Liquid or vapor Meth for power enhancement?

[masterp2]

There are choices/concessions in deciding on atomization and degree of vaporization. The question is this:

Which is better for HP improvement when implementing water/meth WI with a low humidity ambient condition? 100% saturation or small droplets?

Guess we should not forget (if I am correct) that humidity will not effect how much meth will be vaporized. With respect to meth, ambient air always has 0% vapor pressure of meth. So even a 100% (rainstorm) humid environment can still be cooled and power enhanced?????

[masterp2]

Help please. I am quite puzzled. From the turboICE article

http://www.aquamist.co.uk/info/documents/turbowhitepaper/waterinjection.htm

There is a part of this article that I find disturbing, mostly because it confuses me in defining the goal of WI. Is it to evaporate a water/meth mix or not? The article almost justifies, boasts the systems poor evaporation efficiency.

Quoting:

The injection of water into the induction charge will immediately absorb heat from the charge thereby increasing its density. Evaporation of the water at this point is unlikely or very minor. The induction charge can at a maximum reach 100% relative humidity and will stabilize at an equilibrium state that is governed by temperature of the charge exiting the turbo and the relative humidity of the ambient air. At full saturation the induction charge will have a significantly reduced temperature somewhere between the ambient temperature and the temperature of the injected water.

Aquamist promotes a low pressure (100psi) system that outputs avg 50-80 micron droplets (guess), not the best way to evaporate water. So the statement may be correct, but I am confused. Are they trying NOT to evaporate until the intake valve? Because if you want to evaporate (and cool) more, simply get higher pressure behind a smaller nozzle, preston 10 micron fog, flash evaporation. So see I am confused. Cleary evaporative cooling can bring temps below ambient, even using hot water. We do it hear in outdoor mist settup all the time.

To evaporate, or not to evaporate?

[hotrod]

I think one of the issues here is simply a choice of word usage. Most of the discussions on this topic throw around general terms like " an insignificant amount of water is evaporated" --- what I consider insignificant someone else might consider to be quite large or vise versa.

As you know from the water fog cooling systems used in the desert SW, even in high temps, brutally low relative humidities and high temperatures it takes a signifiant amount of time to evaporate a water mist completely. In the NACA studies even in cases where the water mist passed through a turbocharger compressor, only a fraction of the water was evaporated, and dropplets were present down stream from the compressor..

My personal preference is to go for maximum evaporation. Your never going to get it, but there are several hints out in the NACA studies and in other sources that applications that do not give the water mist ample travel time to mix and evaporate do not achieve as much max power potential as systems that place the nozzles well back from the throttle.

No matter what you do, a lot of the water will arrive in the cylinder as small dropplets. If for no other reason than to minimize variations in water transported to the various cylinders, I think the mist size should be as fine as practical. In the real world it is difficult to get mists smaller than about 50 micron at reasonal pressures and without having nozzles that are prone to clogging. For that reason alone the 50 micron dropplet range is probably about as good as your going to get in a practical system.

If you get dropplets much larger than the 80 micron range then you get into problems with the water getting centrifuged out of the air stream as it transits the intake manifold. I believe that is why that target range is frequently mentioned.

Larry

[masterp2]

Insightful!

Clogging issue aside, I wonder if higher pressure systems lack the price tag for popularity, being what keeps them at bay? Little extra benefit for the extra evap, hmmm.

Those afraid of pre-turbo misting usually have a coarse spray. From what I read, 100 psi misting has a fair amount of larger drops over 100u, and some reporting of long term compresssor damage. With fine misting it is a non-issue.

What is concrete to me is that evaporation can be easily quadrupled (assuming the statement above is correct) in our dry air with a little PSI effort. BTW, we like the dry air, no mosquitos, and when I go bike riding in 115 F heat, I carry my AC on my back, 2 gallons of H2O.

Yes I see now how liquid is important at cylinder entry (especially with our 1200 F EGT temps). Some quick evaporation and cooldown there=charge density. Seems the effort is well served to make the dry air saturated before it gets there, especially when meth is used to enhance performance. The vapor of meth being more of an enhancement than liquid (which does not combust).

[1QuickBunny]

<<<I wonder if higher pressure systems lack the price tag for popularity, being what keeps them at bay?>>>

I think it is an issue of price. Higher pressure systems are damn expensive. I have spent over $1500 on mine and its not even realy complex, just a 2s with a few extras. You see stuff on E-bay for as low as $60-100... most people won't start off with an expensive system when soo many of the "performance handbooks" say to stay away from wi and call it a bandaid approach... Only in the past year or so have I seen the mainstream tuners take an open approach to wi!