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      09-01-2012, 11:20 AM   #86
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Drives: 07 e90 335xi
Join Date: Mar 2011
Location: CT

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Originally Posted by vasillalov View Post

Plain and simple:

USA 91 fuel = 91 AKI
USA 93 fuel = 93 AKI
USA E85 = 94-96 AKI


Do not confuse E85 and pure ethanol. Totally different things.

Originally Posted by vasillalov View Post

Read those articles carefully! They are talking about pure ethanol, not E85. Like I said before, there is a big difference between pure ethanol and E85 fuels! They ARE NOT the same.
So yes, you are still propagating a lie!

Those MIT articles indicate that in a direct injection application the effective octane of pure Ethanol (R+M/2) is 160. That is a pretty big difference from the 99 you cite from Wikipedia but don't forget though that according to the standards used those values were NOT determined for a direct injection configuration. For example ASTM standard D2700 - 12 (for measuring MON) as well as ASTM D2699 - 12 (for measuring RON) calls for a carbureted engine to be used in the testing!

From that same MIT article,
It should be noted that direct injection of gasoline also increases the effective octane of the gasoline, but to a much lower degree than for ethanol or methanol.

Ford claims that even just direct injecting E85 as a supplement to regular gas port injection can raise the effective octane to over 150. The numbers are probably a little optimistic given this is a new technology they are trying to develop but it is good information none the less...

So if we assume that,
1) The gasoline the ethanol is blended with is 87 octane
2) We can ignore that the gas will see an increase in effective octane from DI
3) We are getting the lowest allowed concentration of ethanol in E85 (68% per the DoE Handbook for Handling, Storing, and Dispensing E85)
Then using MIT's numbers, in a DI setup, we should still get an effective octane of about 136.

So perhaps the difference between E85 and E100 is not as great as you think.
2007 335xi 6AT | Cobb Stage1+ | BMS DCI | VRSF 7" IC | FA 500 400#F/600#R | ARC8 17x9 et30 | RE-11a 255/40/17

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