- Jan 11, 2009
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- Thread starter
- #21
True enough Nik. Octane does not equal energy. Only resistance to detonation. Now for ethanol, that does have a different amount of energy than fuel at approximately 80%.
Octane Required
- Thread starter Riley P
- Start date
- Jan 11, 2009
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Yep, I thought it was even less than that for ethanol. On the flip side great power adder if you do the conversion and can pump enough of it, oh and you happen to refine it in your backyard.
- Jan 11, 2009
- 11,104
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- #23
Agreed. I believe it's somewhere around 80% the energy of gasoline but could be off a bit.
Octane's advantage is how the engine uses that resistance to detonation. The computer can take advantage of higher cylinder pressure to fire the spark plug for peak performance. You can build an engine with a higher compression ratio or forced induction and the fuel with the higher octane can resist detonating prematurely allowing you to make more power. As for E85, ethanol has a really high octane level. As mentioned before, less energy than gasoline, but higher octane so people use E85 to run crazy boost pressures in their engine to make some huge power.
As for the debate of "E10" fuel, if ethanol only has 80% of the energy of gasoline, and the fuel is 10% ethanol, then you're technically only down 2% energy wise compared to straight gas.....but for some reason, I still refuse to use ethanol if I don't have to.
Octane's advantage is how the engine uses that resistance to detonation. The computer can take advantage of higher cylinder pressure to fire the spark plug for peak performance. You can build an engine with a higher compression ratio or forced induction and the fuel with the higher octane can resist detonating prematurely allowing you to make more power. As for E85, ethanol has a really high octane level. As mentioned before, less energy than gasoline, but higher octane so people use E85 to run crazy boost pressures in their engine to make some huge power.
As for the debate of "E10" fuel, if ethanol only has 80% of the energy of gasoline, and the fuel is 10% ethanol, then you're technically only down 2% energy wise compared to straight gas.....but for some reason, I still refuse to use ethanol if I don't have to.
I actually did read your comments and the fact is the manual does not recommend 91 octane for best performance. It recommends 91 octane fuel as a minimum. listed in the manual in section 9-53.
I will agree with you that there is no HP gain above 460 using higher octane fuel because what will actually happen if you run poor fuel or low octane fuel you will lose HP. The engines management system will retard the timing adjust the valve timing and try to eliminate the detonation.
The goal is always to get the most HP out of the engine on a given day with the weather and altitude factored in. Unless of course you have a Turbo or Blower then who cares about altitude.
The most important thing we can do for these engines is run the correct oil and good fuel in them. No one will disagree with that statement I hope.
Later....
- Aug 30, 2014
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OMG. Someone else that has actually read the manual! 