How It Works and FAQs
The main benefits of water injection are:

1. Will significantly help to prevent detonation.

2. Will raise the octane of the gas you are using.

3. By reducing detonation, this will allow you to increase boost or run lower octane.

4. Lowers air intake temperatures which keeps the engine cooler from the inside out.

5. Will literally steam clean the carbon deposits from within the engine.

What is Water Injection:

Water injection systems are predominantly useful in forced induction (turbocharged or supercharged), internal combustion engines. Only in extreme cases such as very high compression ratios, very low octane fuel or too much ignition advance can it benefit a normally aspirated engine. The system has been around for a long time since it was already used in some World War II aircraft engines, which allowed them to produce more power and therefore fly at higher altitudes.

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.  Detonation, an effect also known as engine knock or pinging, occurs when the air/fuel mixture ignites prematurely or burns incorrectly. In normal engine operation the flame front travels from the spark plug across the cylinder in a predefined pattern. Peak chamber pressure occurs at around 12 degrees after TDC and the piston is pushed down the bore.

In some cases and for reasons such as a poor mixture, too high engine or inlet temperatures, too low octane fuels, too much ignition advance, too much turbo boost, etc.,  the primary flame front initiated by the spark plug may be followed by a second flame front. The chamber pressure then rises too rapidly for piston movement to relieve it. The pressure and temperature become so great that all the mixture in the chamber explodes in an uncontrolled manner. If the force of that explosion is severe some of  the engine's moving parts (pistons, rods, valves, crank) will be destroyed.
Detonation, in any engine, should always be avoided by either lowering inlet temperatures, using higher octane fuel, retarding ignition (hence lowering engine output), lowering engine blow-by (a situation in which high crankcase pressure sends oil fumes back inside the combustion chamber), running the engine a little richer than at the stoechiometric ratio, lowering the compression ratio and/or boost pressure, ... .
Water injection is used to lower in-cylinder temperatures and burn the air/fuel mixture more efficiently thus helping avoid detonation.

In high pressure turbocharged engines the air/fuel mixture that enters the cylinders can, in some cases, explode prematurely (before the spark plug ignites) due to the extreme engine environment conditions. This situation is extremely destructive and results in severe engine damage (piston piercing). To avoid damaging the engine by detonation or pre-ignition phenomena, 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 detonation or pre-ignition but also provides additional inlet air cooling and, hence, denser air. The sole functions of water injection is avoiding detonation by lowering air charge/cylinder temperatures along with increasing the effective octain of the air/fuel charge, so the ECU can advance timing and take advantage of the increased boost.

There are mainly three variations of water injection systems. They are dependent of 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 then used as coolant (i.e. is not burned) and runs the engine above the stoechiometric ratio (i.e. rich).

Frequently Asked Questions

Will water injection increase my horsepower?

Yes, but not directly. Water injection works to eliminate detonation, also known as knock. The big gains come from the ability to increase boost as well as the full ignition advance allowed by the ECU when it does not detect knock. While the cooling of the intake charge will produce some power increases, those increases are cancelled by the charge space occupied by the water vapor. In other words, there is slightly less room for air and fuel. However, by using up to 50 percent alcohol with the water, additional cooling takes place before the turbo, and the alcohol works as a fuel in the charge. This results in an increase in power.
Is water injection new?

No. Water injection was used during WWII to suppress detonation in fighter aircraft and increase their service ceiling.

What size injector do I need?

Every engine is unique, however the general formula is 1.0 - 2.0 gallons per hour (gph) per 100 horsepower.  It is recommended to start on the lower end, and then increase from there if needed.  Keep in mind when buying or building a two stage system that both injectors are running when at high boost, so your total flow is the rating of each injector added together. 

Does the water "burn" in the engine?

No. The water simply converts from a vapor to a gaseous state which absorbs huge amounts of heat, due to the energy required to transform it.

What if my engine has an intercooler?

Most turbos do.  Just install the nozzles right after the intercooler.  We do not suggest injecting water before the turbo in an intercooled application, as most of the water will condense out at the intercooler.  Also, alcohol and aluminum react when together.

Do I need an extra "tank" for the water?

Not necessarily.  The systems are designed to use the original washer fluid tank (most have a built in level sensor), but you may choose to add a separate tank which you supply if you need something larger.

How often do I need to fill the tank?

It all depends on how often you use the system (it's only active under boost) and how big the tank is. Even the smallest tanks will last for 8 full 1/4 mile runs or so. In around town driving (agressive driving) a windshield washer tank that is a gallon in size should out last a tank of gas.

I have both of the hard pipes, the uppipe from the intercooler and the one from the airbox to the turbo.  Where is the injector to be installed that would be the most efficient?  Should it be installed in the pipe just before the turbo/throttle body or in the uppipe?

The injectors should most definitely be placed in the uppipe.  If they are before the intercooler, it will eventually fill it with water, not allowing air to pass, or at the very least restricting it.

I have Stage 1, the AGP WGA, and I plan to install the diode to clamp the map sensor (conservatively).  I don't plan on getting a boost controller at this time.  Does this have any bearing on which kit that I should purchase?  Which kit would you recommend?

No.  However, the purpose of water injection is to keep the compressed air temperatures down, eliminating the need for the clamp.  This way, your computer still has total control over the engine, just incase something fails. 

Is a 100 psi pump enough?  I see that the ones on Ebay are 140 psi.

The 100 psi pump is more than enough if you are running less than 20 PSI of boost.  If you put out more than 20 PSI, then you must have the 150 PSI pump so the injector nozzles are pressurized enough for a completely atomized mist (pump pressure fights boost pressure).  The 150 PSI pump produces an extremely fine mist.  The more pressure the pump puts out, the finer, and more atomized the mist.  The more atomized the mist, the more surface area a given amount of injected water has, and therefore getting better results.

Is the nozzle brass, high grade, and can it be installed on the outside of the pipe?

The nozzle is brass, definitely high grade, with a filter that is removable.  As for mounting it, the other company sells this fancy sound nozzle set up, which I bought, and all it does is take up space in the uppipe, preventing airflow.  The way I have them mounted now is just the injector head is on the inside of the pipe, which is only about the size of the tip of a Q-Tip.

Is there a high current relay switch?

Yes.  There is a 30 amp relay switch.  The relay and harness comes with all the kits, or is available separately for $7.99.

Is there an adjustable pressure switch for boost activation?  Or is it pre-set for our Stage 1 boost levels if I don't have a boost controller and a boost gauge?

The pressure switch is adjustable from 1-25 psi.  It takes a simple allen key to adjust the pressure, which is included with all of our kits.  It comes preset to about 10 psi.  The Vari-Cool Controller is adjustable with a start point as low as 1 psi, and a maximum point of as high as 30 psi.

Does the kit include the wire needed, and what gauge is the wire?  Are there crimp terminals for wire hookups and a fuse assembly?

They will include red and black 14 gauge wire along with insulated crimping connectors and an inline fuse.

Any recommendations about the placement of the pump?  Someone on  the forums said that there would be one place under the hood where it could be mounted.  Or do you prefer another location, and why?

Every car is different.  On our car, we mounted the pump in the area available where the hood cowling meets the windshield.  Another common place is inside the front bumber.  The closer to the engine the better/easier/cheaper.  If you need to/want to mount the pump in the trunk, there are no problems with this as the pumps are plenty strong enough to draw, and pump, any length that any car/truck could possibly have.  The only difference with mounting the pump far from the engine is the extra wiring and tubing that will be required.  Although not required, it is recommend to mount the pump lower than the tank, so if you do run the tank dry, priming is much quicker this way.

Is there a way to tell when the injection system is working?

There can be.  All of the Stage 2 Kits have the clogged nozzle/flow detector switch.  It is a pressure switch (solid brass and rated at 250 psi) that is placed between the solenoid and the injector.   When the system activates and the injector is pressureized, the pressure switch will trigger and illuminate a small led light (included in all Stage 2 kits), which is usually mounted in a gauge pod.   Also, when you let off the gas, the pressure should bleed off, therefore the light will go out.  The light should go out immediately, but if the injector is clogged, the pressure will remain between the water solenoid and the injector, and the light will stay on, telling you there is a clogged injector.  There is one detector per stage, so dual stage systems will have two.

Here are some interesting facts:

1. Maximum Torque occurs at a 13.2:1 Air Fuel Ratio.
2. Transitional Fueling and Maximum Boost Air Fuel Ratios are about 12.5:1.
3. Water Injection is most efficient with a 50/50 water alcohol mixture.
4. Methanol is the most common and best alcohol to use if you will be using an alcohol/water mixture.
5. Denatured (will eat your pump in 2 months and is not covered by warranty) alcohol, typically 95%, is cheap and is available in paint, hardware, and Home Depot type stores in gallon containers for about $10.00. Isopropyl alcohol can be used but it is often 30% or more water by content.
6. Water Injection allows ignition timing to be more aggressive.  In other words boost does not automatically mean pulling your timing.
7. Excessive amounts of ignition retard will cause a loss of power and overheating.
8. Water to Fuel ratios should be based on weight and not volume. 
9 . Water weighs 8.33 lb per gallon.
10. Alcohol weighs 6.63 lb per gallon.
11. Air weighs .080645 lb per cubic foot. It takes about 150 cubic feet of air per 100 horsepower. It takes about 12 lb of air per 100 horsepower.
12. Water or Water / Alcohol to Fuel Ratios are between 12.5% to 25%. This means Air to Fluid Ratios are between 11.1:1 and 10.0:1 with water injection, when your fuel system goes into closed loop (ie. when you floor the throttle).
13. Maximum water delivery should be in higher load scenarios, such as when torque is highest.
14. Atomization of the water mixture is directly related to it effectiveness. Finer droplets cool the inlet charge better and with less mass they navigate the inlet plenum easier for more equal water distribution.
15. Don’t flow water through an intercooler.
16. Atomized water, just like fuel , does not like to make turns thus making accurate distribution something to think about. This is why port fuel injection is the norm. Water is a fluid just like your fuel. Multiple nozzles, equally spaced in the plenum, although it complicates things, is a superior design.
17. The introduction of water will allow higher boost pressures to be run without detonation. Higher pressures will increase torque. It’s always about torque.
18. Racing high octane gasoline should be used for all forms of competition and for higher than normal boost levels if possible. Water injection as well as charge cooling (intercooler) should be used with racing gas when used for competition.
19. Fuel Injectors should not be used to deliver the water in a water injection system since they are more susceptible to corrosion.
20. Progressive controllers which vary the voltage to control pump pressure should not be used.  This can cause the pump to stall, meaning it is powered, but not pumping.  Our Vari-Cool controller always gives the pump full voltage.  In the patent for Shurlfo pumps, they specifically address this problem, stating the problems that can occur if supplied less than 12 volts.  If another company claims that varying the voltage is not an issue, ask them to provide the documentation that claims this.
21. Fuel Injection pumps cannot be used for water injection. Water is conductive. Gasoline is not. Water will corrode an efi pump shut in a very short period of time.
22. Water injection has a cooling effect on the engine head, valves, and cylinder. Exhaust temperatures (EGT) can be reduced from 50 to 150 degrees Celsius.
23. The cooling of potential hot spots in the combustion chamber defeats pre-ignition, the most destructive form of uncontrolled or unplanned combustion.
24. Higher static compression ratios will require a higher percentage of water or water / alcohol.
25. No, water does not burn. We are not combusting the hydrogen in the H2O.
26. At around a 13.2:1  air/fuel ratio, exhaust gas temperatures will peak.
27. Ferrari suspended water in their fuel during their 1980’s Formula1 period. We don’t recommend that you try this...although Acetone will mix with water.
Can I use Washer Fluid?

Some engines get the best gains from straight water, and some with straight methanol, and some with a water/methanol mix.  How much methanol, well that is up to what your engine prefers, and every engine is different.  We recommend to start with straight water, and then see the results.  Then, try a 10% meth/water mix, being sure to purge the straight water from the lines, and then see the results.  Do this for 20%, 30%, 40%, and 50%, etc....  If during this process, you notice your performance decrease, then don't try any higher of a mixture.  Revert back to the previous amounts and use what works best. 

There are many places to buy straight methanol, found here, but if you are going to use a water/methanol mixture, the easiest (and cheapest) is to buy the blue windshield washer fluid that is used during winter time to prevent the fluid from freezing.  It may sound cheap ($1.29-$1.99 per gallon), but it is just as good as any methanol/water mixture you would make otherwise.  The blue is just a dye, and an extremely insignificant amount (<1%).  Some of the washer fluids, such as RainX, contain cleaning additives, but this is easily determined by shaking the bottle and seeing of it suds up like soapy water.  If it does, don't buy it, but if it doesn't, then it is good to use.  There are many different brands out there, but they all have common amounts of methanol for their respective temperature rating, regardless of the brand.  We have many MSDS's (Material Safety Data Sheets) from different companies to support the following data, but only one per temperature rating is available for viewing, which is representative of all the brands (within a few percent) that produce that specific temperature rating.  To view the MSDS, simply click on the item.

+20 F Washer Fluid  -  Contains approximately 7% methanol.

0 F Washer Fluid  -  Contains approximately 23% methanol.

-10 F Washer Fluid  -  Contains approximately 28% methanol.

-20 F Washer Fluid  -  Contains approximately 35% methanol.

-25 F Washer Fluid  -  Contains approximately 38% methanol.

-50 F Washer Fluid  -  Contains approximately 62% methanol.