoline engine, what is the expected fuel economy?

    2. Relevant equations

    I have found,

    Density: Ethanol = 800 kg/m^3
    Gasoline = 670 kg/m^3

    Also found the specific heat of combustions

    Ethanol = -29.6703 MJ/kg of fuel
    Gasoline = -45.7 MJ/kg of fuel

    3. The attempt at a solution

    I'm not sure where to start.....I think its just a matter of converting, but I'm not sure.

    I understand the second question, I just take the first answer(miles/gal) and multiply it by 1.10. I'm not sure how to get that first answer though.
  2. jcsd
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