Love Horsepower!

Do you Love Horsepower?

  • Increase font size
  • Default font size
  • Decrease font size

Water Injection Kit FAQ

E-mail Print PDF

How does water injection work?
The water injection solenoids are triggered by pressure switches. These pressure switches are key'd off of the intake manifold (boost pressure) via a silicon air tube included with the kit.  At certain boost pressures the solenoids will turn on and spray water through nozzles located in the intake into the engine. The nozzles are usually located after the intercooler and before the throttle body.
As boost pressure rises, there is a larger tendency for the engine to knock. So, as boost is rising, you inject water which effectively increases the octane level of the fuel and hence reduces the chance of detonation. More boost pressure can then be run.
The water reduces detonation by lowering the charge air temperature (temp of the air going into the engine) by having it phase change from a liquid to a gas before it reaches the combustion chamber. Water has a very high latent heat of evaporation - that is,  it takes a large about of energy (heat) to change water from a liquid to a gas.  Some of the water (hopefully) will also reach the combustion chamber in liquid form. During the combustion process this reduces the combustion temperature, and hence reduces the chances of detonation.
End result, with water injection you can run more boost without detonation, and get an added benefit of removing carbon buildup.

I'm afraid water may cause internal engine rust - is this true?
Absolutely not!  You do not need to be concerned about rusting the engine from the inside out. No water will be inside the engine when the engine is shutoff. Any water that is injected is immediately turned to steam either before it reaches the combustion chamber, and certainly after it gets there!  It then exits the engine with the rest of the exhaust.

Does the kit include a reservoir tank?
The kit does not include a reservoir tank.  The reason for this was that the user may want a specifically shaped tank for their application.  Some users will want a fancy tank, others will be fine with a junkyard windshield washer tank.  Windshield washer tanks with level sensors can be found at most junkyards.

How much better is the stage two kit?
The stage 2 kit offers better control over the amount of water injected since there are 2 stages instead of 1. At lower boost pressures a lot of water is not desirable, but some is.  At higher boost pressures more water is desirable.  If too much water is injected at low boost pressure, it may cause the engine to hesitate/stumble - if not enough water is injected at high boost, the engine may detonate depending on how much boost/advance you are running.  To solve this, two stages can be used. The first stage being a smaller nozzle and injecting at lower boost pressure; the second stage being a larger nozzle injecting at a higher boost pressure. On my own car, I use a 3GPH and 10GPH nozzles for the two stages.

Does water injection work for normally aspirated cars?
Water injection can benefit NA engines, but not to the extent that it can forced induction engines. You may be able to run more timing advance on an NA engine with water injection and hence get more power. You will also benefit from the cleaning properties of water injection as it will remove carbon buildup on the pistons.  In this kits current form it will not work correctly with a normally aspirated engine.  This is due to the pressure switches.  A future 'stage 3' kit it being considered which will use electronics to switch on/off the solenoid valves.  This controller could be tied to either boost pressure, or throttle position for NA applications.

What is the difference between this kit and the Aquamist 1S?
The main differences are:

  • This setup uses a high pressure pump (100psi) with a significantly higher flow rating (about 10 times!), and is inexpensive to rebuild. Consequently the pump can support many nozzles, as well as future expansion - for example an intercooler mister, brake, or radiator mister.

  • The setup here uses an accumulator to lengthen pump life. During street use, the pump will run very infrequently which leads to significantly longer pump life.

  • This design uses a solenoid valve. Water is pre-pressurized behind the solenoid which is physically located close to the intake. When the solenoid(s) open, pressure is already available to the nozzle. There is no need to wait for the pump to spin up, and pressurize the line all the way from the pump to the nozzle.

  • This kit includes LEDs to monitor solenoids and pump activation.  This adds in tuning the system.

  • System pressure is easily measured using a standard tire pressure gauge.

  • This kit is more affordable and better!

Why is this kit better than the Aquamist 1S?
This setup has many advantages over the Aquamist kit, and is designed for ease of use, effectiveness, and longevity. Since an accumulator is used, the pump runs very infrequently leading to longer pump life. In the unlikely event that the pump does fail, an inexpensive rebuild kit is available. The pump has a higher flow rating and consequently the setup is easily expandable - for example adding additional water injection nozzles, intercooler mister, brake, and radiator mister etc.. The Aquamist pump can very quickly run out of flow if more nozzles are added; the pump included with this kit has nearly 10 times the flow rating of the Aquamist pump.  Since solenoids and an accumulator are used, high pressure is immediately available to the nozzle as soon as the solenoid opens (instant on - no waiting for the pump to build pressure).  The dual nozzle setup provides better water flow control than the Aquamist 1S setup, and is still more affordable.  See "How much better is the stage two kit" above.

Can you use methanol with this kit?
Yes - but only up to 50%. The seals in the pump are Santoprene and the valves are Viton. Santoprene is resistant to methanol, but the Viton will start to expand with exposure to anything more than a 50% mixture. The aquamist pump can also run up to 50% mixture of methanol according to their site.  To see what you can run check out santoprene and viton.

Quick installation run-down.
The installation involves mounting the pump, accumulator, solenoids, and pressure switches. You need to drill and tap a 1/8"NPT hole(s) into the intake plumbing for the water injection nozzles. The tap is not included in the kit, but is available from Sears and other hardware stores.  The wiring is pretty straight forward and includes connecting the pump to switched +12 volts and ground, and wiring up the LEDs, pressure switches, solenoids and master switch. A wiring diagram is included in the instructions. The pressure switches have to be plumbed into the intake for a vacuum sense, but everything to do that is included in the kit.

How big should the water tank be?
It depends on your application.  For most applications, a 1 gallon reservoir will be sufficient.  If you are injecting more water and/or participating in road racing or any other modes of operation where extended boost is used, then a larger tank will be required.  The trade off is weight.  So really take into account what you will be using the car for.  Certainly if it is for road racing, you want enough water to last the race, and no more.  For street applications, and/or moderate to light use of boost, a 1 gallon tank may only have to be filled once per fuel fill up.

What if I run out of water?
The Shurflo pump included with the kit can run for a very long time without water.  Having said that, it is best to turn off the pump if no water is currently available.  If your car's engine is tuned to the point where it depends on water to prevent engine damage, you will certainly want to install a tank that includes a level sensor, or install a water pressure gauge in the cabin area.

How can I measure the system pressure?
The system pressure can be measured in two ways.  The simplest approach is to unscrew the nipple on top of the accumulator.  There you will find a standard tire valve.  Using a tire pressure gauge the system pressure can be checked.  It is important to not let air out of the accumulator.  If too much air is let out, you will have to purge the system.  The other method is to plumb in a water pressure gauge, and run the gauge into the cabin.  This method is only advisable if you are running straight distilled water.  You do not want to have any flammable liquid coming into the cabin area!

Where along the intake track should I install the nozzles?
For most installations the water injection nozzle(s) should be place immediately after the intercooler, if one is installed.  Unfortunately, there is no formula for where the best location should be.  If you have no intercooler, the nozzles should be placed as far from the throttle body as practical.  This give the water more time to change state from a liquid to a gas.  This state change is what removes a large amount of heat.  The same is true if you have a particularly inefficient intercooler.  Having said all that, there is a large benefit to having water in liquid form reach the combustion chamber as it will substantially reduce the combustion temperature and hence slow the combustion process and the tendency to knock.  This is similar to how a higher octane fuel works.  The higher octane fuel actually burns slower than lower octane fuel.
The best advice here is to try the nozzles far from the throttle body, and after the intercooler.  If there is still detonation, try a location closer to the throttle body.  Under no circumstances should the nozzles be placed before a turbocharger.
For superchargers, the nozzles can be placed before the supercharger.  This may actually improve supercharger efficiency as it lessens the space between the rotors.

How much alcohol should I mix in with the distilled water to avoid freezing in the winter months?
This depends marginally on which alcohol you are using.  The following table shows some values for methanol; ethanol alcohol is similar.  Do not run more than a 50% by volume mixture of distilled water and alcohol as it may cause the pump seals to swell.  Remember that the temperature of an attached garage will tend to be warmer than the outside temperature.  Denatured alcohol can be purchased at most local hardware stores.

Methanol Water Mixture by Volume Freezing Point Degrees F (Degrees C)
0 32 (0)
13% 20 (-7)
24% 0 (-18)
35% -15 (-26)
46% -40 (-40)


Last Updated on Saturday, 01 January 2011 15:51