For the alcohol gurus...

[USA_muscle]

Here is a question I have been pondering after seeing a post on the octane ratings of the different alcohols. With price not being a factor, is one of the common alcohols better than the other (ethanol vs methanol vs isopropanol) for injection or does it make a differnce? Could they all be used straight up? I know methanol can but I have not heard of any of the others straight up, only in mixes (typically with water in a 50/50).

 

[GNBRETT]

Methanol. Been discussed. You can search that question and many threads will come up.

 

[bison]

Methanol has the highest latent heat of vaporization combined with a low boiling point so the least of it could be used to achieve the same anti-detonant response compared to other alcohols. All the ones you mentioned are acceptable but may require more flow as engine hp increases to prevent detonation. If you are concerned which has the most energy per lb then there may be better alcohols to use than methanol. Im not sure on the amount of energy each has per weight. For anyone who is injecting it to prevent detonation vs using it as the primary fuel i doubt you would be able to tell the difference between them as long as enough was delivered to prevent detonation and the a/f's were the same. Ive used methanol, ethanol, and isoproponol straight all with the same result. Methanol is the cheapest and easiest for me to obtain so thats what i primarily use. Also keep in mind unless your storing the alcohol in a sealed metal container then its absorbing moisture and changing the energy value per lb. A windshield washer bottle is not going to prevent moisture from getting in the alky. But being used as an anti-detonant it doesnt seem to matter. Ive use the meth that was in my tank for 5 months and it still worked.

 

[USA_muscle]

GNBRETT

Thanks for the quick reply.

I did a search and read several posts. However, I did not see any physical data (I ran ethanol and had X et then drained and ran methanol and had X+ et; or changes in dyno numbers, etc). Most say "I run this type because it is better", or "that is what most run", or "it felt stronger with meth" etc, etc. Is there a post, link or data that you know of that I could look at? I will keep looking through the search results.

 

[USA_muscle]

Tahnks bison,

I just found a post from 05 that explained what you are talking about. I have been using methanol since I purchased the car in June, but have access to all of the 3 types I have mentioned (price difference very close). The safety edge of methanol (vs detonation) that has been talked about makes it very attractive, I was just having a hard time finding any real world numbers to say one is better than the other or there is no dicernable difference (performance wise).

 

[Razor]

Ive had better detonation suppression with methanol over the ethanol(denatured). No power increase using one over the other.

Until you get knock with the ethanol.. then power will be down.

Just depends on how much boost you run.. and how aggressive you tune it.

 

[Alky V6]

Finding the chemical properties of the different alcohols should not be that hard to find. Bison already explained the latent heat of vaporization and the boiling point. That alone should make it the attractive choice for detonation suppression.
Another good point is the real world octane level of methanol. When used correctly, up to 125-130.
The basic btu per mole weight is a little misleading if you don't take into consideration the optimum best power a/f ratios of the different alcohol fuels. Methanol has it over the others in this arena also.

 

[bison]

Finding the chemical properties of the different alcohols should not be that hard to find. Bison already explained the latent heat of vaporization and the boiling point. That alone should make it the attractive choice for detonation suppression.
Another good point is the real world octane level of methanol. When used correctly, up to 125-130.
The basic btu per mole weight is a little misleading if you don't take into consideration the optimum best power a/f ratios of the different alcohol fuels. Methanol has it over the others in this arena also.

Alky seems to be more forgiving as far as loss of power than gas if run on the rich side from what ive seen. If using alky injection to suppress detonation id rather be safe than sorry.

 

[Alky V6]

You're correct, Bison. Methanol has a very broad tuning range compared to gasoline. Another nice thing about methanol, when running very rich mixtures, you don't have to deal with carbon buildup on your racing spark plugs.