Almost every post where people talk about E85, they seem to think the octane rating is 105 comparing it to 93 octane gas using (R+M)/2.

There is no source I could find that stated an (R+M)/2 of 105?
It is 95-97 depending on winter-summer blends, and even lower if its the new 51% winter blend in some regions.

The octane rating of e85 is good, but its not that good. The reason e85 is so good is because of its cooling properties which aren't represented very well in the octane rating.

The Enthalpy of Vaporization per unit mass at room temp of Ethanol is 2.6 times that of gasoline, this means it basically takes 2.6 times as much energy(mostly heat) from the air to vaporize liquid ethanol to a vapor versus gasoline. That's how ethanol is so good at combating internal cylinder temperatures and hot intake air to reduce knock. This is also why in colder weather it is harder for high blends of ethanol to start. The fuel has difficulty vaporizing so that it can burn.

 

What You Need to Know About E85 Ethanol Alternative Fuel - Hot Rod Magazine

 

Hot rod is wrong its not 105

http://www.afdc.energy.gov/uploads/p...l_handbook.pdf

 

The Reaearch Octane of E85 is 105, not the (R+M)/2, the Research octane of premium gas is 97.

If were going to say E85 is 105 octane then we need to say premium is 97

 

Who gives a flying what the calculation is, when you running a 105 octane gas variant you get to the same timing as running e85.

And honestly I have yet to see any actual tests of e85, just forum posts.

 

Just thought I'd give some insight into why it performs as well as higher octane gasoline. Just interesting to know why instead of just saying is better

 

It's cooling effects are well known and why people run it, you see no significant increase in timing after about e50 on port injection and around e60 on direct injector. Only reason people run straight e85 is for cooling or laziness at the pump since most states and stations don't have ethanol mixing pumps

 

Stuff is pretty amazing, I'm on E30 right now with a 24-26 timing curve.
It started raining so I still need to try adding some more. Also might add a little more E as well

 

Call me old school, but I'll always love my race gas.

 

Call me cheap, I like 1.85 per gallon better than 7 per gallon

 

Your cheap. And corn is magic.
Octane doesn't take magic corn into account.

 

 

My car runs on double magic, since the first bit of magic happens at the turbo and then the second happens with the corn juice

 

Mine runs on pixie dust!

 

$7/gal?!?! I'm coming to where ever you are to get fuel then! Cam2, or anything comparable, is right around $12/gal out my way.. lol

As far as the octane ratings go. Although I'm clearly not a chemist, nor do I care to have the equipment or no how to test and compare octane ratings in fuel, I can at least share this much.

A few years ago I did a pretty in depth test,comparing an array of fuels and concentrations of the fuels. I'm not going to write an entire paper on the matter atm so, long and short of it....

Unleaded and oxygenated Cam2 (100 octane, 105ron 95mon) produced less hp and could not take as much timing as even e47-e50 blends of ethanol. The most noticeable power drop off was in torque and seat of the pants driving. Granted, there are far more potent versions of race fuel than 260GT out there, but they're also not very emissions friendly, or wallet friendly for that matter. For me, unless you go for the "big boy" juice and are going for serious power, it's just not worth spending the money on actual race fuel.

On a side note.... There's nothing like the smell of running race fuel though!! lol

 

Good info^

VP109 is my new poison

Much better than just regular old CAM2 and similar price out by me.

 

The 7 per gal was what the I think it's 101 octane by me is, one station has a race fuel pump. Used it once to raise the octane when I was figuring out if real or phantom KR and it was near 9 per gal then (93 was like 3.50). Can't save I've ever looked into cam2, not even sure who produces it, out here we normally only have VP Fuels