Hum… and the whole time I was writing that response I kept thinking that “I should check to make sure that conversion is right… but of course it’s right” and kept trying to explain the slight difference. (I call it persistence, the wife refers to it as stubbornness)

WRT to the recent discussion, if we’re to believe Ricardo’s experiments, charts and conclusions, that’s not what’s happening, but that the water is replacing amount of extra fuel that you’d have to add to keep the engine out of detonation so you’re not displacing any air fuel mixture. I’d be very surprised if all of that water was actually vaporizing prior to entering the combustion chamber (but like I said, I don’t really believe the major advantage to water injection being as much the cooling as it’s effects on detonation in the combustion chamber)

It would be interesting to see if you took the 20% alcohol setup added half that much fuel and just injected the water (in other words, if it was 125Lb/hr of the water/alcohol, if you just injected 100lb/hr straight water and added about 12.5lb/hr fuel) to see if you got the same power, I’d guess that you would (in other words, the reason that 20% works best is that the engine really wants a little more fuel when injecting the water, probably due to the cooling).

WRT to

Methanol on the other hand increases O2 mass and O2 % content in the cylinder

as far as I know that’s pretty much a myth. Yes, methanol has O atoms as part of it, but they are already effectively oxidized (combined with other atoms), so there is no substantial power to be gained from them, they are essentially just along for the ride (though I haven’t sat down to try to figure out if they are actually recombined in a lower energy state after combustion so I could be wrong).

 

"I don’t really believe the major advantage to water injection being as much the cooling as it’s effects on detonation in the combustion chamber"

I hardly think you can exclude one for sake of the other chap... they go hand in hand. What happens to imep is another matter you might want to look into for the "power increase" side of this whole debate. The cooling effect in-cylinder is significant. Best power will however require a bit of experimentation. You're looking for the best water/fuel ratio and that has an effect on quite a few things, specific fuel consumption being one, if that is a concern.

We've been using water/methanol injection for about twelve years now in our drag bike race engines and some of the hill climbers. So we've been around the pond with it a few times. Not for the novice to jolly around with.

Gooday,
Mike

 

I'm sorry if I gave the impression that I was excluding water's effect of cooling (I thought I wasn't, I was even suggesting that some of what you were seing was the result of the cooling at the end of the message that you quoted part of), my point was that it's effect as an anti detonant appears to be stronger then it's cooling effects (I say effects because we're not only talking cooler intake charge, but cooler exhaust...).

And yes, I also agree that one of the more interesting effects (if it matters to you) is that if a sufficient ammount is used it lowers BSFC of the engine to what it would be if it was not boosted.

 

I read in my turbo charger book the other night after I read this post and read that steam is a good anti detonant, still not sure why. I'm guessing because it will can absorb a lot of energy.

I'm not sure if you can say that methanol won't add to the oxygen because it has been oxidized. The oxygen in Nitrous is combined with other atoms but it obviously adds oxygen to the process.

 

You can't compare the O2 enrichment via nitrous to the methanol issue. It is clear that at high temperatures, N2O breaks down into elemental oxygen and nitrogen... no question that is alters the % O2 content in the combustion chamber, and takes part in the combustion process, generating heat and increasing the burn speed.

As WS6 TA points out, the oxygen in methanol is combined in the hydroxyl radical (OH). The question is whether this oxygen is available for combustion. Remember, water has a lot of oxygen in it, but it does not take part in the combustion process because it stays combined with the hydrogen.

If you look at the stoichiometry of methanol:

2 CH3OH + 3 O2 -> 2 CO2 + 4 H2O

In effect, the hydroxyl radical appears to combine with some of the hydrogen, so it isn't a total loss??????

Looking through some reference material, it is obvious that methanol does not accelerate flame speed via O2 enrichment, since the references all relate methanol to a "slower-burning fuel". So much for that theory.

The same reference cites the advantages of methanol as the obvious cooling of the intake charge, but then goes on to note that for methanol fueled engines, combustion temperatures are typically 100-150degF lower than gasoline fueled engines.

There is a lot of interesting info in the Motorbooks International soft-cover "High Performance Automotive Fuels & Fluids", by Jeff Hartman. ISBN 0-7603-0054-2

And look at this link:

GASOLINE FAQ

 

The nitrogen and oxygen separate?
Learn something new everyday.

 

Thanks Injuneer for putting what I was trying to say in technically correct terminology (at times I seem to have no desire to do that myself, even though I’m sure I read/know enough about it to do so, with chemistry it might be the run ins that I had with the chemistry dean while in college… I have a similar aversion towards electronics… Might be just my belief that “if you can’t say it in your own words without resorting to overly technical terms you don’t understand it.” Of course, that backfires because most that understand what you’re getting at look at you funny when you don’t phrase it the right way, oh well…)

Anyway, it looks to me that that O is a total loss, the hydroxyl’s just combine with the leftover H and you get H2O, it never gets used to oxidize anything (yea, overly simplistic…)

The burn rate is dependant on the fuel, combustion conditions… I don’t believe that if that O was being used to oxidize it would necessarily have a faster or slower burn rate.

I’d add to that that in the case of using it as a fuel you make up for it’s lower latent heat by using at a minimum 3x as much as you would water if you were using water injection and gas, so of course you’re going to have a nice cooling effect. In some cases much more, remember that methanol makes best power at around 4.3:1, where gas makes best power at around 12.5:1, and this is assuming that you were injecting almost as much water as you were gas with the water injection setup, if you weren’t injecting at nearly that rate then you’ll get a substantially greater rate of cooling then that.

 

But is H + OH -> H2O an exothermic reaction?

I really don't know.....

 

Don't look at me... when I was a freshman in college I had enough run ins with the Dean of the Chemistry dept that at the end of the semester I was told "you will never take another chemistry class at this university...."

I'm not the one to ask about chemistry. Loud noises and flames interest me enough that I've been found to be incompatible with a chemistry lab

 

This is a great thread guys and im learning a hell of a lot from all this. I Have bought anSMC alky injection kit for my blown application so this applies to me directly. I was under the impression that water/alky mix lowered your iat's and by lowering the iat's it reduced your chances of detonation right?. I am in no way as advanced in all this as you guys are so bare with me. I was considering using just dentared alky for my setup but from what you guys are saying is that I should run a mix with water to get best gains right?

 

I don't remeber too much chem, but I do know it takes as much energy to break the H-OH bond as you get back when they recombine. Something about conservation of energy sticks in my mind....

Rich Krause

 

Interesting thread.
fwiw, I run a 3 nozzle system of my own design on my supercharged ls1 TA.
Delivery pressure is 120psi. I run from 16-20gph with a 50%-(40%/10%) mix of water/methanol/acetone.
I use triple nozzles and high pressure for good atomization.

NO intercooler and 12psi boost, around 700 crank Hp. IAT runs about 20' over ambient with the system activated or about a 100 degree drop as monitored.
I run the motor at a shown 11.2 A-F on in car wideband or more accurately a .762 lambda.

I use teflon lines,brass fittings and anodized aluminum dist block.
Corrosion is not a problem with these parts.

Plug gap needed to be closed to .028" to prevent high rpm misfire.
The system keeps the motor nice and clean of carbon, allows pump gas to be used, is a very effective anti detonant , cools the intake charge to allow a lot more timing and shows a very little coolant temp rise after a full pass.
If done right, these systems are very effective IMO.

Steve

 

Hey Steve, what pump are you using to get that kind of pressure and volume? What nossles are you using? Any pics?

 

I am using a 1.4 gpm shurflo pump.
I bypass the pumps auto pressure switch and control pump pressure with a return style system, like most efi fuel systems.
I run the pump with a return line and use a bleed jet in the return line to regulate the pressure. A .038 jet is used with this nozzle combo for 120psi.
So pressure/flow changes are easy to make with a simple jet change.
I am using three 5gph(rated at 100psi) McMaster mini atomizing nozzles.
At 120psi the 3 nozzles flow 10.5 oz in 15 secs for a 19.7 total gph and atomize quite well.

I don't have any pics though.
Steve