mk1spitfire

And why?

NM2K

My Feedback: (14)

It depends. <G>

Which delivers the most power, burned under ideal circumstances at sea level atmospheric pressure, temp and humidity for a given amount of fuel? Petrol (gasoline) easily outpowers methyl alcohol. Why? You'll have to ask a chemist or a petroleum engineer. I'm not into long chain theory and the like.


Ed Cregger

vpresley

My Feedback: (162)

In Laymans terms without all the double talk, Gas burns hotter than alcohol, more heat, equals more power. Not going to get into all the possibilities there are with all the different systems and such, just keeping it simple.

Jim Thomerson

Methanol. How much power you get depends on how much air you can run through the engine. Methanol contains less energy than gasoline, but burns with more air so that, If I recall correctly, methanol gives about 8% (3%?, whatever) more power than gasoline. This is why most of the guys who fly antique sparker engines run glow fuel rather than gas and oil. Gasoline will give better fuel economy, however.

wcmorrison

My Feedback: (2)

It boils down to BTUs per pound of fuel. Pertrol (or gasoline) has about twice the number of BTUs per pound of methal alcohol. So it amounts to the amount of energy available in the fuel. For instance, JP-5, a kerosine, has more BTUs than JP-4 (wide cut gasoline). JP-5 is heavier than JP-4. Some would refer to it as latent heat avialable, gasoline has more energy that alcohol, ergo it has greated latent heat available.

The early model engines all used petrol with oil mixed in. Alcohol came along when someone thoughtfully realized that acohol would keep a platinum filament glowing. That meant one no longer needed an ignition system and time devices to make the engine run. So it was a boon to small engines. When it comes to big engines, there is a lot of power to carry around flywheels with magneto type ignitions. Of course, today, we have solid state electronics that do alll the timing and supplying spark energy, making gas engines even lighter.

Cheers,

Chip

martenson

I'm just an old dragracer.
I run a petrol racecar, and I KNOW the same setup on alchol (methanol) would make more power, but not in the same setup.
Nitro makes more power, more oxygen in the fuel.
I have in fact tried nitrous oxide on a standard glow engine with 80/20 FAI fuel and it picked up ALOT, 4-5000 rpm in a short burst.
Longer it would have melted the piston, when I could not put more fuel to the NOS.

Good luck

TFF

It is a double edged question. Gas has more btus per unite, but the engine wont run per unite; it has to run to a stoiciometric ratio. Gas is about 14 to 1 and methanol is about 7 to one. With that there is a little more btus at the correct ratio for methonal so it is more powerful, but with less run time. If you want milage, you can trade less power for more run time with gas.

ArcticCatRider

My Feedback: (6)

If gasoline as some say produces more power than methanol, why are topfuel dragsters all burning alcohol??

I think I heard once that methanol requires less oxygen to burn than gasoline. So, if you have an engine that can suck x-amount cubic feet per minute of air, the limitation is how much fuel you can put through it and still have a correct mixture.

Since alcohol requires less oxygen to burn, you can put a lot more alcohol through that same engine that you would be able to using gasoline...yielding more power. I think this reflects what I've heard before.

But not I'm interested...and would certainly like to be corrected if I'm wrong! Good thread!

jessiej

No, just the oposite.

jess

Sport_Pilot

People are confusing heat with power. Gas has more heat per unit. But power is measured by moving something over a fixed distance in a fixed amount of time time. You can burn gasoline and methanol in a torch and the gasoline will give off more heat, but if you burn them in an engine you can run a much richer mixture of methanol. So much that the methanol will produce more power.

captinjohn

I would say wide open running the alky is the only way to go...far better cooling effect with a 2x dense mixture...that means engines hold together better. My @ Cents Capt,n

MJD

My Feedback: (1)

It's not that difficult.

Methanol burned at stoichiometry with air produces less energy per pound of fuel than gasoline does at stoichiometry with air - yes, that is true. But that fact refers to units of mass, and has nothing to do with the state of matter.

Methanol burns at a higher fuel:air ratio than gasoline (not "richer" than gasoline, rich or lean is relative to stoichiometry, not the numerical ratio) and here's why it wins: The ratio of the increase in density of a stoichiometric methanol/air mixture versus a gasoline/air mixture, is greater than the ratio of the decrease in chemical potential energy per respective pound of fuel/air mixture.

An internal combustion engine inhales a specific volume of fuel/air mixture per stroke - not mass, but volume. The same volume of methanol/air mixture releases more energy than the gasoline/air mixture. Therefore at a given rpm, more energy is released per unit of time which equals more power.

Think mass flow rate x energy per pound.

MJD

DarZeelon

Most of you there are wrong...

While it is true methanol has less BTU per pound than gasoline, its stoichiometric ratio is much lower than that of gasoline.

From Brian Hampton's [link=http://home.wanadoo.nl/pereivers/fuels_1.htm]fuel page[/link] (that's downunder - if you did not know), methanol has 9,970 BTU/lb. and gasoline (petrol) has 19,000 BTU/lb.
But the stoichiometric ratio, at which these fuels burn almost completely, are 6.44:1 and 15.0:1 respectively. This means the amount of methanol burnt is 2.33 times greater than the amount of gasoline.

This would eventually mean the same amount of oxygen, chemically combined with methanol, will produce 22% more BTUs, than when combined with gasoline.
The amount of air per cycle is the constant that limits power, in a naturally aspirated engine. Adding more fuel will just cause the engine to emit more unburnt hydrocarbons.


So, burning straight methanol will give you roughly 22% more HP than gasoline, while being consumed at over twice the rate.



So, methanol definitely produces more power than gasoline, when combusted in an internal combustion engine.

martenson

I agree with Dar.

A topfuel dragster only run on 10% methanol and 90% nitro.
And a 500 cui blown engine can make 8-10000 hp.
The same engine with 100% methanol makes ~3500hp

pe reivers

Ditto Dar, save for minor details in the numbers, since we do not want to run stochiometric mixtures, but max power mixes..
In addition, the methanol evaporates faster, and has more evaporation heat than gasoline, thus provides a much colder charge, which is more dense.
In real world, the exact same engine but jetted for methanol will produce 15% - 20% more horsepower, and will run cooler than gas to boot.
Alky allows a much higher compression ratio. That would allow a further 5% increase in hp.
Alky and nitromethane are good friends; the nitro regulates the combustion, and adds some extra oxygen to the brew, so even more fuel can be burnt per cycle. There's another 5% to be had (all at same rpm for good reference)

MJD

My Feedback: (1)

Other than numbers, I think that's exactly what I just said..? The volume of fuel/air mix is constant, not just the air volume. At low air:fuel ratios the volume of fuel vapor becomes significant in comparison to total aspirated volume.

MJD

daveopam

My Feedback: (9)

I learn something everyday on RCU. I knew the answer but not the science. Now if I read through these 4-5 times I will know the science :-).... maybe

David

azflyer-RCU

My Feedback: (5)

A few of the guys got it exactly right .... though gas has more btu,s per pound you run more than twice the volume of methanol over gas for any given engine that either fuels are tuned to ....... hence the definitive answer ... give me 2 identical engines , you set one up to run on gas I,le set one up on alcohol .... mine will have more power , over 10% more

NM2K

My Feedback: (14)

Not per unit of measurement, say a pound (weight).

If alcohol is so great, why aren't airliners, general aviation and even tractor trailers burning methyl alcohol instead of some form of petroleum?

My point is that there is no simple answer to the OP's question, unless you're simple yourself. Qualifications/specifications/criteria must be established before a proper answer can be given. But the OP knew this. That is what his/her post was about in the first place.


Ed Cregger

DarZeelon

True, MDJ.


But stoichiometric ratios are mass-to-mass. 22.5 cubic decimeters of air; almost six gallons, weigh just 29 grams.

This is enough to oxidize two grams of gasoline, or 4.6 grams of methanol.


Fuel comes into the cylinder as finely atomized droplets; not in gaseous form and not as vapor. So about 99.983% of the incoming mixture volume, in a glow engine, is just plain air.

pe reivers

Ed,
Airliners do not only want power, but they want the least weight to carry the payload (you) around. Ancient airliners had diesel engines just for that purpose, (most BHP per unit of fuel weight!) but that is not the subject of this post. The question determines the answer.

Rudolph Hart

Good question mk1.My original careless thought was who cares? i love the smell of saitos burning nitro then i started reading this thread and it gave me a headache.Looked at dars fuel page link and now it's turned into a migraine.In an effort to relieve that are you a petrochemical engineer? and what engine fuel do YOU prefer,i'm off flying,cheers

NM2K

My Feedback: (14)

I know what you and Dar are saying is true, Pe'. I just provided a sound board for others to bounce their ideas off of - er - something like that.


Ed Cregger

Jezmo

I know what the science says but I've never been able to produce the numbers in real life situations. I've raced automobiles since I had a drivers license and in various stages we switched from gasoline to methanol and then later back to gasoline. The engine rules remained the same and per said rules the compression ratio could be set at any amount. I could get a solid 10% improvement going to methanol and sometimes a little more but I never achieved 15%, at least not consistently. Now on methanol with Nitromethane added (that wasn't legal but we won't talk about that as I would never "cheat") it was a whole new ballgame. I ran compression ratios as high as 16:1 on methanol without issue but found that the pumping losses associated with the increased CR tended to kill the HP gains. Roughly speaking, anything over 14:1 on a 358 ci engine gained very little if anything at all and in some scenarios actually lost power. Ahhh, those were the good old days but man did I spend a ton a cash on that hobby. This one is much much less expensive.

Motorboy

Fuel consumption in a methyl alcohol powered engines are not economical in mileage in commercial use, also the engines are drinking more fuel cause low BTU in fuel.

Today the farmer are using biodiesel from his farm who are used in his tractor, it means he will save money to run the biodiesel instead buying the autodiesel. Now we can see the owner of diesel engine powered cars are running at biodiesel cause low price. Mileage are about same.

I has some model engines who are driving at petrol, the fuel economy are better than a methanol powered engines.
See the pic of my engine, the fuel needle are turned 1/4 from closed position, not much petrol compared with the methanol powered engine who need more turns at fuel needle to run.

Petrol powered engine: Low fuel consumption and less power.
Methanol/nitro powered engine: High fuel consumption and more power.