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You're wrong. If you were dealing with equally efficient engines, then you would be more right, but changing the compression ratio also changes how efficiently the engine extracts useful work from the available energy in the fuel.
It is not really feasible to build a commercial engine that is so much more efficient running on ethanol that it will get more mpg than an equivalent power gasoline engine; but the difference will be less than a straight comparison of btu/gallon would imply, and there are some interesting laboratory alcohol engines that approach diesel efficiency. E85 will never be mandated as a marine fuel for the simple reason that if you get too much water in E85, then the gasoline will separate from the water and alcohol. Neet alcohol, with no added gasoline, is a better marine fuel, but still unlikely to ever be mandatory. If biodiesel produced from algae becomes economically and environmentally sustainable, then market forces may gradually result in a de facto shift of marine power to diesel, but it still won't be mandated. The total amount of fuel burned by high-performance boaters simply isn't very great when compared to the total of all transportation fuel usage, so there just won't be all that much pressure for mandated marine fuel changes. On the other hand, you may well see a carbon tax added to your fuel bill. |
Originally Posted by outriggers
(Post 2456822)
I was always thought that if the btu's per gallon were less so was the mpg, no matter what the compression. Less energy per gallon so you have to burn more of it to make the same power. Am I wrong? Doug
BTU/lb (energy Content) are based on the weight of the fuel, now you have to combine that with the amount of fuel being used (Air Fuel Ratio) to get your total BTU (Total Thermal Energy) Here is some simple Chart that I had, I'll do the math on E85 later but it winds up between gasoline and methanol. lbs of air (lbs) A/F Ratio Pounds of Fuel (lbs) Energy Content of Fuel (BTU/lb) Total Thermal Energy (BTU) Gasoline 42.64, 12.8:1, 2.89, 18,500, 53,176 Methanol 42.64, 6.0:1, 7.11, 9,500, 67,545 Nitromethane 42.64, 1.7:1, 25.08, 5,000, 125,412 As you can see the fuels with lower energy content put out more total BTU's sinces the overall volume is that much more due to the Air Fuel Ratio... |
Originally Posted by Payton
(Post 2456617)
Why are drag cars so much worse? Indy cars went to Straight Ethanol last year and were able to make the fuel tank 20 gal instead of 30. US auto makes will have to switch to more turbo charged engines. The the milage goes up with ethanol, not down.
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Originally Posted by Payton
(Post 2456617)
Why are drag cars so much worse? Indy cars went to Straight Ethanol last year and were able to make the fuel tank 20 gal instead of 30. US auto makes will have to switch to more turbo charged engines. The the milage goes up with ethanol, not down.
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all this sounds great but all i know is years ago when i was dragboat racing when we took a blowngas boat and changed it to run on methanol the first thing you had to do is double the fuel going in to the motor and go up on boost. yes power came up but if we had left the boost the same and nozzles the same we would have leaned out the motor.
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To produce and deliver 1 gal of ethanol uses 1.27 gallons of gas. Yea, real good idea.
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That's not true. Even corn-based ethanol does not take more energy to produce than it yields.
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Whatever you say Al, do the research.
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I have.
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Originally Posted by formula31
(Post 2456963)
To produce and deliver 1 gal of ethanol uses 1.27 gallons of gas. Yea, real good idea.
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