CharlieGSanD

this is not the only way to build a water injection system. id reccomend doing some more reasearch before attempting to install one in your car

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Water injection systems are only needed in turbo charged engines. The system has been around for a long time since it was already used in some World War II aircraft engines.

A water injection system works similarly to a fuel injection system only it injects water instead of fuel. Water injection is not to be confused with water spraying on the intercooler's surface, water spraying is much less efficient and far less sophisticated.
A turbocharger essentially compresses the air going into the engine in order to force more air than would be possible with the atmospheric pressure. More air into the engine means automatically more fuel has to be injected in order to maintain the appropriate stoechiometric value of the air/fuel ratio (around 14:1). More air and fuel into the engine leads to more power. However by compressing the inlet air the turbocharger also heats it. Higher air temperatures lead to thinner air and therefore an altered stoechiometric ratio which can lead to a lean mixture and detonation. In high pressure turbocharged engines the air/fuel mixture that enters the cylinders can explode prematurely (before the spark plug ignites, effect also known as engine knock) due to the extreme engine environment conditions. This situation results in severe engine damage (piston piercing). To avoid damage to the engine, water is injected, along with fuel, in the combustion chambers in order to provide a water/air/fuel mixture which not only burns more efficiently and avoids spontaneous detonation but also provides additional inlet air cooling and, hence, denser air. There are mainly three variations of water injection devices. They are dependent on the location of the water injectors. The first technique consists of injecting water at the entrance of the intake manifold. The second injects water at the exit pipe of the intercooler. The third technique injects water at the entry of the intercooler and is only used in competition vehicles. In this latter variation most of the in-cylinder detonation prevention is done by injecting additional fuel which is used as coolant (i.e. is not burned).

How water injection works

The system, usually, is made up of 3 elements:

A water injector (similar to a fuel injector)

A high pressure pump (capable of at least 3 to 4 bar pressure and sometimes even more)

A pressure sensor connected to the inlet manifold

An inlet air temperature sensor

Usually a water injection system is engaged when the inlet air temperature is exceeding a certain value, typically 40 degrees Celsius, and the engine is on boost. The most advanced systems add to the above electronic circuitry that provides 3D cartography similar to what is used in fuel injection systems. Cartography based devices take into account many more parameters such air/fuel ratio, throttle position and so on.<ul><li><a href="http://www.dawesdevices.com/howto.html">http://www.dawesdevices.com/howto.html</a</li></ul>

CharlieGSanD

<ul><li><a href="http://home.ccci.org/Key_Information/2ndWaterInjection.htm">http://home.ccci.org/Key_Information/2ndWaterInjection.htm</a</li></ul>