Random definition: The specific heat (also called specific heat capacity) is the amount of heat required to change a unit mass (or unit quantity, such as mole) of a substance by one degree in temperature.
The key term in there is per mass/quantity. When you can shove more than twice as much alcohol down a motor's throat without bogging it you end up with the capacity to absorb more heat. Hell...you can run a motor on pure alcohol if you'd like.

And latent heat of vaporization? That doesn't carry much weight in this particular application. So it takes twice as much heat to turn it into a gas. I don't think either fluid stands much of a chance of staying in liquid form when cruising thru the combustion chamber. Hell if anything the alcohol may become gaseous in the intake tract if the charge air is hot enough...and if you know anything about physics you'll know that it requires more heat to force the phase change than the specific heat alludes to.

 

oh, i dunno for sure if water is actually better than alcohol or not, but i take offense when you say you can't add enough water to make use of its properties. And by take offense I mean don't take offense, because water injection is just what I've concluded to be better based on research I've done. Your argument in favor of alcohol does sound logical, but it is not yet convincing enough for me.

 

The key with alcohol (methanol or ethanol) is you have to go big or go home. If you don't spray enough to where you have to lean out the gasoline significantly then you're better off with water. It takes a decent engine management system to be able to take full advantage of external alcohol injection. You can get some gains with alcohol if you're running something simple like an AFC2 (and running a little too fat) but boost based fueling and a wideband O2 with some sort of datalogging makes the combo lethal and capable of relatively big power on 91-94 octane.

 

Um, yes it does require more heat to force the phase change than the specific heat alludes to. The amount of heat required would be the latent heat of vaporization.

 

I would say the same is true of water injection. You can put it in as added protection against detonation, or you can tune for it and raise your PSI to (seemingly) ridiculous levels while running at optimal air/fuel ratio on pump gas.

 

Ummm...not so much.

You can only put so much water into a motor regardless of boost. After that point it starts to lay down & makes less power. Yes more boost will allow you to atomize a hair more water...but its not a significant amount. There is a practically vertical wall there.

With alcohol you can run as much concentration as you feel like tuning for...theoretically up to the point wherel you're sustaining combustion on alcohol alone mid-80's Formula 1 style. Methanol + 1.5L 4 cylinder + 79.8 psi = 1300 HP

 

"you can only put so much water into a motor regardless of boost"

That "so much" in my opinion is high enough that it doesn't really matter. My point is, say I want 10 PSi, water will give me a ceiling of 20 PSI, and methanol will give me a ceiling of 80 PSI. What do I go for then? When you compare "free" vs. "very expensive" the decision seems clear to me.

Money is a very large factor when I say I like water injection, in case you haven't noticed yet, haha...

 

The point to this thread is at least to get some of the myths dispelled. Water injection in my opinion is a great way to supress knock, on a budget. But in my opinion, if you have the ability, alcohol or meth is a much better solution. Again, this is all open to personal interpretation. You can use the system that you feel is right for your application.

 

I also have a few questions:
How much does a gallon of the alcohol cost?
Like you J-Rat, I plan on running 17 psi, but on a BNR stage 3 turbo and just for racing. (12psi daily)....so would there be a point to spraying when I am running 12 psi? Would it be better to setup a system to spray from 12-17 psi?
Do you have any idea of how much harder it is to tune your car on it? (I plan on tuning my own car with some friends help)

 

About 9 dollars and I dont think my tank is 1/2 gallon, I believe its smaller.

I run 17 psi ALL the time. I dont like to delineate between a "street" trim and a "Race" trim. My car is all go, all the time.

Sure, you dont have to be pushing 12 PSI to reap the benefits.

I am going to let my tuner answer that question.

 

I feel that I should point out another important fact.

Anytime you run ancilliary injection, IE water/meth/booze on a used motor, you incur an initial risk of dislodging carbon. The injection of these liquids WILL clean out the carbon your motor, to a signifigant degree, and you run a minimal risk of carbon lock.

Dont say I didnt warn you...

Rat

 

Everyone I talk to about these systems states that water is a much better detonation deterant then methanol. I will admit that i dont have any facts to state this other then the heat of vaporization argument. Being that i dont have any plan to tune for the water injection due to the risk of something failing/clogging. I was on the other hand thinking of toying with a mixture of methanol and water. I mainly want to do that due to when winter hits, i dont want to have to take the system out of the car due to water freezing so easily. So i figure if i get a say 25-50 percent mixture of methanol I should be good. I cant really use the water is cheaper argument because I can get methanol for free from my father.

Adam

 

Another thing I just remebered, do I run that high of a risk of messing my motor up running 17 psi without alc injection? I'm poor :P and probobally can't afford to run it for another 6 months.

 

Of course its a better detonation deterrant, its not conducive to combustion. Why do you think they use it to put out fires? The point here is that Alcohol and Methanol can give you the same benefits of water, while actually freeing up more horsepower. How is that possible? Because you can add as much of this to the engine as you feel like, because its a fuel. With water, you are limited as to the amount you can add before you start blowing the spark out.

Either way, people are going to run whatever system they feel is the best. I am just stating why I feel alcohol is superior to water.

 

17 PSI on pump gas is foolish at best..

 

You almost had me convinced, J-Rat, that methanol was a better choice... I can't give you an argument that will end all arguments, because I'm not yet 100% convinced that water beats methanol. But at least I can give some more points in favor of water.

Adding methanol will increase risk of detonation, because it is burning. That is why running methanol/water with more than 50% methanol will start to reduce its knock-decreasing capabilities. Though methanol is certainly great to prevent freezing in the winter.

Furthermore, once you have reached the correct air/fuel ratio, adding methanol has then the sole purpose of cooling. And this purpose is better served with water (which takes up half the space) therefore allowing room for more air/fuel. Though the methanol also helps cool the intake charge, therefore increasing charge density. Hmm...I wonder if the two balance out.

With water injection, you will certainly need a CDI box to get a stronger spark. Want to start pushing the limits? Then you'll need an even stronger spark system. The limitation is your spark not being strong enough, not the water. Though other limitations of course will also be engine internals and whatnot.

 

You'll be even poorer when you have to rebuild your engine. How much does it cost to lower your boost?

 

that sucks....I guess I'll stick to 12 psi for now. I still have to figure out my ems before my car even puts down any power :P I see people run 15 psi on 91...is that bad too? =/

 

Hmmmm, how about alcahol injection on 87 octane and only 10 psi?

 

But basic physics, and fluid dynamics on paper say other wise. Water does not burn period. If you increase this thresh hold you are losing fuel to compensate the volume place holder of water. In this case the brake down of less fuel less power.

"The actual number place values are fictional to serve as a demonstration."
C = combustion volume
W = volume of water
F = volume of fuel
A = Air

If C = 20v And A = 15 And F = 5
Then
C = 20
Causing a complete AF mixture

Now to add water we must lose ether F or A. So let’s add some water.
If C = 20v And A = 15 And F = 3 And W=2
Then
C = 20

Now we have depleted fuel 2. Our AR is staying same because we are running a boost number to sustain its operating volume.

Adding spark can only help to surpass its natural flame deterrent water. Now yes we can tune A down as well as F and W but doing so we still must sustain a proper AF ratio. Where as with methanol or alcohol you replace our combustion fluid "fuel" with one of another type. This no longer retards the spark properties nor does it decrease your value of F.

Now I understand water changes properties. But we must see what the reaction is on paper. The principal none the less stays the same.

Now without a properly tunable EMS we have no control over F. This will yield us running lower A ratio rather then F. Where W will dilutes F to become in operational, if the level of A is retard to where F can no longer undergo proper combustion we begin to run rich. This will calculate a large drop in HP. If W surpass AF we begin to see misfire.

 

Now keep this in mind. I am really not trying to convince you of anything. I am merely putting the information out there, because I get tons of questions regarding my injection setup. What you choose to do with the information that I have provided is entirely up to you. Furthermore, whatever case you make for water (although wont convince me), may convince someone else. In addition ANY pertinent information added to this thread is of value to the community as a whole.

I am a stolid proponent of alcohol, and you are a proponent of water. We both think we are right, but either way, there is ALOT of good info being presented here in (unbelievably enough), a calm and rational manner.

Rat

 

Ah, my friend, you have made the serious mistake of not understanding basic physics or fluid dynamics (which doesn't apply in this case), then assuming I don't understand (which I do), then pretending that you do understand in an attempt to intimidate/strongarm me.

Ok, this seems logical so far. Add up the volume of everything in the chamber and it is the total volume.

Your mistake. Here the problem with your equation and perhaps your understanding is exposed. The correct measurement of how much air, fuel, and water we actually have would be by mass/moles. The reason you are able to substitute volume for fuel and water is because they are liquids and they have a set density. Air, however, is a gas. You can approxiamate it using the ideal gas law pV = nRT. So when we add water, we decrease the volume of air and therefore increase temperature and pressure. The fuel doesn't magically disappear anywhere. Of course, the amount of water added is such a trivial amount volume-wise that the increase in temperature and pressure in air is almost nothing.

Your AFR would stay the same if you decreased boost, otherwise you would start running more lean.
Um, no need to tune down A and F and W.

A car that runs on just methanol consumes twice as much by volume as a car that runs on just fuel. Not sure, but I think I can then say that you would need twice as much methanol to match the combustion properties of fuel.

The reactions are the following 3:

OH + H ==> H2O
H2O + O ==> H2O2
H2O2 ==> OH + OH
Loop to top and repeat.

OO + H ==> HOO
HOO + H ==> H2O2
H2O2 ==> OH + OH

CO + OH ==> CO2 + H
H + OH ==> H20
H2O + O ==> H2O2
H2O2 ==> OH + OH
goto to top and repeat.

The last one is responsible for approxiamately 2/3 of the energy in combustion. Excess water (that is, water from water injection) will speed up this conversion.

I think you know what I'm going to say...

 

I like to see myself as calm and rational. This thread certainly has forced me to re-research and rethink some of the ideas I held regarding water injection. I would like to thank you for being so calm and rational yourself.

I still think water injection is better, though I now believe that methanol is able to reach much higher limits (that is, running only on methanol) of compression than water injection. (limited to power increase of 50% as researched by NACA) However, having to inject twice as much methanol by volume to achieve the same effect as water, especially when you consider high costs of methanol and free costs of water, water wins handsdown.

Methanol certainly is able to match cooling factor just by injecting more and will depend on just cooling to achieve non-knockness at high boost, but I'm still not absolutely sure there aren't other effects that water is able to achieve that no amount of methanol can create.

Also, I was wondering how methanol matches up vs. gasoline as a fuel, since running methanol injection necessitates reducing the gasoline (replacing it with methanol) so as to maintain optimal air-fuel ratio. Meh. It probably makes little difference. Gar, my head hurts. Cars are too much work. I'm going back to computability theory.

 

Well thx for the reply gingenhagen, nothing is to strong-arm you. However all is to do with communicating theory and advancing knowledge on the subject. Simply posting a paper theory on the subject using common laws. Now let me see if I can communicate back with you some.



The above expression is that of injection taking place of fuel. As in a tunable system. Further down I typed in a non equation format in a non tunable system that F would stay at 5 and A would decrease the amount of W.

Please correct me if I am wrong here. But your ^ gives me the impression that you are correcting the W vs. F and not the property of the equation. If this is so maybe I am just misunderstanding your conclusion of the equation but with the proper equation of A - W I do not see that you are disagreeing with my equation. Here is an A - W expression.

If C = 20v And A = 10 And F = 5 And W=5
Then
C = 20

If A is metered or calculated then F is distributed accordingly. If A is subtracted to compensate for W then you run rich. Right? That is what I have been saying.

 

Don't forget there's also the cooling effect, which thus makes the air more dense, which allows some of the ability to have water displace more, but still having more air (density speaking)