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5mall5nail5 16-03-2012 06:21 PM

Looking for a Water:Meth ratio vs cooling chart
 
I used to have this saved somewhere. Discussing with a friend and I want to show him. It was a chart showing, I believe, the cooling effects of different ratios of water:methanol.

Anyone know of/remember that chart?

Thanks,
Jon

Richard L 22-03-2012 09:49 AM

Re: Looking for a Water:Meth ratio vs cooling chart
 
The following charts are calculated based on:

10Kg of air, Gasoline's latent heat capacity of 350KJ/Kg
Water's latent heat capacity of 2256KJ/Kg
Methanol's latent heat capacity of 1109KJ/Kg

Injection water at different ratio to fuel at 100% water and 75% Water/25% Methanol. You can see the at 100% water injection, only 3% of w/f fuel ratio is enough to replace 2.5 point of a/f ratio (dotted line). As soon as 25% of Methanol is added, the a/f ratio is dropprd to 12.0 - loosing some cooling capacity


The two charts show (first and last) that you will require to inject twice the amount of methanol to equal the latent heat of water alone. Methanol is relatively low cost and very effective as a coolant so what is the problem?

When higher concentration of methanol is injected, you need to lean your engines a/f ratio to accommodate the extra fuel or your engine will bog down and loose power. Consequentially - one runs the risk of putting the engine into heat stress if the supply of methanol is suddenly interrupted. Injecting water does not affect the a/f ratio. It appears that 50/50 mix has the best of both worlds.

In either cases, having a good w/a injection system with reliable "system fault" diagnostic capability is essential especially if you are running a high concentration of Methanol.

The Alchemist 22-04-2012 01:41 PM

Re: Looking for a Water:Meth ratio vs cooling chart
 
I'm the friend the OP was talking to. I'm looking to add water/meoh in order to keep my chamber temps under control while making upwards of 700+ rwhp. I have an LS1 motor, and #7 cylinder has a notorious issue with being hotter than the other cylinders due to logistical issues with the cylinder head and how the coolant flows through the block and into the heads. I was having a technical discussion with someone who kept saying to run 100% meoh as it cools better than water, but I disagreed with him stating that meoh cools 'quicker' since it has a lower evaporation temperature, but once the chamber mixture is ignited, the meoh only serves to add to the latent heat in the chamber, where the water will help to control the chamber temperature through the combustion cycle far better than running 100% meoh.

I was a formulation/qc chemist at Sunoco early in my career as a chemist, and I remember experiments testing the combustion chamber temps with regards to different air/fuel ratios as well as different octane levels in the gasoline. Unfortunately, that data is still at sunoco. So I was looking to see how the different ratios of meoh/water impacted combustion chamber temperatures. If you can keep the combustion chamber temps under control, the need for elevated octane levels decreases. Knock/pre-ignition is impacted far greater from chamber temperature than cylinder pressure, ie compression ratio or boost pressure. So keep the temperature in check and you can run more compression, more boost, more timimng and less octane.

Howerton Engineering 24-04-2012 06:10 AM

Re: Looking for a Water:Meth ratio vs cooling chart
 
A few observations from the data logging I have done in the past.

Due to physical properties noted above, water does cool the intake charge some, but not near as well as methanol due to the boiling point, etc. Water seems to do much of it's cooling in the combustion chamber by absorbing some of the heat of the combustion process, and slowing the burn retarding it over a greater number of crank degrees.

One item that should be noted is methanol combustion actually cools the combustion process as well due to cooler burns characteristics vs gasoline.

What usually drives the direction I see tuners going with either water and methanol concentrations is the limitations of the application. Water likes dynamic compression, either high static compression or lots of boost. You also need a strong ignition to light the flame front when water to fuel ratios start to rise other wise power will be lost and misfires will occur. Larger amounts of methanol are much more forgiving because it burns.

The main reason, in my opinion, methanol is more popular than water is in the way the modern ECU works(and weak factory ignitions). The driving force in timing tables and fuel dumping to cool the chamber, is knock and IAT. With a higher octane vs pump gas and cooler burning temps methanol helps the knock issue. The biggest benefit seems to come from cooling the inlet charge, enabling the ECU to give maximum timing. This is assuming you can blow it past the IAT sensor. The IAT timing compensation can be a very strong and evil thing, and water doesn't affect it as much as methanol.

Now, if running a stand alone you can throw out the ECU issues, and with a strong ignition run straight water and do miraculous things. But, with stock ECU's and crap gas, it's much easier, and sometimes more productive, to run high concentrations of methanol for maximum performance.

PobodY 24-04-2012 07:51 AM

Re: Looking for a Water:Meth ratio vs cooling chart
 
On a purely thermodynamic basis, doesn't water have a higher latent heat of vaporisation than methanol? On that basis it should absorb more heat from the system; MeOH should cool sooner and faster, but ultimately take less heat to do it?

I'm not arguing with the empirical evidence, but I'm also a chemist (albeit inorganic, so this isn't my area) and what The Alchemist is saying makes sense to me from.

Richard L 24-04-2012 08:37 AM

Re: Looking for a Water:Meth ratio vs cooling chart
 
The rate of evaporation, thus cooling is governed by the saturated vapour pressure value. It is a thermal dynamic topic, no chemical change has taken place.

Once the equilibrium is reached, no more cooling will take place untill temperature is increased or pressure reduced.


http://www.aquamist.co.uk/forum/methanol.gif http://www.aquamist.co.uk/forum/water.gif



The following chart represents the total internal energy of water. At 370 C, water comes a gas (single molecule).
You can look this up on the steam table or enthalpy/entrogy property of water in any reference book.
http://www.aquamist.co.uk/forum/WPT.gif

Link to a simple calculation (cooling by water).
Substitude in the methanol properties to made a comparison.
http://www.aquamist.co.uk/rescr/faq/...rmass.html#cal


The Alchemist 01-07-2012 11:46 AM

Re: Looking for a Water:Meth ratio vs cooling chart
 
Thanks for the replies guys. I still have people screaming that 100% methanol cools better, and I laugh to myself. The only way it will cool the chamber is if you are removing gas from the mixture with the added methanol you dump in, but most people don't. They tune their motor to run at 11.0-11.5 afr in boost, then add methanol injection and use it to crank up their timing 4-5 degrees. Now you've used the methanol as an additional fuel source, not a replacement. Horsepower is heat. On a given setup, the more power you make, the more heat you generate. So by adding methanol to the combustion process instead of water, it is adding to the heat equation, at least that's how I view it. Maybe I'm wrong, who knows. I plan to run 50/50 water/meoh as I feel it gives the best results between cooling, added octane, and the ability to tune for more power. I'm no longer on a stock shortblock, and built my motor to handle the boost in terms of ring and bearing tolerances. Of course I'll be running an HFS-3 kit ;).

Howerton Engineering 01-07-2012 04:53 PM

Re: Looking for a Water:Meth ratio vs cooling chart
 
In the scenario you have described, looking at the process from one angle one would come to the conclusion that adding methanol on top of gas without altering the tune would add heat. I can offer a data example to show what we have measured. You maybe correct, but it would be difficult to confirm.

The test was on a SC car that was not tuned for methanol, so we could turn the kit ON and OFF without damage. When injecting 100% methanol, at 25% to fuel by volume, the net effect was higher power and 150F lower EGT's.

The methanol cooling the IAT's ( a 120F net drop to 40F sub-ambiet) and cooler burn characteristics in the chamber could be attributed to the cooler EGT's. But, one also has to notice that the timing can be advanced due to the increase in octane( and knock sensor activity on this vehicle). On this vehicle, the timing would be advanced as much as 10 degrees by the ECU based on IAT and knock measurements.

So cooler EGT's could also be attributed to the advanced timing, but without measuring the CHT and water temp changes it would be difficult to test. Also, fixing the timing between tests would also help. We did not see any appreciable water temp changes in the tests, and were not measuring CHT.

The stoichiometric ideal of methanol works in favor of us in this scenario. While injecting 25% to fuel, it is the equivalent of 10% of gasoline. So while it affected the AFR about 1 full point, the volume used greatly helped the IAT cooling requirements of the motor.

Sometimes looking at one aspect of the process can be beneficial but can also be deceiving without seeing how all the processes interact. I am certainly not saying 100% methanol is better or worse than water, a blanket statement like that is foolish.

I have to stress, what fluid works best is extremely dependent on the application.

The Alchemist 02-07-2012 01:28 AM

Re: Looking for a Water:Meth ratio vs cooling chart
 
Thanks for posting your experiences Howerton. I'm running an LS1 in a 4-gen F-body (camaro/firebird) which was never intended to be run FI from the factory. The top rings are spec'd at 0.009" - 0.015" ring gap, and with hypereutectic pistons, it doesn't take much to get those rings to butt together and take out ring lands. Typically this occurs somewhere north of 550-600 rwhp. What does it? Heat. SO the question then comes to how do you keep the pistons cool the best. Sure the methanol helps, but I still feel that the water element is benneficial in keeping temps under control.

Is the HFS-3 kit even able to run 100% methanol?

Howerton Engineering 02-07-2012 02:36 AM

Re: Looking for a Water:Meth ratio vs cooling chart
 
I agree that water is very beneficial in your case. As I said before, it is very dependent on the application. If you are only looking for cooling, then water will work. You will hit a point where water will begin to retard the burn, and without timing advances, you could loose power, but that will depend on how you inject it and how much you ultimately use. You may know much of this already, it's just there is never really a universal answer to what fluid is best, which most folks are looking for. In your case, large displacement, no power addition wanted, no tuning changes, etc, a 50/50 mix will probably work great.

All of the parts in the 3 are perfectly fine with 100% meth, the pumps are what may be affected in the long term.


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