Man, this is a topic that bothers me, mostly because of the extreme amount of misinformation out there.

Some quick facts:
Heat of vaporization for:
Water: 2.26KJ/g (about 20x that of gas if I remember right)
Methanol: 1.17KJ/g

In simpler terms, water absorbs roughly 2x the heat that methanol does when it vaporizes.

Now all you boosted guys out there… you know roughly how much air your engines ingest and now you know how much heat both will remove… figure out how much water you’ll need to inject to cool down your intake charge.

I’ll give you a hint. I worked this out for my brother’s Eaton M90 Blown Ford 5.0… to drop his inlet temp by 80 degrees at WOT he’d have to inject water at a rate of roughly 160Lb/Hour… MUCH MORE then any water/alky injection setup does, hell, that’s more water then amount of fuel most of the V8’s that we’re messing with were feed at WOT stock. (BTW, we did test this empirically on that car, using a real pump capable of delivering up to about 130 psi, and injectors triggered by the Haltech engine management that that car uses. We tried more typical rates that other water injection systems use, up to about 35Lb/hour water (well, that's what the injector flow bench showed), with data logs and track times, we didn’t see a temperature drop that we were sure was being cause by it, but we did see 3-4*F less in the intake)

So if you’re injecting water to cool your intake charge… Well, look elsewhere for that, by the time you put enough water in the engine to get a substantial effect it won’t run (and yea, I know that there are some fairly dramatic #’s floating around the ‘net, how much do you want to be that the water mist was hitting the upstream temp sensor and cooling it more then the air?). And, if that’s your goal, and you can’t get it with water why would you use methanol which will have to be injected at 2x the rate to get the same effect???

What it is effective at is as an anti detonant. If you want information about this look for Sir Henry Ricardo’s book from the 1930’s, he studied this quite a bit and even graphed out the results on a fairly well published graph. He basically found that water injected into the cylinder had a dramatic effect (much greater then adding fuel or increasing octane) on preventing detonation.

That being the case, why would you want to dilute that effect by adding methanol (or other alcohol) which is just a fuel with slightly higher octane?

There’s only 3 reasons to add an alcohol to the mix (well, there may be more but these are the ones that I can think of):
1) if your fuel system sucks and you cannot deliver enough fuel for the air you’re moving (remember, methanol makes the most power at an A/F about 4:1 so if this is what you’re doing you’ll need to add A LOT of it)
2) to keep the water from freezing in the winter (then just use the minimum that you need)
3) or if you don’t really know what you’re doing, misinformed or just haven’t thought about it much (sorry, couldn’t resist), “Dude… it will make it go fast…”

 

Agreed.

Quote:

Now all you boosted guys out there… you know roughly how much air your engines ingest and now you know how much heat both will remove… figure out how much water you’ll need to inject to cool down your intake charge.

I’ll give you a hint. I worked this out for my brother’s Eaton M90 Blown Ford 5.0… to drop his inlet temp by 80 degrees at WOT he’d have to inject water at a rate of roughly 160Lb/Hour… MUCH MORE then any water/alky injection setup does, hell, that’s more water then amount of fuel most of the V8’s that we’re messing with were feed at WOT stock. (BTW, we did test this empirically on that car, using a real pump capable of delivering up to about 130 psi, and injectors triggered by the Haltech engine management that that car uses. We tried more typical rates that other water injection systems use, up to about 35Lb/hour water (well, that's what the injector flow bench showed), with data logs and track times, we didn’t see a temperature drop that we were sure was being cause by it, but we did see 3-4*F less in the intake)

So if you’re injecting water to cool your intake charge… Well, look elsewhere for that, by the time you put enough water in the engine to get a substantial effect it won’t run (and yea, I know that there are some fairly dramatic #’s floating around the ‘net, how much do you want to be that the water mist was hitting the upstream temp sensor and cooling it more then the air?). And, if that’s your goal, and you can’t get it with water why would you use methanol which will have to be injected at 2x the rate to get the same effect???

I seem to remember reading somewhere, something quite to the contrary.
I believe the calcs I saw were assuming 100% VE, a given port air consumption per cycle, a given fuel consumption per cycle and an equal amount of water/methanol injected per cycle. The temperature drop from voporization was in the 150*C region. I might do a refresher and run the calcs myself since I'm curious now.
I'd say that thats a significant cooling effect and that can be useful whichever way you choose to use it..... extreme compression n/a, force inducted, whatever.

There are a few guys using water/meth around here for various purposes and they seem to be having some luck with the stuff. Always more than one opinion right.

-Mindgame

 

Run the #’s, I’d love to get a 3rd person in on this, since it’s always possible that we missed something.

I originally ran the #’s and didn’t believe them, went over to my dad’s house (engineer for 50some years, used to do HVAC and temp management for steel plants and before that worked on the engines in the Apollo booster rockets and LEM engines, so knows something about heat/cooling, fluid flow…) and just told him that I’ve got air at this pressure and temp, how much water do you need to drop the temp X and let him at it… He came back with a slightly different # then I did but after looking over what he did we found that he forgot to convert pressure ratio to density ratio and when he did he ended up with the same #.

I still didn’t believe it (again, didn’t match what the numbers that most people claim) so we actually built the setup to tested on the boosted engine in my brother’s car and like I said, if there was a cooling effect we couldn’t accurately measure it, and we were set up so that we could turn the system on and off, change the triggered pressure and even the amount using a laptop while driving, datalogging the whole way (didn’t have any detonation before or after so that wasn’t an issue).

 

Let me do a bit of referencing here and I'll get back with ya. These aren't the type of calcs I do on a daily basis so I'll have to get my stuff in order before running my mouth.

I'll be back....

-Mindgame

 

Take your time, I’d rather have it right then fast. And I’m not giving you hints so you don’t just work the same #’s that I did and get the same answer (believe it or not this is stuff that I play with on my free time…)

My wife is a reference librarian (possibly soon running the library for the enemy, the EPA), so if I don’t know something, I cheat, I just call her and get her to find it

 

Do you want to use the Meth as a replacement for N2O, as a supplement for N2O or boost, or just use it by itself?

Will your meth injection (should you choose to do it) be constantly on, or will you turn it on and off for more power (like N2O)?

 

I inject 15gph of water, which is = to ~90lb/h. The IATs are in the 130-140 degree range after a 1/4 mile run on a 70-75 degree day with 14psi of boost. Without the water it's up around 200 degrees. So whatever your calculations show, I believe water works.

Rich Krause

 

Rich, that almost follows what I was saying that the #’s suggest. You’re saying that you’re getting about 60* drop with about 90Lb/hr water (If you fudge it a little like you didn’t quite get 60* or you’re getting a little more water it gets closer). Like I mentioned earlier, calculating it out on the application that I was going to test suggested that I’d need 160Lb/hour to get 80* (you know, it might have been 100*, If I have some time I’ll have to sit down and look at it again, I’m not sure why I would have originally chosen 80*).

Do you have details of your engine and water injection system posted somewhere (or can you)? How do you know that you’re getting 90lb/hr? It would also be interesting to know if anyone has run enough water through an engine under boost that they were getting significant white smoke or some line where it made things worse, rather then better.

I don’t think that I was suggesting that it doesn’t work (the reason that I spent time thinking about it is that I do think it’s useful for some applications that I will eventually be running), but more that you need a lot more then most people run (I’ve seen setups that deliver 1/10th the water that you’re using), that the anti-detonant qualities are more important then the cooling, and it doesn’t make sense to run any more alcohol mixed with it then you absolutely have to (if any).

 

It seems we are on the same page in many respects. I have measured the output at ~15gph, the actual amount delivered is somewhat less than 15gph I mentioned, because I measured into a bucket, not against 14psi (max) boost. A while back I gave up arguing with people over water v. alcohol v. a mixture. I use 75-80% water and 20-25% methanol based on trial and error, it seems to work best. The volume of water is empirical, I test on the dyno and look for (obviously) max hp. What works best is typically one jet size less than the amount which causes the motor to "lay down", which is immediately apparent from the way it runs. So you don't really need a dyno to tune water, just a bunch if different jets.

I agree that many of the systems are ridiculous. There is no way they can deliver enough water to be worthwhile and the pressure is too low to properly atomize the water. From work on the dyno though, I know that water makes hp when done properly. On last years setup it was worth ~30rwhp.

No web details for my setup, but it's Carroll's system, expensive but well thought out. My friend Bob Kennedy makes a functional system that's less elaborate than Carroll's. There is info at www.kennedysdynotune.com if you are interested. Last years setup was a basic 383 blower car with a small cam (214/224) and a Vortech S-trim. With very mediocre heads (out of the box AFR's) and a low (8.5:1) DCR it made 613rwhp on race gas and 597rwhp on pump unleaded.

Rich Krause

 

15GPH water = 125#/HR

 

Ooops, you're right, I was thinking of gasoline.

Rich Krause

 

Glad I could make a major tech contribution to the thread.... .

 

I was wondering what airflow rate you were using to calculate this temperature drop/amount of water needed?

It also seems that this might be a little more complicated then how it is calculated. It looks like your assuming that all of your water injected is going to be vaporized. Since your temperatures are below boiling (sometimes) and your pressure is elevated, then the amount of water to vaporize will depend on how much water vapor the air can hold. The rest will simply condense. Or did you account for this?

This is the only cooling advantage that I can think of where methanol might have an advantage over water. It might vaporize more readily with the incoming air.

Oh one other question, what gives water an anti -detonant properties? The only thing I can think of is it will cool the incoming gases/combustion chamber.

 

Now it would seem we are getting to the key differences between water and methanol. Heat of vaporization seems important at first, but the amount vaporized is important, and what happens to it AFTER it vaporizes is night and day. The water will displace air/fuel mixture, reducing O2 mass and % content. That slows combustion and reduces combustion chamber temperatures. Methanol on the other hand increases O2 mass and O2 % content in the cylinder. One displaces power producing combustion components, the other increases the power producing components.

Not sure what all this means... but it would seem to be a little more complex than looking at the heat of vaporization of the "diluent" and the specific heat x delta T of the air.

 

That may help to explain why an 80-20 mix showed the best results per rich. Could the 20% of Methonal help to negate the dilutive effect of water?