fuel mpg alcohol vs gas

[onestout]

My experience has taught me that an engine on alcohol takes twice as much volume to get the same power (approximately), this would lead me to beleive that there is only about half as much "potential energy" in the alcohol. Is fuel efficiency strickly an energy calculation between the 2 different fuels (keeping everything else constant) or does one fuel atomize better than the other throwing in another variable? Thank you

Michael

 

[schmidtj86]

Alcohol contains Oxygen and has a stoichiometric mass air/fuel ratio of around 6:1 for Methanol; 9:1 for Ethanol. Ethanol has a specific caloric value of 26.8 MJ/kg. Methanol is 19.7. Iso-Octane is 44.6 and has a stoichiometric A/F of 14.7:1 ish. If you are looking for miles per GALLON use gasoline (more power per mass). If you are shooting for max power/cubic inch use alcohol (since it has oxygen in it - more overall energy can be released if rich enough, and has higher octane rating - more ignition advance).

 

[Metalguy]

Forget the ignition advance-go for the compression ratio!

 

[ShaunT]

Go for Compression! Don't forget the mass that Alky takes in the intake port. It is beneficial to have a little bigger port. If your port is already big, Alky will offset that a bit. If rules allow it, injection is an even better blessing for Alky than Gasoline. You have to be careful on pressurized Alky engines with respect to cams. You run a single pattern or a reverse pattern which has more intake duration than exhaust. You also run a 114LSA. If you don't do this with respect to cams, the motor will be hard to tune and will have cold EGT's. It will also make it hard to keep it lit. When I first started in Blown Alchohol, I had a partner who insisted on following the crowd. We could only get approx 900* EGT because he would not let me run a smaller exhaust cam like I insisted. I finally convinced him, and we won in '99.

Shaun TiedeULTRADYNE Arl,TX(stiede@ev1.net)