All about MINI An Introduction to Water/Alcohol Injection Systems

Meth kit.jpg
There is no question that Water/Alcohol Injection (WAI) is a valuable tool in the tuner’s arsenal for obtaining more power from an engine. The...
By Steve · Feb 8, 2018 ·
  1. Nathan

    Nathan Founder

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  2. BlimeyCabrio

    BlimeyCabrio Oscar Goldman of MINIs
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    Very good write-up. I believe it's strong on the facts and constraints of various systems. Only critique would be that it could perhaps add some additional conclusions specifically around the realistic value of different types of systems for MINI owners with different setups and objectives. While I think it's very fair with assessments such as "some is better than none" and "progressive can provide some benefit if you know its limitations", I would suggest some more specific recommendations, such as "PWM with adequate failsafes is the only practical solution for highly tuned track cars where the intent is to maximize performance by tuning for the presence of water/meth" and "progressive systems can provide some cooling benefit across the boost range as well as high-torque knock suppression in street cars where tuning for meth-dependent maximum performance is not the objective" or something like that... because I believe pretty strongly that MANY folks can be well served by relatively inexpensive systems.... but the guys making big HP can certainly justify the more expensive PWM rigs...
     
  3. CarlB

    CarlB Active Member

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    Great article! There was a rant on my club web page about Motoring Alliance being a social networking site, and they were looking for hard core technical information. I have been a racer all my life and read a lot of technical literature. Your article was as good an explanation of the mechanics of the different systems as I have seen anywhere. Especially sense it was on a free social networking site. Not only that but it was well written.
    I have played with water injection ever sense I read Ricardo’s first printing of the “Internal Combustion Engine†Henry Ricardo discovered the difference between detonation and pre-ignition. All his early work was involved improving engine efficiency by raising the compression ratio. To this day every refinery in the world establishes octane value on an engine designed for that purpose by Ricardo. In the early part of the last century he built a two barrel carburetor that had water on one side and gas on the other. The water injected engines were used in London busses, and proved affective.
    My own experience with water injection is that engines are tolerant of too much water, but if the engine is tuned to need water be very careful of leaning the amount of water. Single stage systems that add more water than is required at low speeds do not harm power, and have adequate water for cooling at higher speeds.
     
  4. CarlB

    CarlB Active Member

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    Paul you would like to have clear conclusions to the article, but I am not sure it is that easy to define. It’s all in the tuning, and there are too many variables. Water injection was extensively studied for aircraft engines. The optimum level of performance was obtained with a ratio of half the amount of water to fuel. Here are some but probably not all the variables. The biggest single thing is engines will not loose power over a very wide range of water to fuel injection. This makes the simple systems very attractive. One issue the article did not address was the amount of atomization of the water. Water works as a knock suppressant because the latent heat of vaporization for water is extremely high. That is why it cools the intake tract and cools the combustion chamber preventing the fuel from burning early. The disadvantage is the size of the atomized droplets is very important. If the droplets are too big they will pass through the system with no affect. If they are too small they vaporize in the intake and displace fuel air mixture and the engine looses power. All the car manufacturers I know about including Mini on the R 53 (I do not know about the R 56) cool the combustion chamber to prevent detonation by running very rich fuel mixtures under boost. You can make more power if you lean it out. Water injection holds the promise of allowing that. The PWM systems are technically more sophisticated and offer the potential to of better control. They might even work slightly better, but the other systems are out there working, and it will take a very sophisticated well tuned PWM to outperform a well developed two stage system. I am not aware of anything working better than the simple two stage systems. There is a popular form of oval track racing called sprint cars. They use alcohol for fuel, and a fuel injection system that is not a lot more sophisticated than the two stage system of water injection. They generally have three stages. It works very well because engines can tolerate a wide air fuel ratio when they burn alcohol. Well financed knowledgeable people have tried different more technically sophisticated system and have not realized an advantage. One other experience I had was with a Ford Fiesta. We took a totally stock car and changed the pistons to raise the compression to 13 to 1. We used water to suppress the knock and had a very unique proportional signal that worked. (It would only work in a naturally aspirated engine.) In a full emissions lab dyno cell we could advance the timing 20 degrees at full load and nothing changed. Water controls the burn rate and prevents detonation. Get it to vaporize in the chamber and it will work.
     
  5. Jeff H

    Jeff H New Member

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    Blimey and Carl,

    You both have good points and observations. When I was asked to write this article it was a simple introduction to water/alcohol systems. My intent was to lay the foundation for the majority of readers to become educated and let them pursue more information on their own, and let them formulate their own conclusions. I tried to present as un-biased an article as I could so as to leave each vendor as happy as possible since this was written for a neutral medium.

    Hopefully others will contribute to this thread expanding the readers knowledge on this subject.
     
  6. BlimeyCabrio

    BlimeyCabrio Oscar Goldman of MINIs
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    Jeff - THANK YOU for the effort that went in to this - really is well done - and thanks for all you've taught me about this subject over the past several months!

    Glad to have you here.
     
  7. Nitrominis

    Nitrominis Banned

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    Nice write up.
     
  8. imspencerwithanr53

    imspencerwithanr53 New Member

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    Very nice write up. I learned a lot about WAI systems. Thank you. :)
     
  9. rum4

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    I know this is old but I just learned a lot on the water/alcohol injection system, thanks Jeff
     
  10. CarlB

    CarlB Active Member

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    This is a subject I have a lot of interest in, as evidenced by my previous post. I thought I would add something to stir up the pot. Methanol is a high octane fuel and has a higher heat of vaporization than gasoline, but water is the more cost effective and perhaps as effective an additive to prevent pre-ignition and detonation. First let me state that the assumptions are that you are comparing the same engine that needs more octane or is being run rich to control pre-ignition (if the chamber gets too hot during the compression stroke the fuel will ignite). The R-53 is tuned rich under boost to control pre-ignition. Plain old water is very unique. It has the highest latent heat of anything I know about (970 BTUs per pound) and expands 1600 times from a liquid to a gas. Methanol has a latent heat of 473 BTUs per pound. Methanol burns and increases the octane rating of the fuel; it also lowers the temperature of the intake charge. Lowering the intake charge temperature has the same effect of preventing pre-ignition as higher octane. Pre-ignition is the spontaneous ignition of the fuel because it got too hot. Octane is a resistance to ignite as the temperature goes up. All the experimental work on water injection was started with just water. Alcohol was added to prevent freezing. During the Second World War a lot of experimentation with water injection was done. Pratt and Whitney almost tripled the power of the engine in the P-47 and water injection was a big part of that. Water or water methanol were not the reasons the engine made more power. The reason was that the addition of water or water methanol lowered the temperature enough to add more boost. The work done during the war also showed that a 50-50 mix of water to methanol had the best results for increasing power. The problem with water is it is very difficult to vaporize. The whole combustion process from air entering the supercharger to exiting the combustion chamber is obviously very fast in an engine spinning at high RPM. To expose the water to the enough heat for a meaningful amount of vaporization, the water must be atomized into very fine droplets. In my opinion adding methanol lowers the surface tension and has the same effect as smaller droplets. I can’t prove it. I do not have any hard data, but I believe it is logical. Our community seems to believe the active ingredient in all of this is the methanol. I would be glade to discuss why I think water is really the main player.
     

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