Methanol VERSUS Ethanol - Simple question (Octane??)
 

Very quickly -

If you look at 99%+ pure methanol, versus 99%+ pure ethanol, which one has the higher octane rating?

Thanks in advance.

Mike

PS I'm not doing anything crazy, but I would very much like to know the answer.

I'm not sure, but I think they would have approximately the same rating. I remember hearing that if ethanol had an octane rating it would be about 116 (obviously not the actual ratio of octane to heptane). I believe methanol was a little lower.

so they're both well over 100 octane (rating), when pure?

I would expect methanol to combust easier so it would have a lower rating (I agree with you) but by how much, I wonder.

One will make you go blind, the other one will give you a nice buzz, but that's all I know...:o

Methanol reacts with aluminum, ethanol does not. Both react badly with most plastic and rubber hoses................teflon furocarbon liners are required inside hoses.

Since both of these are already partial preburned [oxygen in molecule].

BTU per gallon and AF ratio are important if fuel consumption is important to you

They are both well above 100 oct rating, calculated obviously. Ethanol has a hair higher octane rating than methanol, not much though, maybe extra 0.5 on the rating, maybe not even.

Ethanol is MUCH easier to work with because it's less corrosive than Methanol. They are both hard on plastics and rubber, as stated before. Methanol is also very nasty to you. There's some mixed data out there where some sources say it's a carcinogen and neural toxin where as others state that there isn't much evidence of that.

I'd say that you should use ethanol for automotive applications because it's just easier to handle. What are you looking to do? Alcy injection?

Last time I went to do 1/4 mile runs, my engine bay was heat soaking like no other, even with heat on full blast.

Next time I go to the 1/4 mile track, I am going to use a spray bottle with pure 100% ethanol, 200 proof (or maybe mix with some distilled water) and spray down my entire engine bay to reduce temps. I was looking for info because I could have used methanol as well.

Since the vapors will get sucked into the intake to some extent, I didn't want any problems, and wanted to make sure the octane rating of ethanol was high enough.

I just wanted to see which one was better, if any. Looks like I'll go with ethanol for sure.

Believe me I know the "scientific" side of methanol and ethanol, I am a grad student researcher in chemical engineering. I just didn't know the "automotive" side.

Hmmm, interesting idea. Distilled water may be better for cooling purposes. I am pretty sure it has larger thermal capacity than alcohol and will absorb a lot more energy while evaporating. Also, water vapor will not harm your engine in any way when you start driving. In fact, it will have additional cooling effects on your intake charge. Water injection is pretty common in racing applications. Unless you're after octane boosting :) In that case, just do full alcohol injection or 50/50 mix and be done with it already :D

Also, from your profile, sounds like you're NA, right? If you're on pump gas right now, you want to keep the octane as low as you can get away with for power for your current tune. Adding alcohol to the mix will raise your octane which may actually slow you down if you're already at your maximum timing profile and you're not experiencing detonation. Just a secondary factor to keep in mind. It's probably not major given the amount you'd take in but worth mentioning. As I mentioned, this is obviously all contingent on what gas you're set up for and how your car is reacting to it.

I just remembered that alcohol will burst into flames pretty easily. I should probably keep the mixture mostly water for safety, wouldn't want my engine catching on fire :D

Yes, I'm N/A, but believe me, I'm JUST on the threshold of knocking (advanced timing at 13.0-13.3 AFR). I knock on the dyno like a MOFO.

I typically add a few gallons of 100 octane when I want to really push it.

The alky will work better to un-heat soak the engine. Same way it works better in reducing temps when you run alky injection over water injection. [edit] But like you said, not safe on the outside due to **** that might ignite it. [/edit]

As far as ethanol vs methanol, I'd like to see results of that in an injection way... I know what straight meth will do, but never seen straight ethanol used for injection purposes. I wish they had eth at the pumps out here like they're getting at places in the mainland.

It's tough to find 100% pure ethanol.

Ethanol/water mixtures naturally max out at 95% purity, unless drastic measures are taken to increase purity. But 95% should be good enough for just about any purpose...

Close enough to 100%... :icon38:

But like I was saying, any clue how it would compare in an injection situation?

I don't think that is true. Water has nearly double the thermal capacity when compared to ethanol: 4.18 JgK vs 2.44 JgK at temp of 25C. That means that it can absorb a lot more thermal energy than alcohol can, gram for gram. Molar mass tells a different story but I doubt you'd be there counting the molecules :)

Alcohol/water injection is better than just water because it gives you cooling properties and raised octane. Water alone will cool better but cooling itself will yield lesser results as opposed to reducing cooling a bit but raising the octane. You end up with better results altogether with a mix or pure alcohol mainly due to octane benefits. If cooling is what you're after, it's really hard to beat straight H20.

methanol evaporates so fast that it helps with cooling because of that. You're supposed to double check you have a lid really tightly sealed on a methanol container. From what I've read, methanol that you can buy from fuel companies is usually around 107 octane. That's about as pure as I've seen it. Personally, I don't use methanol from windshield wiper fluids because it has other things added to it for cleaning purposes along with blue dye

methanol mixed with water is diluted enough to not cause too much corrosion. Having a stainless steel intake manifold or intake piping might reduce the chances of corrosion vs aluminum. I think by the time the water/meth makes its way past the intake manifold it's already dispersed itself pretty well anyway so that by the time it reaches the alluminum engine, it won't really matter much.

The fact that it cleans the intake manifold and then also if you use an oil catch can will keep the engine as clean as new. There'd be no need to use gas with additives like Chevron gas etc that helps clean the engine

Yeah, you're right. I forgot to consider the evaporation effect. Alcohol evaporates faster hence it will cool better. A 50/50 or even 60/40 mix of alcohol and water will do well for engine bay cooling.

most pumps used for water injection will not handle more than a 50/50 mix for very long and will eventually fail.

Check to make sure your pump is rated for a higher concentrate of methanol before having a stronger methanol mix

I would expect ethanol to behave better than methanol. (but like I said, I'm not an expert when it comes to automotive applications so :dunno:)

Here are some enthalpies of vaporization (not corrected to be at the same temperature though)

Methanol: 37.4 kJ/mol
Ethanol: 42 kJ/mol
Water: 46.5 kJ/mol

(these numbers give you a general idea of RELATIVELY how much heat is removed from the combustion chamber)

Since ethanol combusts nicely, and it absorbs almost as much heat as water when it vaporizes, I would think ethanol is the winner.


BUT since pure ethanol/methanol is expensive, I would think that people go with water/methanol mixtures because you will get comparable performance for much less money.

Us Evo guys have quite a few systems out now that are meth-safe. A lot used to fail because the meth would eat away the rubber seals.

Good thoughts...

I'd pay the premium for ethanol if I had to. I just want to see a tuner actually test it out as an injection first. I know of one tuner in particular (Buschur Racing) that is running ethanol fuel and is having great results, but we don't have that out here. He's actually planning on growing corn for his own personnal fuel consumption for his personal/race cars.

The trick to use here is the A/C set to low.

Turning on the A/C get the radiator fans to turn on "High". And this removes heat much faster than the heater. Setting the A/C on low puts a lower mechanical load on the compressor and puts a lower thermal load on the condensor heat exchanger. The net effect is cooling much, much greater than what the heater can do.

Turn on your A/C immediatly after a run.

And when you come to the pit area put your transmission in neutral and keep the engine reved at 1500 RPM - 2000 RPM for about 1 minute (with the A/C on). This will get the water pump to move the water a lot faster and your coolant temperature will drop a lot faster too.

After that, just let it idle with the A/C on for another 2-3 minutes. This will bring the core temperature down to about 183'F (or what ever temperature your thermostat allows)... and your ecu will give you full timing advance.

And always leave the hood open when parked.

Also make sure to use your stock intake box (no aftermarket intakes).


If you will be using it as a coolant to be sprayed on the engine, that completely eliminates any amount of methanol in the mix.

Any solution of methanol will quickly vaporize and create a blinding poison gas cloud. :icon15:
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Pure ethanol is too risky a fire hazzard.:flame:
Its very expensive but you can find it as "Everclear" in some specialty alcohol shops.
About 15% Etoh in water will significantly raise the evaporation rate and that will cool things down a lot faster than pure water...
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At 15%, you can also use IPA to achieve approximatly the same evaporation rate and cooling properties. Iso Propyl Alcohol is also a lot cheaper and a lot easier to find. As a spray-on coolant, I would go this route.


Be sure to hose down the MAF sensor housing and intake box really good because they are significantly heated by thermal radiation from the head assemblies and convective heat from the radiator. (I've seen it too many times on the dyno)

You may even want to heat wrap the stock box and MAF sensor! I did.
I did mine just so I could get consistant results on the dyno. Heat soak on the back side of the stock intake box and MAF sensor housing can kill about 6-8 HP.

The reason is because at idle all these plastic parts get HOT. And the internal air flow rate is too low to cool it off. In fact, the slow moving air is just enough to pick up heat and sweep it into the rest of the system. Including the MAF sensor. The air just before the intake can be at 80'F, and 6 inches away, the air at the MAF sensor can be as high as 100'F!

Once you hit the gas for a 1/4 mile run or a dyno pull it takes several seconds for the hot MAF sensor to cool down to ambient temperature... but by that time, your 1/4 mile run or dyno pull is already toasted.

.