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Meth/water injection explained

13 December 2010 3 Comments

I was at Street 2 Strip on Friday evening and while walking around the pit area I noticed a 200sx with a fat set of D2 brakes resting nicely under the arches, while inspection the Nissan a little bit closer I noticed a Methanol/Water injection system in the boot. So I decided to do an introduction blog on Meth/Water injection.
Methanol/Water Injection remains a popular upgrade within the high performance cars these days. It’s rather hard these days to believe that injecting water into an engine in can increase power figures, but the truth is that water/methanol injection is beneficial to all forced air engines these days. The main function of water/methanol injection is to prevent detonation, but that’s not to say it can’t also increase horsepower/torque output by 7 to 15 percent with proper tuning.

What is Methanol really?
Methanol is an alcohol compound comprised of one carbon atom, one oxygen atom, and four hydrogen atoms (CH3OH) and is also referred to as wood alcohol, carbonic acid, and methyl alcohol. This poisonous, flammable, and relatively volatile liquid is naturally occurring, and domestic uses date as far back as the third millennia B.C. Back in the day Methanol was combined with water and used during WWII in supercharged fighter planes and bomber engines. After a few fast years, it was banned in both F1 and NASCAR in the ’60s for adding too much power to competition engines.

How does the Methanol/Water injection work?
Basically Methanol/Water injection helps prevent detonation. Substances heat up when they’re compressed, and in traditional petrol engines, detonation occurs when a cylinder’s air/fuel charge compresses and heats to the point of auto ignition during the compression phase, before it can be lit at the proper time by a spark plug. If this occurs a few degrees of crank rotation in advance, the consequences may not be bad. But if it occurs further back in the compression stroke, in high-power instances, it can easily destroy an engine’s internal components. Meth/water injection systems deliver a finely atomized mist of a methanol/water mixture to an engine’s cylinder charge, and as the mixture absorbs heat and vaporizes, temperatures inside the cylinder are reduced and the propensity for detonation is decreased.
While water is not flammable, it has a greater capacity to cool intake charges than methanol alone. This is why most manufactures recommend that a 1:1 mixture of Meth and water be injected into your engine. Methanol also effectively increases the octane rating of your fuel, giving the benefits of running higher octane levels than your normal 95 pump fuel. The evaporation effects of the water, plus the octane boost of methanol, allows your motor to run more advanced ignition timing and/or boost to create additional kilowatt with proper tuning. A general rule of thumb is that an engine will output one percent more power for every 10 degrees intake temperature is decreased.

Here is a diagram that illustrates the cooling process.


  • "yours truly" said:

    Love it, easy read and communicates the concept perfectly!


  • roeshdean said:

    i found article very interesting how do i apply it in my car


    Blair Reply:

    @Roeshdean you will need to buy a Methonal/Water injection system. We will be stocking the AEM one from about Feb of next year.

    @Barend thanks man, after seein the setup in the 200SX i realised the Meth/Water injection is still very new to the South African tuner.. so im glad my explanation was atleast understandable :D


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