Water, Methanol, and You

Spraying water into your engine may seem a bit counterintuitive, but there’s actually a good rationale for doing it and you can benefit from it in certain circumstances.

We all know that any car can benefit from cooling the intake air. Cooler air compresses better and provides more oxygen for a bigger bang. While it’s probably not practical to refrigerate the incoming intake air in quantities that your engine needs in order to operate efficiently, there may be another way of cooling the air down on its way to your cylinder.

For normally aspirated cars (NA), residual heat is soaked up by your intake parts and a bit of that heat is then transmitted to and heats up the air passing through the intake system. The difference of air temperature from ambient air temps to intake air temps is this heat. A turbo in a car can heat up by as much as 1025°C (1875°F) on the hot (exhaust) side and average about 950°C (1750°F) if producing boost continuously. In addition to the heat transference from the hot side, as the air is being compressed, additional heat is being created on the compression side. In other words, in addition to scavenging heat off the turbo housing itself, the air is being heated directly through compression. What all this means is that the air passing from the outside through the turbo on its way to the intake is very hot, and this is where you can gain the most benefit from a water/methanol injection system. The higher the compression (as measured in PSI), the hotter the air will get and the more you will benefit from the cooling effect of the water/methanol injection. This is not to say that non-boosted systems cannot benefit from water/methanol injection, it just means that boosted systems benefit more.

Do I need water/methanol injection?

Contrary to what the masses might have you believe, water/methanol injection isn’t the silver bullet to help you gain massive amounts of power simply by installing a kit. The fact is that water does not burn and methanol burns about 60% slower than gasoline and has about 43% of the energy of the same volume of gasoline. What this means is that the water being injected contributes nothing to the combustion process and the methanol contributes very little. If this is the case, one would wonder what the advantage of injecting the two liquids into your engine has. The answer to that question is two-fold… one is that when water and methanol evaporate, it absorbs heat and dissipates it. Additionally, due to the fact that methanol has an effective octane rating of 110, it can increase the octane of the air/fuel mixture making it less likely to pre-ignite in your cylinder.

First, before you spend money on that cool water/methanol injection kit, you need to know a few things. The first thing you should be paying attention to is the difference between the outside air temperature and your intake air temperaturewhen the car is moving and the gas pedal is applied to see how much of a difference there is. Don’t bother looking at the difference when your car is sitting at an idle in traffic. While there is power loss associated with hot air going into your intake, it doesn’t matter since you aren’t using any significant amount of power in bumper to bumper traffic or at a stoplight. Where it does matter is when the air is being sucked into your engine when you are trying to accelerate or when you are maintaining speeds close to your top speed.

If you have an intake air temperature (IAT) of 10°F higher than the outside air temperature (OAT), your intercooler is doing its job (or your intake isn’t absorbing that much heat)… there’s not going to be much benefit to spraying water/meth and it could actually hurt your power output (water doesn’t burn). If your IAT is between 10°F and 30°F above the OAT, the benefit of water/methanol injection is borderline… in other words, although you will benefit from the cooling effect of injection mix and the higher octane, but you will lose approximately the same amount of power due to the fact that water does not burn. The net effect is essentially null. If you are experiencing IATs greater than 30°F as compared to OAT, first evaluate whether or not you have an adequately sized intercooler and determine if a more efficient intercooler will do the job. If that is not an option for you, then water/methanol injection may be what you need to cool that intake air temperature down.

Will water/methanol injection add power?

Water/methanol injection in of itself may add a few HP in hot weather; however, in cooler temperatures water/methanol injection can actually cost you a few HP. So, in the long run, no… the power gains that you might experience with water/methanol injection alone are not going to be significant. What water/methanol injection will do, in most circumstances, is preserve what power you have in hot temperatures.

Now with all the above said, you can have your car tuned to specifically take advantage of the increased anti-knock properties of your air/fuel mixture, which in turn will result in measurable gains. For all cars, timing can be increased allowing for more compression before the air/fuel mixture is ignited due to the higher octane level of the fuel that enters the cylinder. More compression = more bang = more fun.

In addition to advancing timing, for forced induction engines (turbo or supercharger), running water/methanol injection means being able to increase the charge air pressure even further. More air = more bang = more fun.


If you tune to take advantage of the water/meth injection, you cannot safely run your engine without it! This is a really important decision. Yes, your best gains happen when you tune your car to take advantage of the water/meth; however, because your car now depends on a regular supply of water/meth, depriving your car of this now vital elixir will result in engine damage! If you do not tune for water/meth and you run out, oh well… your car will adapt. If you are tuned for water/meth, you should have some failsafe or warning system to let you know if you run out, if you bust a line, or if your pump decides to quit pumping. All of these things will result in bad outcomes.

Since water doesn’t burn why use it and not 100% methanol?

First off, the primary benefit of water/methanol injection is heat absorption. Water has about two and a half times more cooling potential than methanol. What this means is that you have to inject two and a half times more methanol to get the same amount of cooling for the same volume of water.

The effect on pre-ignition is totally different. Water suppresses knock by quenching peak flame front temperatures (too fast burn promotes pre-ignition). A perfect charge distribution produces lean and rich pockets. Lean pockets burn at a higher temperature (oxygen-rich = faster) compared to fuel-rich pockets (excess CO slows down burn speed). Methanol suppresses detonation by increasing the octane value of a given fuel grade. Since a large amount of methanol is required to control in-cylinder temperatures, air/fuel ratio will be affected significantly. Some fuel has to be removed to avoid over-rich mixture.

Methanol is a flammable liquid. If you develop a high-pressure leak that results in blowing the methanol into a fine mist, it will ignite and an awesome fireworks show will ensue. Keep in mind that many water/methanol kit pumps will pressurize the mixture to 300 to 500 PSI. The high pressure is needed to properly atomize the mixture with the air. If the mixture is atomized and then sprayed on a hot component (like your exhaust), the resulting explosion would be fun to watch but provide zero entertainment value for the driver and passengers of the car that is exploding. Additionally, the boiling point of methanol is 149°F. Do the math and ask yourself, do you think that the inside of the engine bay on a hot summer day can reach 149°F? I can answer that one for you… according to popular lore, the temperature inside the passenger compartment of a car sitting in direct sunlight can climb to temps as high as 172°F. Now, ask yourself again, is it okay if the methanol inside the lines in my engine bay start to boil?

Lastly, methanol levels above a 50/50 mixture of water/meth make the fuel mixture MORE prone to pre-ignition. Although methanol increases the octane level of the fuel, it is all but vaporized when it enters the cylinder due to evaporation… and we all know that flammable substances do tend to be more flammable when vaporized. You can put matches out all day long in a bucket of gasoline without fear of igniting it… as long as the match passes through the vapor barrier between the outside air and the liquid gasoline without igniting it. It’s the gas fumes that you need to worry about. Just like gasoline, methanol fumes are more flammable.

So why use methanol at all?

Although methanol is not as efficient at absorbing heat, it will absorb what it can very quickly when compared to water. Considering the velocity of the air that is being sucked into your intake, speed is important. You want to cool as much of the air charge going into the intake as possible in order to put more air in. Water, by itself, does not work quickly enough to absorb enough heat to be as effective. Additionally, methanol does have an octane boosting property that your engine can take advantage of (to a point). As discussed above, water is a detonation inhibitor… meaning that has a tendency to put the fire out by itself.

How much methanol should I inject?

The answer to that question is simple and not simple all at the same time. What you want to be able to do is inject 12-15% water/meth as compared to your fuel flow for most applications.  Okay, simple enough… but… uh… whut? Fortunately, most water/meth injection kits will also tell you which injector you need to run for your HP level. This is an approximate guess since motors are all different, but it will get you in the ballpark and you can tweak it from there.

Okay… I’m going to pull the trigger… what kit is the best?

I love these questions… and the answer to that question is: “The one that works best for you“. Now, I know that’s not the answer you want to hear, but the fact of the matter is that any kit that is made by a competent manufacturer is going to do the job for you.  The question you have to ask yourself is, “what features are most important to me in my application?”  You see what I did there?  The best kit is based on how you are using the kit.  If you are simply using the kit to enhance cooling and you are not tuning for it, there’s no reason to spend a $1000 on a kit with an advanced failsafe built in and tons of gauges and other miscellaneous crap that you don’t need.  On the other hand, if you are tuning to squeeze ever ounce of power that the water/meth injection kit is going to get you… you may want to consider spending more to prevent your car from blowing up if all of a sudden your water/meth kit ain’t water/mething like it should.

I’ve got my kit, where do I buy the juice?

Well… as they say in the streets… we can do this the easy way or the hard way.  Wait… okay, maybe they don’t say that in the streets.  In any case, there is an easy way (typically more expensive) and a hard way (less expensive, more Dexter mad scientisty) to get your meth.  Don’t like to do math?  You just want to buy the stuff in a bottle and pour it in?  Snow Performance’s Boost Juice is for you!  51% distilled water, 49% pure methanol goodness.  The stuff is all red so as to signify that you will go all red alert when you pour it in.

Want to mix your own but have limited resources?  Go out and buy yourself some -20°F  BLUE <~~~ emphasis on BLUE… windshield wiper fluid which contains approximately 32% methanol and 68% distilled water… then mix it with three bottles of HEET in the YELLOW <~~~ emphasis on YELLOW… bottle.  HEET is a fuel additive that is used as a line defroster and is 99% pure methanol.  The other stuff in the red bottle has crap in it that you can run in your engine, but it does nothing to help with your injection and it has less methanol in it.  This will give you a 51% distilled water and 49% methanol mix.

Or…. you can go all mad scientist and mix your own stuff from scratch!  You want to get some VP M1 methanol (99.9% pure methanol) from your local speed shop, some distilled water from Walmart, and a scale.  Yes…. a scale.  The mixture is by weight an not by volume!  Water weighs approximately 8.35 lbs/gal.  Methanol weighs approximately 6.63 lbs/gal… so by volume, you’ll be mixing more methanol to get to 49% than water.  Use a scale, it’ll be much easier… but just remember… if you are pouring the methanol into the water and the water already fills 1/2 of the jug, you won’t be able to get enough methanol into the jug to reach a 49% concentration by weight.

Be careful when storing your methanol.  Make sure it’s sealed tight (it will want to evaporate) and is away from any heat sources.  And most importantly, don’t drink it. It’s poisonous.

Steam clean your engine!

Okay, some of you may have heard that water/meth injection is a great way to clean your engine due to the fact that the water will turn into steam and steam clean the inside of your engine.  Yes, this is true. Steam will break down oil deposits and loose material inside of the cylinders and the valves as well as break up carbon buildup. For you GDI (Gasoline Direct Injection) types who worry that their valves are getting all gunked up with carbon, water/meth injection can help reduce the carbon buildup.

The final word

Water/methanol injection has become the latest unicorn paradigm.  It replaces the CAI as the silver bullet for instant power.  Word on the street is that simply by spraying water/meth you can increase your horsepower by cooling the intake temperature.  While water/meth injection can cool your intake temps, the question you have to ask yourself is, do you really need to cool your intake temperatures? The answer to that question lies within the answer to another question, how much hotter is your intake temperature as compared to the ambient outside air temperature? Water/meth injection will not lower your temperature below the ambient air temperature no matter how much you spray.  Additionally, because water doesn’t burn and methanol has a much lower power potential, you can actually lose power as a result of spraying.  The benefit of water/meth injection is far less with normally aspirated motors as compared to forced induction.  Weigh the benefits carefully to determine whether the expense of having and maintaining a water/meth injection system is for you.

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About the author: Bob

I am a 21 year retired Army veteran with a background as a CH-47 helicopter Flight Engineer. For the past 5 years I have been a Genesis Coupe enthusiast and am currently a Moderator and Contributor for GenCoupe.com Forums, author of the "The Ultimate Genesis Coupe Newbie Guide to Modding", and the "Ask a Geek" sub-forum. Additionally, I am an administrator and event organizer for GenSport United as well as several other groups on Facebook. While I do not pretend to know all things with regard to the Genesis Coupe, I have dedicated a substantial effort to learn as much as I can and share it with whoever will listen.

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