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I don't know much about it other than its about 105 octane. some like it and some don't.



It is been said by many that E85 has an octane rating in the neighborhood of 103-105 octane. However in an excellent, often updated publication put out by the Renewable Fuels Foundation “Changes in Gasoline IV the Auto Technician’s Guide to Spark Ignition Engine Fuel Quality” they have this to say.

“The often cited 105 octane for E85 is incorrect. This number was derived by using ethanol’s blending octane value in gasoline. This is not the proper way to calculate the octane of E85. Ethanol’s true octane value should be used to calculate E85’s octane value. This results in an octane range of 94-96 (R+M)/2. These calculations have been confirmed by actual-octane engine tests."

That may seem like a low (R+M)/2 octane rating in relation to racing gas, but is a bit misleading due to the cooling properties of ethanol. E85 does have an octane rating higher than that of regular gasoline's typical rating of 87, or premium gasoline's 91-93 to be sure, but not by much. It’s this cooling effect of ethanol’s rapid evaporation rate that allows it to be used in much higher compression engines than one would think when you compare its detonation resistance qualities to that of gasoline. It’s these very high static compression ratios and the allowance of optimum cam timing events to produce the higher running dynamic compression ratios that produce more power per unit of displacement than their 100% pure gasoline counterparts with similar or even higher octane ratings. This is despite the fact that there is 30% less BTUs per gallon with ethanol, as long as the subsequent fuel and air delivery increase requirements are met.

I have watched closely at some of Darren Teddar’s mega inch E85 Hemi builds over the years. IIRC, I think he ended up with around 15.7-16.0 static compression on the 656” Hemi. That was with a 4.560 bore and piston with a wide,flat quench area. The small chambers of the Stage V Millennium heads allowed for a good squeeze without a mountain size dome that would tend to shroud the flame front. North of 1250 HP with a fuel that costs 20-30% of what an exotic racing gasoline would cost to support that kind of compression is impressive. I would think that a wedge engine that has a similarly large quench area that provides an aggressive squish and turbulent burn, would be even more successful at these high compression ratios than a Hemi that traditionally has fairly lazy burn characteristics

Whether you want to deal with the corrosive qualities of the fuel or not is a personal decision, but E85 is a viable alternative.


Ed.