Water/Meth What does it really do ?

Troy · Jul 14, 2015

Hello all, lots of talk about water/meth and what it does to help some combinations. Would love to hear what the "pros" have to say about it. I have been thinking about doing a in-depth conversation/post about what it does for awhile now, why it works and who needs it but it would be a long winded post especially if it is already common knowledge. Really interested in hearing/learning from someone who may have seen it in oem applications or someone with in-depth knowledge of oem's and emissions knowledge.

I have read/tested a lot over the last few years, reducing air intake temperature is NOT where water/meth is of benefit. Its what it does in the chamber that matters, so far I have been totally unsuccessful at finding real data/information. Even manufactures of "water/meth kits" don't really explain why it works or maybe they just don't want to go into detail ? FYI, I do not sell water meth kits, just a obsessed hot rodder with a lot of emissions, oem repair experience

Troy Clark

Forcefed86 · Jul 15, 2015

Water inj. and Meth inj. are really two different topics. Each with it's own advantages.

It’s main benefit is lowering CC temps and/or upping octane (slowing burn). This allows you to run more cylinder pressure without detonation.

Lots of good info out there with WWII test data on the radial engines. Here is one..

http://enginehistory.org/Frank WalkerWeb1.pdf

Lots of info from these guys as well

http://www.riceracing.com.au/water-injection.htm

Also has some small chemical advantages discussed below...

taken from another thread by bill shurvington(ausrotary)

K Stage 1

Intro: This has been covered before, but just to set the scene. Water is NOT passive in combustion, it aids the

conversion of CO to CO2, which is where most of the energy of combustion is released. It also helps cool

things down( in the process reducing the work done in the compression stroke) and prevents detonation.

You can replace a significant amount of the fuel with water allowing you to run at the best power AFR rather

than running overly rich and losing power. Disclaimer: I give not a stuff what is said on WI equipment vendors websites, so if I disagree with aquamist so be it. They are a pump manufacturer.

Pre-turbo WI: Compression in a turbo is usually adiabatic. This means that the air is heated as it is

compressed, which takes power from the shaft and requires removing through an intercooler. If you inject

water before the turbo, then you can move compression to near isothermal, so very little heat is added, and

less power is taken from the turbine to compress the air for the same boost level. You can loose the

intercooler and therefore suffer less pressure drop between compressor and inlet. All of which gives you the possibility to get more power out the same turbo.

Water has a very high latent heat of vapourisation, but once you have reached the saturation pressure in air, then you gain no more cooling at that point. However Dalton's law comes to the rescue at this point and if you bung in some other miscible fluids, say methanol and acetone, then each has its own saturation pressure, and you get an accumulative cooling effect. A little petrol would do the job if you added a second injector for it.

And here we hit the first problem. You need fine atomisation to avoid potential blade damage. For this you need an airshrouded injector, such as VW used in some of their CIS systems (hunting applications list for those). RX7s have an airpump that can be turned to this application. Other option is to weld a bung into the scroll as most of the compression happens here.

I need to run some numbers on exactly the effect of various fluids here, but imagine if you had cut the power needed to get the PSI wanted by a 1/3. You would get spool up at 2/3 of the gas flow before and could run at higher boost once you had spooled.

Post turbo WI: Here you are adding water to deal with combustion and detonation reduction. Ideally you would inject directly into the chambers to minimise any charge displacement. The OMP drilling in the housing would work nicely for this if you run premix. In terms of sizing you would be wanting to replace about 30% of the fuel with water, so size accordingly.

Quick note on A/R changes with WI: If you inject water directly into the exhaust, then it rapidly expands and turns to steam. In doing so it takes heat out of the exhasust, but the volume gain more than makes up for this. Tricky to implement, but can be used to change the effective A/R of the turbine, giving you a much wider operating range. MSD do a system for 2 strokes that uses this effect to change the effective tuned length of the exhaust to improve scavenging.

That's me out of time for now, but have a think and ask some questions. Remember, if you say 'but Mazda/aquamist/the lad with a supra on my block don't do it this way' I shall laugh maniacally and point you to the work of Sir Harry Ricardo on the rolls royce merlin engine in the late 30's. He was a genius.

Part 2b: water is good for your bang

below is a great mail written by Bob Harris a few years back explaining, in far more lucid prose than I could ever hope for. Key points to note in the text:

1. Water speeds up the key reactions releasing energy to the crank in a sharper peak. This means more power at the wheels. Note the comment that 2/3 of the energy released in combustion comes late in the cycle without water present at the beginning. This is less of a problem in a rotary than a piston, but you still lose leverage on the eccentric (note I haven't looked at it from a heat lost to the rotor perspective).

2. Water injection has been shown to give very significant increases in max power

3. At >35% WI it has been shown you can run under boost all the way back to stoich without detonation in piston engines. No reason a rotary shouldn't be similar. Extrapolating this you can see that you can also run more advance (more power) and also use AFR to control power output, rather than run stupidly rich just to prevent engine death, or backing off the spark so you loose lots of the HP you paid for.

Quote:

Let us take a quick look at ignition. Those who have a Heywood can look it up
- mines on loan so going by memory. The first thing that happens is a plasma
cloud is formed by the arc consisting of super heated electron stripped atoms.
When this cloud "explodes" a ball of high energy particles is shot outward.

The highest energy particles are the hydrogen atoms - and they penetrate the
charge about 5 times as far as the rest of the particles. As they lose energy
and return to normal temps - about 5000 k - they begin to react chemically
with any surrounding fuel and oxygen particles. The effectiveness of spark
ignition is directly related to the availability of free hydrogen. Molecules
containing tightly bound hydrogen such as methanol, nitromethane, and methane
are far more difficult to ignite than those with less bonds.

During combustion - water - H2O ( present and formed ) is extremely active in
the oxidation of the hydrocarbon. The predominate reaction is the following:

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

The OH radical is the most effective at stripping hydrogen from the HC
molecule in most ranges of combustion temperature.

Another predominate process is the HOO radical. It is more active at lower
temperatures and is competitive with the H2O2 at higher temps.

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

This mechanism is very active at both stripping hydrogen from the HC and for
getting O2 into usable combustion reactions.

Next consider the combustion of CO. Virtually no C ==> CO2. Its a two step
process. C+O ==> CO. CO virtually drops out of early mid combustion as the O
H reactions are significantly faster and effectively compete for the available
oxygen.

Then consider that pure CO and pure O2 burns very slowly if at all. Virtually
the only mechanism to complete the oxidization ( Glassman - Combustion Third
Edition ) of CO ==> CO2 is the "water method".

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

This simple reaction accounts for 99% + of the conversion of CO to CO2. It is
important in that fully two thirds of the energy of carbon combustion is
released in the CO ==> CO2 process and that this process occurs slow and late
in the combustion of the fuel. Excess water can and does speed this
conversion - by actively entering into the conversion process thru the above
mechanism.

The peak flame temperature is determined by three factors alone - the energy
present and released, the total atomic mass, and the atomic ratio - commonly
called CHON for Carbon, Hydrogen, Oxygen, and Nitrogen. The chemical
reactions in combustion leading to peak temperature are supremely indifferent
to pressure. The temperatures and rates of normal IC combustion are
sufficient to cause most of the fuel and water present to be dissociated and
enter into the flame.

As can be seen above, water is most definitily not only not inert but is a
very active and important player in the combustion of hydrocarbon fuel.
Ricardo and others have documented that under certain conditions ( normally
supercharged ) water can replace fuel up to about 50% and develop the same
power output, or that the power output can be increased by up to 50% addition
of water. This conditions were investigated by NACA and others for piston
aircraft engines. It is important to note that these improvements came at the
upper end of the power range where sufficient fuel and air was available to
have an excess of energy that could not be converted to usable pressure in a
timely manner.

As a side note - Volvo recently released some SAE papers documenting the use
of cooled EGR to both reduce detonation and return to a stoic mixture under
boost in the 15 psi range - while maintaining approximately the same power
output. Notice - they reduced fuel and still get the same power output.

When you consider that EGR consists primarily of nitrogen, CO2, and water ( to
the tune of about two gallons formed from each gallon of water burned ), you
might draw the conclusion that it also was not "inert". They peaked their
tests at about 18% cooled EGR - which would work out to about 36% water
injection and got about the same results under similar conditions that the
early NACA research got.

Click to expand...

Troy · Jul 15, 2015

Thank you Forcefed86, But....that is what I am looking to expand on, I like the explanation given but I feel there is more to it than that. I have a "new" theory at least one I have not read about it anywhere and I have looked a lot !

The topic of EGR valves talked about above is HUGELY important. The true purpose of an EGR system is to reduce combustion chamber heat by recirculating already burned air/fuel(for the most part inert gasses) When this happens Oxides of Nitrogen are reduced commonly referred to as NOx and often mistaken as NOS. It is important to understand The Oxide part of oxides of nitrogen, Just like Nitrous is an "oxidizer" I.E. it does not support combustion on its own but when mixed with a fuel source it does. My theory is that "oxides of nitrogen" are a hot roders worst enemy, understanding it and how to control it will be the next "evolution" in tuning much like the wide band oxygen sensor has been...Interestingly enough the wide band o2 can not function accurately in a high NOx environment, it was not until variable cam timing(think early evo) and advanced electronics did OEM'S finally gain control over NOx production and the wide band O2 output could be trusted.

In simple terms, we fight heat, not just due to it thermally changing the shape of or engine components but due to the fact extreme heat in the combustion chamber will cause the formation of Oxides of nitrogen and Oxides of nitrogen will cause rapid engine failure in high enough concentrations, most notably in the form of pistons with a hole in the sides of them. Why the sides or ring land area of the piston ? The sides, in the ring land area is where raw fuel/hydrocarbons are trapped(fuel source) and when combined with an oxidizer(NOx) and a ignition source(piston ring scraping/friction on the cylinder wall) you get a flame that cant be stopped until the fuel source is used up. That is my take on it anyway

There are to many variables to list all the things that may cause a high Nox environment, spark plug heat range, chamber shape, coolant temp, bore size, ring tension, ring thickness, oil weight, ignition timing, cam timing , power adder of choice, intake/exhaust manifold systems, fuel type and so on. Basically anything that make's heat can contribute to the production of NOx.

I feel this is where water injection or methanol injection or any combination of it shines. Its real benefit comes from the reduction of NOx in the combustion chamber. While reducing air intake temp is helpful it does not tell much of the story, most of the heat happens in the chamber. The wide range of contributors to a high NOx environment also explain why some combinations benefit from water/meth or combo's of better than others.

Forcefed86 · Jul 16, 2015

Assuming we are strictly talking about turbo engines here…

I believe the main concern is fighting rapid spikes in cylinder pressure. (which is of course related to many things, NOX included I'm sure) If NOX levels are impacted heavily by heat, then it’s safe to say reducing heat will reduce NOX. So by reducing heat or anything that contributes to heat will reduce cyl. pressure spike tendencies. (AKA pre-ignition detonation.)

It would be great to know what kind of weight (percentage wise) reduced NOX in the CC would provide. As well as how close a relationship overall heat plays on NOX levels. If NOX levels rise linearly with heat, is there really any discernible difference between the two? Is there an effective way to reduce one without reducing the other? I’d guess an EGR valve would be a good example of reducing one without the other? Yet we don’t see EGR valves used in the performance world because…?

Strictly from a performance view point I don’t believe NOX has as much of an impact as you think. IMO putting spent emissions gasses back into the CC isn’t a recipe for increased performance in a turbo engine. You are taking up space that could otherwise be used for “fresh” air/fuel.

I agree AUX injection has little effect on overall air charge temps, and the majority of the gains take place in the CC. However I believe this is mainly due to a drop in CC temps and a slowing burn rate. I also believe unless you have a ARC welder for an ignition system, straight Meth will always make more power than water or and mixture 10,20,30,50/50 etc. Whether it’s needed or worth the extra trouble to run 100% meth it is application specific.

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Water/Meth What does it really do ?

Troy

Forcefed86

Troy

Forcefed86

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