Understanding Diesel Water-Methanol Injection

June 9th, 2011

By Diesel World Staff

Photography: Joe Daniels

How does diesel water-methanol injection work, and what are the benefits? We bring you the complete story.

Debunking the Myths With Facts

As fuel costs go up, along with horsepower and torque levels from aftermarket mods, many diesel enthusiasts are turning to water-methanol injection for increased mileage and cooler EGTs.

So what’s the science behind it, and how actually does it work? We turned to Matt Snow, of Snow Performance, who has been a pioneer in the development and application of water-methanol injection on both gasoline and diesel vehicles. He gave us detailed answers to common questions about water-methanol injection to help debunk any myths and present the science behind the story.

What Happens When You Inject Water Into a Diesel?

While water is a bad thing when found in the fuel source (fuel line freezing, effect on fuel injectors, etc.), when water is injected into the intake manifold of a diesel, increases in power, fuel economy and lower EGTs are the main benefits. The key to making the system work is fine atomization and injection at the correct time.

Many run 100% water to cool EGTs for a degree of safety while towing, racing or pulling. It’s cheap insurance. Over-the-road class 7&8 trucks are also using 100% water to primarily increase fuel economy, as well as to allow faster speeds on the mountain grades––where high EGTs would normally require the driver to back off the throttle. The drawbacks to 100% water are: (1.) increased propensity to quench combustion––less can be injected before eliciting combustion quench, so less total EGT cooling can be attained with straight water than with a methanol-water mix; (2.) Freezing in cold climates; (3.) less overall power increases, roughly 8% on water alone, as compared to a 20% increase with 50% methanol.

What is Methanol, and What Does it Do When Injected Into a Diesel?

Methanol also goes by the names “wood alcohol,” “methyl alcohol” and “methyl hydrate.” It is the same common alcohol used in “alcohol-burning” race cars. It is commonly used as antifreeze in -20° F blue winterblend windshield washer fluid, as well as a gasoline dryer in “Heet.” It is also used for keeping air lines dry in trucks that have airbrakes. If used as the sole fuel in a diesel, it requires an ignition source, because it won’t auto-ignite––its auto-ignition temperature is 470º C. Please note that this compares to diesel fuel’s ignition point of 210º C. This is important when discussing water-methanol and methanol injection and its effect on peak cylinder pressure.

When injected before the intake manifold of a diesel, the fact that it has a cetane of (4) means that it slows combustion and increases ignition delay (the time from start of diesel injection to start of auto-ignition). After ignition, cylinder pressure rises at a faster rate. As a result, “diesel noise” is slightly increased but peak cylinder pressure is only slightly higher, due to ignition delay and the combustion conditioning effect (the available diesel is more-efficiently burned in the later diffusion-controlled stage of combustion).

More power is attained, due to the fact that the diesel is more-efficiently and -completely burned, and the added methanol is a fuel source. Also, due to the fact that more power is generated on the power stroke (as the piston is going down after TDC), resulting in more net-positive torque means that more power is generated with a given amount of fuel. There is potentially more power, since more diesel fuel can be injected safely because of the reduced combustion temps.

What Is the Best Ratio of Water-methanol for Different Applications Such as Towing, Street Driving and Competition?

For towing, the most cost-effective fluid is blue winterblend windshield washer fluid (approx 30% methanol), because it is only $1.50 per gallon and is readily available. For all other applications, 50% methanol is the best mix of power, cost and safety (50% water keeps the flash point relatively high) for optimal EGT cooling and fuel economy. Some diesel owners use more methanol because power goes up with more methanol in the mix, (more than 100-hp increases with 75% methanol). However, it is generally not recommended, due to flammability issues.

Can You Substitute Windshield Washer Fluid as a Water-Methanol Mix?

Any fuel-grade methanol is good (available at most tracks and racing fuels dealers). As mentioned, blue winterblend windshield washer fluid is a good source, since you can get it for about $1.50 per gallon at Wal-Mart, and it contains a 30% methanol, etc. However, folks in warm-weather states, such as Florida, Arizona and Texas, will have to search hard for -20 windshield washer fluid.

What About the Detergent Commonly Found in Windshield Washer Fluid?

There is such a small amount (less than 1%), that it doesn’t seem to affect combustion. One of the drawbacks to windshield washer fluid is that it sometimes contains impurities that result in having to clean nozzle filters more often. Snow Performance offers Our Boost Juice®, which is a premixed source of clean, standardized 49% methanol.

Can Water-Methanol Injection Damage a Diesel Engine or Affect Engine Longevity?

With the advent of electronic controls and easy tuning, adding fuel to increase power in a modern turbo-diesel is easy. Adding too much fuel can cause dangerously high EGTs, especially during towing conditions in which high temps are prolonged. Water-methanol injection can be thought of as an insurance policy to guard against engine damage caused by high EGTs.

Damage from prolonged high EGTs can be acute (e.g. turbo impeller shaft failure) or chronic (exhaust manifold metal fatigue and cracking caused by heat’s effect on the silicon content of the metal). Towing is the perfect application for water-methanol injection, since it lowers EGTs and offers some semblance of peace of mind. However, as is the case with most tuners, there is a fine line at which too much fuel is too much, and EGTs get out of control.

Injecting too much water-methanol (which causes combustion quench) should be avoided, because it essentially “puts out the fire.” In actuality, mild quench is harmless. Most of the time when people think they have experienced “diesel knock,” it is actually quench they are hearing. The fix is easy. Simply put: Get out of the throttle and adjust your system to inject less. The benefits of a two-dimensional mapped controller (featured in the Stage-3 and MPG-MAX™ systems) include a more-correct injection quantity at all operating states, resulting in more power, easier setup and less propensity to quench.

Another key benefit of water-methanol injection is carbon removal from the tops of pistons, valves, intakes, variable-vane turbos (important with EGR-equipped vehicles) and EGR systems, resulting in a smoother-running engine and one that requires less maintenance (as in cleaning of the intake tract and EGR valve).

How Does Water-Methanol Injection Create More Horsepower and Lower EGTs?

Many people wonder how water can increase power, since it isn’t a fuel. Water increases power through two main mechanisms. First, it lowers charge air temps, which increases air charge density (more oxygen available for combustion). When water changes its state from a liquid to a gas, it absorbs heat. How much heat is absorbed depends on the total surface area of the droplets––which is why atomization is so important. Volume constant, the more finely atomized the droplets, the more total surface area.

Secondly, expansion takes place as the droplets change state during combustion, creating the “steam effect” that pushes down on the piston. This provides additional torque. Also, this is “safe power,” in that this torque is predominantly created as the piston is going down during the power stroke after TDC.

How Can Water-Methanol Injection Boost Fuel Economy?

More power is typically developed from a given amount of diesel. Simply put: The more fuel you ad to a diesel, the more power you make. Methanol is an additional source of fuel, and water adds power via the “steam effect.” You are replacing expensive diesel with inexpensive water or water-methanol. In fact, with a diesel pick-up, if you are using winterblend windshield washer fluid that costs $1.50 a gallon and diesel is at $4 per gallon, your net savings per 500 miles is approx $11.

If diesel goes to $5 per gallon (which, apparently, is just around the corner), the savings per 500 miles jumps to approx $17.50. To realize maximum fuel economy, water-methanol injection should take place at all engine load states and not just at high engine load states. This is the basis for the MPG-Max systems. These systems have the greatest range of injection (commands two nozzles independently and have special mapping that allows the correct injection quantity at all engine load states).

Installing a MPG-Max Water-Methanol System

Since the proof is in the pudding, so they say, we followed along as the team at Strictly Diesel installed a Snow MPG-Max water-methanol system on our cover truck, a `95 Dodge common rail with the 5.9-liter Cummins. With the stock turbo and stacked tuners, the truck was blowing a lot of smoke and was regularly hitting 1,400 degrees EGTs. The fix was to detune the truck by pulling the downloader and adding the Snow kit.

According to Snow Performance, its MPG-Max system can give up to a 20% increase in mps, reduce EGTs by 250 degrees and boost both horsepower and torque. The heart of the system is the trick digital controller that offers two-dimensional mapping and also features real-time boost and EGT readouts to eliminate the need for separate gauges.

The MPG system utilizes three nozzles, with one running the MPG side and the other two acting like carburetor secondaries when extra power under load is needed. A high-pressure (220 pis) pump provides both plenty of fluid and the correct atomization pressure. The system is fully adjustable and comes with a huge, 7-gallon tank. The system also comes with its own pyrometer and boost-reference fitting and allows the owner a myriad of adjustments to meet a particular driving style or need.

The installation is fairly straightforward, with the hardest operations being drilling and tapping both the intake and exhaust manifolds. The rest is a bolt-on deal that the average driveway mechanic can tackle. The highlights are outlined in the following photos. Strictly Diesel has a few shortcuts it uses for the install, including the company’s own unique boost fitting couple that makes the job easier.

So, how did it work? Once the owner of the truck got his overfueling situation under control, he reported a 250-to-300-degree EGT temperature drop under load and a 2 mpg increase––and he’s still playing with the settings for optimal performance.

If you tow a lot or just want to get added performance and reduced EGTs, look into Snow Performance’s new MPG-Max System.


Snow Performance



Strictly Diesel



Strictly Diesel’s Heavy-Duty Tank Mount

While Snow Performance’s 7-gallon strap-style mounts are adequate for most applications, Strictly Diesel has developed a more-secure mounting bracket for diesel enthusiasts who use their trucks off road or in competition. Strictly Diesel’s new water tank mount is fabricated from tig-welded mild steel tubing with a textured black powdercoat finish. The mount slides snugly over the 7-gallon tank and includes the necessary mounting hardware for a secure installation. Contact Strictly Diesel for more information: www.strictlydiesel.com or via phone: 623.582.4404

COMP-One System

The latest water-methanol injection system from Snow Performance is the COMP-One. According to Snow Performance, this system combines the company’s sophisticated water-methanol delivery system with an advance programmer that’s packed full of hot tunes for your diesel. The new unit features a dash-mounted monitor with customizable graphic options that can display real-time readouts, along with providing three distinct tunes that are especially created to work with Snow’s water-methanol system. For more information, contact Snow Performance at www.snowperformance.net or call 719.633.3811.

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