jobberone

I've been discussing this on another forum and I'm still confused. So I thought I'd bring it over here and get straightened out.

Here's what I know:

Ethanol is an alcohol so will mix with hydrocarbons and water.

Ethanol is synergistic in boosting gasoline octance ratings.

Ethanol has a higher equivalent octane rating than most gasolines. Maybe all????

5-10% is run in the US. Some countries use 20% which could damage some US built engines.

What I don't know is this:

What is the equivalent "octane" rating for ethanol? I've found several numbers but I'm not sure about them. Obviously it is not a hydrocarbon so does not have a true octane rating.

How much does 10% of as pure ethanol obtainable boost the octane rating using 91 octane pump gas in general? Discount all additives put in gas by different distributors. What formula do you use?

Why is ethanol synergistic in boosting "octane" ratings?

How much ethanol can you run in a regularly jetted carb before running lean?

How does the ECM compensate or does it for higher than 10% ethanol assuming heads not specifically designed to run very lean mixtures?

Is there a difference in running ethanol in more direct injection engines and can they run higher ethanol levels?

What gets damaged by running 20% ethanol assuming 10 to 1 CR and modern vette LT1/LS1 engine components?

Evil_Bob

I am not totally sure on this, yet recently I heard some information that stated the octane rating on ethanol can be as high as 103. But I didn't see any hard evidence on that rating.

The information was related to a topic discussing the idea that ethanol probably wouldn't end up as a main-stream fuel. The topic was stating that ethanol was simply being used as a crutch to help the financially troubled farming industry.

Where I live, ethanol is widely used and found at most service stations. And I have had no problems using the different fuel mixtures in all of my vehicles.

Darkness

I just use toluene as an octane booster. Toluene by it self doenst have any octanes but it acts the same.

Dr. Dirt

Well, I don't know everything about ethanol, but know a thing or two.


I beleive the octane number is the 118 seen above,

Ethanol is "synergistic" in that it has a higher number and will mix with the fuel. It boost's octane rating just like any other octane booster, the more you use, the closer you get to its 118 rating.

Ethanol has a couple of drawbacks. 1. It tends to degrade the elastic materials used in o-rings, expecially at higher levels. 2. It has been shown to be more corrosive to engine parts than pure gasoline grade hydrocarbons. 3. It has roughly 60% of the energy per gallon that gasoline has so it takes more fuel (less mpg) to generate the same power. 4. You mentioned it goes into water (aka beer), it also allows more water to be dissolved in your gas, this could lead to other problems if the water volume becomes too great.

There are plenty of engines set up to run alcohol, but simply adding it to your gas probably won't gain much unless you need an octane booster because of high compression and then I would research some others. If you are building an engine from scratch, by all means, design it the way you want to use it.

Rou-Rou 03

I believe GM recommends not using ethinol or methanol mixed gas in C-5