$0.00
What is Water/Methanol Injection?
In internal combustion engines, water injection, also known as anti-detonant injection, is a method for cooling the combustion chambers of engines by adding water to the cylinder or incoming fuel-air mixture, allowing for greater compression ratios and largely eliminating the problem of engine knocking (detonation). This effectively increases the octane rating of the fuel, meaning that performance gains can be obtained when used in conjunction with a supercharger or turbocharger, altered spark ignition timing, and other modifications.
Water injection is also used in some jet turbine engines, when a momentary high-thrust setting is needed, and in some shaft turbine engines, to increase power and fuel efficiency and improve pollutant emissions.
Composition of Fluid:
Many water injection systems use a mixture of water and alcohol (approximately 50/50), with trace amounts of water-soluble oil. The water provides the primary cooling effect due to its great density and high heat absorption properties. The alcohol is combustible, and also serves as an antifreeze for the water. The purpose of the oil is to prevent corrosion of water injection and fuel system components. Because the alcohol mixed into the injection solution is often methanol (CH3OH), the system is known as methanol-water injection, or MW50. In the United States, the system is commonly referred to as anti-detonant injection, or ADI.
Effects:
In a piston engine, the initial injection of water cools the fuel-air mixture significantly, which increases its density and hence the amount of mixture that enters the cylinder. An additional effect comes later during combustion when the water absorbs large amounts of heat as it vaporizes, reducing peak temperature and resultant NOx formation, and reducing the amount of heat energy absorbed into the cylinder walls. This also converts part of combustion energy from the form of heat to the form of pressure. As the water droplets vaporize by absorbing heat, it turns to high pressure steam (water vapor or steam mainly resulted from combustion chemical reaction), that would add engine output. The alcohol in the mixture burns, but is also much more resistant to detonation than gasoline. The net result is a higher octane charge that will support very high compression ratios or significant forced induction pressures before onset of detonation.
Fuel Economy can be improved with water injection, although the effect on most engines with no other modification, like leaning out the mixture, appears to be rather limited or even negligible in some cases. Some degree of control over the water injection is important. It needs to be injected only when the engine is heavily loaded and the throttle is wide open. Otherwise injecting water may simply drown the engine and cause it to quit. Direct Injection of water is possible. In a piston engine, this can be done late in the power stroke or during the exhaust stroke.
Use in Automobiles:
A limited number of road vehicles with large-displacement engines from manufacturers such as Chrysler have included water injection. Saab offered water injection for the Saab 99 Turbo. With the introduction of the intercooler the interest in water injection disappeared, but today, water injection is also of interest because it can potentially decrease nitrogen oxide emissions in exhaust. The most common use of water injection today is in vehicles with aftermarket forced induction systems, such as turbochargers or superchargers. Such engines are commonly tuned with a narrower margin of safety from detonation and hence benefit greatly from the cooling effects of vaporized water.
