Water/Methanol Injection

AEM's Water Meth Injection Controller

When it comes to looking for more power in a forced induction set up, alternative fuels are a very viable option. This article is specifically about water methanol injection, although we have another one written about ethanol (E85) as well. Often times, when people first hear about water methanol injection, they become skeptical due to the “water” part.

We need to talk about what it is so we can give you peace of mind. Water methanol injection is exactly what it sounds like: a mixture of methanol and water that is injected into an intake set up or intake manifold. As it is sprayed, the water turns to a vapor; when it turns to vapor, it absorbs heat. It absorbs A LOT of heat, actually. I’ll show a video of intake temps and boost temps after the injection. The methanol burns slower and a little different from gasoline which provides a high octane rating (or just a knock threshold rating).

So we know that water methanol injection both lowers intake temperatures and also increases octane ratings. AEM and Snow performance say that it will increase to 116 octane, but it would depend on what your mix is. You have three different options: boost juice (or some kind of pre-mixture specifically for an injection set up), a 5 gallon tank of methanol you mix yourself, or windshield wiper fluid. Yes, I said windshield wiper fluid, but I mean a very specific kind. The fluid can’t contain glycol. You’re looking for the winter blue stuff (-20 and -30). Depending on the brand, the wiper fluid will contain anywhere from 27%- 36% methanol.


Let’s talk about what methanol is. Methanol is an alcohol compound with one carbon atom, one oxygen atom, and four hydrogen atoms (CH3OH). Methanol is also known as wood alcohol, carbinol, and methyl alcohol, which is very poisonous and very flammable. It has no taste or color, and pure methanol flames are colorless. Antifreeze, Formaldehyde, and fuel all have methanol as a common ingredient, and methanol is added to ethanol to prevent others from trying to drink it.

Now if you watch this video of a Mini, you can see the crazy cooling effects that this injection system has. This video blows my mind at the end, when there is almost a 200 degree difference between intake temperatures and boost air temperatures.

So this cooling effect, combined with the high octane and slow burn that methanol offers, creates amazing performance capabilities. Since there is a higher octane level, you can further advance your timing.

For those of you that are into chemistry like me, here are some equations to let you compare methanol to gasoline. It also explains how much higher cylinder pressures get with methanol. This correlates to horse power and turbo spool.

Methanol vs Gasoline

Gasoline –  C8H18 + 12.5 O2 → 8 CO2 + 9 H2O  DH (heat released) = -5460 kJ/mol

Methanol – CH3OH + 1.5 O2 → CO2 + 2 H2O DH = -726 kJ/mol

This demonstrates when one mole of methanol is burned in comparison to one mole of gasoline. The equations show that methanol produces a lot less energy per mole then gasoline, about 47%.

The energy being let off is heat energy, so you can see that it is significantly “colder”.

Now if we change up the equation so that the amount of oxygen in the atmosphere is the limiting factor, the equations look like this (below)

Gasoline – C8H18 + 12.5 O2 → 8 CO2 + 9 H2O  DH (heat released) = -5460 kJ/mol

Methanol – 8.33 CH3OH + 12.5 O2 → 8.33 CO2 + 16.67 H2O DH = -6047 kJ/mol

So before we had 47% less thermal energy with only 1.5 O2 molecules. When we bump up to 12.5 O2, our thermal energy increases to 11% more than gasoline. On top of that thermal increase, there are also more combustion products to be found. And for those of you running water meth in a turbo application, that means there is potential for faster spool rates. Now having 25 products as opposed to 17 means higher cylinder pressures which means more power!

So by lowering the amount of methanol and oxygen used to 90.7% we can find the same thermal energy found when one mole of gasoline is used!

Methanol 7.53 CH3OH + 11.3 O2 → 7.53 CO2 + 15.1 H2O DH = -5460 kJ/mol

So for methanol, you get 22.6 (=7.5+15.1) moles of combustion products compared to 17 from combusting gasoline. This corresponds to a 22.6/17 = 32.9% increase in cylinder pressure at the same thermal energy. If you max it out and use up all the 12.5O2, you would get a 10.7% (=6047/5460) increase thermal energy plus 47% (=25/17) more of combustion products. So we are looking at 11% more heat and 47% more exhaust products. Turbos spool off heat and exhaust products, so there is some crazy potential for spool rate changes and all around efficiency.

Those numbers are insane! Reread that a couple times if it didn’t make sense and try and see it. Those equations are truly the best way to see methanol’s full potential as an alternative fuel. Understanding those equations and then seeing an injection system like this put into place will amaze you with the possibilities.

We plan to install and run a water methanol kit on my Subaru. I’m still trying to decide on which kit to run, as there are several options. Keep an eye out for a how-to-install post and review on the kit we choose.





5 thoughts on “Water/Methanol Injection

  1. Good info…I’m thinking this may be a good ‘safety-feature’ w/ summer’s heat.

    I hate wiring, but if it’s a boost-triggered shot of meth-juice then I can probably figure that much out.

    I’ve used a something kinda/sorta/maybe not so much w/non-glycol washer fluid as a TMIC sprayer on a previous project.

    For a Sedan, get the ’95-’99 Legacy wagon’s washer fluid tank as it has 2 pumps (front and rear windows) – and use one for the cooling shot and one for the windshield. It bolts right up – should fit the Impreza too.

    I really don’t trust my 4EAT to stand much more HP/ft-lbs, so I’m not looking more more power, just safe(r) power.

    Chem = FTW! 🙂


    1. I have a friend that ran a Meth injection set up on his naturally aspirated EJ22E that he turbo’d and running stock ignition pushed 16 PSI of boost with no knock. These kits are safe an allow you to push for a little more power.
      For sure a great thing to run for summer heat.

  2. AEM’s low profile 1-gallon tank includes a more accurate conductive low fluid level sensor by eliminating any chance of interference. The connector for the sensor is a positive lock design and the wires are color matched to the harness.

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