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Home MR2 Turbo Do It Yourself / Projects Joe's Water Injection System

Joe's Water Injection System

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Joe’s Water Injection System

Installation Instructions


This system is designed for ease of use, effectiveness, and longevity. I hope you will enjoy installing this system as much as I have enjoyed designing it. Please do not expect water injection to give you great power gains in of itself, however, do expect to be able to run more boost pressure, and more ignition advance safely. There is no reason to install a water injection system without the intention of increasing boost pressure and or advancing ignition timing.

Parts needed - see the parts page for more details on where to purchase the parts and exact part numbers.

  • Shurflo 100psi pump model 8000-543.
  • Shurflo accumulator model 181-203.
  • Two 150psi solenoid valves
  • 1 toggle switch
  • 3 LEDs, green, red, and yellow
  • 3 nozzles, M1, M3, and M5.
  • ¼ inch nylon tubing
  • Rubber hose (for pressure switches)
  • 2 T adapters.
  • Wiring hardness, 4 conductor wiring, and connectors.
  • Total of 16 brass fittings.
  • Sheet metal screws for mounting pump and accumulator
  • Metal screws for mounting solenoids and switches.


The components required:

Complete Stage Two Kit


This kit is designed to be easy to install, but still requires that the installer be able to solder wire connections, and drill and tap for the nozzle(s) installation. For safety sake, before performing the wiring work, please disconnect the negative terminal on the battery. The general layout of the water lines is shown in the following diagram.

Figure 1 - Water Line Diagram


Determine locations for water injection components.

The location of the various components of the water injection kit must be determined. The pump/accumulator unit must be installed in a position that is relatively near the tank. The tank outlet should be at a higher elevation than the pump inlet. The solenoid(s) can be located as far from the accumulator as necessary. They should be placed as close as possible to the water injection nozzle(s) in order to keep the nylon pipe length from the solenoid outlet to the nozzle as short as possible. The short pipe length (nylon tubing) from the solenoid to nozzle ensures that the water will flow as soon as the solenoid opens. The solenoids should be mounted firmly and in a relatively cool location in the engine compartment. They can be mounted with the included screws. In most installations the nozzle should be located after the intercooler if one is installed. Do not install the nozzle before the turbocharger inlet! In some cases it may be beneficial to place a nozzle before the intercooler inlet, but only in a multiple nozzle kit. In most cases the most benefit of water injection will be seen with the nozzle(s) located after the intercooler and before the throttle body. A sample installation of two nozzles is shown along with the solenoids. Both nozzles are located immediately before the throttle body, and the nylon tube length from the solenoids to the nozzles has been kept short.

Figure 2 - Nozzle and Solenoids Sample Installation.

Nylon tubing will be required to run from:

  • The tank to the pump inlet.
  • The accumulator outlet to the solenoids, and
  • The solenoids to the nozzles.

Each solenoid will require a chassis ground connection. The pump will require an ignition switched +12Volt source and a chassis ground. The pressure switches need to be located in a position that is near a vacuum source.

Once the location for the pump/accumulator, solenoids, pressure switches, and nozzles has been determined, the locations for the ‘cabin’ components are next. These components include the LEDs, and master on/off switch. The switch will require an ignition switched +12Volt source, and each LED will require a chassis ground. For the two-nozzle setup, a total of four wires need to be run from the cabin area to the engine compartment. Three wires will be required for the single nozzle setup. Locate the position of the LEDs so that they are visible from the driver’s seat. The LEDs will indicate:

  • Solenoid one active [Green]
  • Solenoid two active (if installed) [Red]
  • Pump currently on. [Yellow]


On any fitting that is a ‘threads to threads’ fitting, and not a compression fitting, sealant is required. The sealant is placed on the threads and can be Teflon tape or a paste Teflon sealant.

Pipe Fittings

Please note that all the fittings used in this kit are pipe fittings. When connecting pipe fittings together they become tight quickly. This is because the threads have a taper to them that allow them to seal very effectively. Please be extra cautious when connecting a metal fitting to a plastic one. Do not cross thread!


Pump and Accumulator Installation

The Shurflo Accumulator contains a bladder on one end and free air space on the other, and has been pre-charged to 40psi. The best pressure for this application is 50psi, although 40psi is also sufficient. A tire pump can be used to pre-pressurize the accumulator to 50psi before installation. A typical tire pressure gauge can be used to check accumulator pressure. When the system is operating, and the pump has pressurized the accumulator, the pressure at the accumulator should be between 80psi and 100psi. The accumulator serves two purposes.

1. To allow the system to maintain full operating pressure with the pump off so that when the solenoid valves open, immediate pressure will be available.

2. To lengthen the pump’s life by acting as a ‘buffer’ so that the pump doesn’t have to continually cycle on and off with each opening and closing of the solenoids. In fact, you will notice the pump running very infrequently during normal driving.

Before installing the pump and accumulator into your car, they need to be pre-assembled. Using the fittings shown in figure 3 connect the pump and accumulator together as shown in figure 4.

Figure 3 - Pump and Accumulator Fittings

Figure 4 - Pump and Accumulator with Fittings

Use the left most fitting in figure 3 to connect the nylon tubing to the water tank, and use the right most fitting to connect to the solenoids. The three center fittings connect the pump and accumulator together. On the pump and accumulator, be careful not to cross thread the brass fittings onto the plastic threads and use sealant on all threads. A pre-assembled accumulator and pump is shown in figure 5. Please do not forget Teflon tape or some sort of pipe sealant on the threads!

The accumulator should be pressurized to 50psi before installation. The accumulator is not shipped at 50psi because the pressure may damage the internal bladder when no water is present. See ‘Purging the System’ at the end of this manual.

Figure 5 - Pre-assembled Accumulator and Pump

Run the nylon tubing from the accumulator into a ‘T’ fitting and then into the solenoids. Do not forgot to use the brass nylon tube supports when installing any compression fitting. Depending on your installation an elbow fitting may be required. See figure 6 for a sample installation. Do no install the solenoids at this point.

Figure 6 - Sample Solenoids and 'T' installation.

Install the pump and accumulator using the provided sheet metal screws, or by any other means necessary to firmly mount them into place. The pump can be mounted in any position, but if mounted vertically, be sure to mount it with the pump section facing down.

A sample installation is shown.

Figure 7 - Sample Pump and Accumulator Installation

Nozzle Installation


The nozzles are installed using two separate fittings in addition to the nozzle itself. Once the location for the nozzle has been found, drill and tap a hole using a 1/8 inch NPT (national pipe thread) tap. If you do not currently have such a tap, one can be purchased from a local hardware store or Sears. This kit uses brass compression fittings for all connections to the water line.

For the nozzles, use the ¼” to ¼” female compression fittings and the ¼” to 1/8 inch male pipe bushing. This is shown in the following picture. Notice the nozzle has an M5 stamped into it. This indicates the flow rate for the nozzle, in this case 5GPH at 100psi, or 315.45cc/min. To convert from gallons per hour (GPH) to cc/min, multiple GPH by 63.1.























Table 1 – Gallons Per Hour to Cubic Centimeters per Minute conversions.

Figure 8 - Fittings For Water Injection Nozzle Installation.

From left to right is the ¼” to ¼” couple, the male pipe bushing ¼” to 1/8”, and the water injection nozzle.

Screw in the water injection nozzle from the inside of the pipe through the tapped hole. Install the male bushing (center of above picture) onto the threaded end of the water injection nozzle. Then install the compression fitting onto the bushing. A sealant should be used on the pipe threads. Cut a piece of nylon tubing that is long enough to reach from the nozzle to the solenoid. Install the tubing into the nozzle side using the compression fitting as shown in the following figures 9 through 11.

Unscrew the fitting.

Figure 9 - Water Injection Compression Fitting.

Install the tubing by pushing the nut onto the tube and then install the tube insert (center of above picture) into the end of the nylon tube as shown in the following figure. Please note that the included brass tube supports (above center) need to be used for any fitting that attaches to nylon tubing.

Figure 10 - Compression Fitting Installation.

Figure 11 - Compression Fitting Installation

The completed nozzle assembly is shown in figure 12. The nozzle, of course, will be located inside an intake pipe when installed on your engine (see figure 1). Tighten the compression fitting enough that you cannot pull the nylon tubing from the fitting by tugging on it by hand. Do not over-tighten the fitting. Keep in mind that it does in fact have to compress the metal onto the brass tube support to create a leak free seal. A wrench will be required.

Figure 12 - Water Injection Nozzle and Fittings.

Sample two-nozzle installation is shown.

Figure 13 - Sample Nozzle Installation

Solenoid Installation

A high quality 150psi metal-bodied high-speed solenoid valve is used in this kit. Install both compression fittings into the solenoid valve before installing the valve into the engine compartment as shown.

Figure 14 - Solenoid and Compression Fitting.

Notice the In and Out markers on the solenoid. Be sure to connect the In side of the solenoid to the accumulator, and the Out side to the water injection nozzle. Depending on your choice of location for the solenoid it may be best to install the tubing from the nozzle to the solenoid, and from the accumulator to solenoid, before screwing it down in the engine compartment using the supplied metal screws. Cut tubing, of appropriate length, to run from the ‘T’ fitting to the solenoids and install it into the compression fittings. When screwing down the solenoids be sure not to run the screws into the body of the solenoid valve. See Figure 5 for a sample installation.


Locate the following pickup points for your installation:

  • 12 Volt Ignition Switched Source in the Engine Compartment.
  • 12 Volt Ignition Switched Source in the Cabin.
  • Chassis Ground in the Engine Compartment.
  • Chassis Ground in the Cabin.

Install the long, grey, 4-conductor wire from the cabin area into the engine compartment to a location near the solenoids and pressure switches. Cut the wire to an appropriate length. Make sure to keep the wire away from high temperature sources. Zip ties can be used to hold the wire in place. Strip some insulation from each of the 4 colored wires and install the supplied bullet connectors. Connect the bullet connectors to the solenoids and pressure switches using the supplied harness, and make sure to connect to the same colored wires. In other words connect red-to-red, green-to-green and so forth. The function of each wire is:

Red: 12 Volt ignition switched power from the supplied toggle switch.

White: Pump is currently running.

Green: Solenoid 1 is currently spraying.

Black: Solenoid 2 is currently spraying.

Pressure Switches Installation

The pressure switches should be mounted in a cool location in the engine compartment near the solenoids. The included wiring harness (you'll have to build your own!) is used to connect the pressure switches to the solenoids, the solenoids and pump to the LED indicators, and power from the toggle switch to the pressure switches. Each pressure switch has three connections on it. Do not use the NC (normally closed) connector on the pressure switches. Connect the red connectors to the COM connector on the pressure switches and the blue connectors to the NO (normally open) connections as shown in the following figure. If blue connectors were not supplied connect the thick black wires to the NO connections.

Figure 15 - Pressure Switches and Wiring Harness

Mount the pressure switches with the included screws or via some other means. Locate a vacuum source (usually on the intake manifold) to use as the pressure sense. Using the included air T connectors and rubber tubing connect each pressure switch to the vacuum source.

Figure 16 - Pressure Switch Connections

Power Switch Installation

In the cabin area install the supplied toggle switch by connecting one end of the switch to an ignition switched source (it does not matter which end you choose). Connect the other end to the red wire contained in the 4-conductor wire leading to the engine compartment.

LED Installation

Install the supplied LEDs by connecting each of the black wires from the LEDs to a chassis ground in the cabin area. Depending on the location you choose for the LEDs, it may be best to connect all the LED black wires together first, and then run a single wire to a chassis ground. Connect the color LED you would like for each function to the appropriate colored wire in the 4-conductor wire leading to the engine compartment.

For the LED color you wish to use for ‘Pump On’ connect the red LED wire to the white wire. The LED color you wish to use for ‘Solenoid 1 On’ connect the red LED wire to the green wire and finally for the LED color you wish to use for ‘Solenoid 2 On’ connect the red LED wire to the black wire. For these connections you may or may not choose to use connectors. Be sure to solder all connections and insulate them appropriately. For the included wiring harness use the included snap plugs as shown in the following figure. You may solder the connections (recommended) or insert a stripped wire and compress the plug (small end) onto the wire with pliers.

Figure 17: Snap Plugs and Wiring Harness.


Power/Ground Connections for the Pump and Solenoid

Connect each solenoid (the remaining free wire on each solenoid without a connector attached) to a chassis ground in the engine compartment. Connect the black wire from the pump to the same or other chassis ground. Finally connect the red wire from the pump to an ignition switched +12 volt source. The white wire attached to the pump connects to the white wire in the 4-conductor wire leading from the cabin area into the engine compartment. A complete wiring diagram is shown in figure 18.

Figure 18 - Wiring Diagram


Testing The System

Once the installation has been completed, it should be tested before use. Fill the tank using distilled water or a distilled water alcohol mixture. Do not exceed 50% methanol to water mixture as the pump seals may be damaged. For testing it is recommended to use distilled water only. Turn the ignition switch to the on position, but do not start the car. The pump LED should immediately light and the pump should run until full system pressure is reached (100psi). This should take approximately 20 seconds to fill and pressurize the accumulator. You can test the system pressure using the nozzle on top of the accumulator. Unscrew the nozzle, and use a standard tire pressure gauge to test the system pressure. Try not to allow air to escape. If too much air escapes, you will have to purge the system (see below).

If this works as expected, check for leaks, and then test the solenoids. Turn the toggle master toggle switch to the on position. With the nozzles visible, and not attached to the engine, or in such a way that water will not flow into the engine, use a test connector or alligator clip to manually connect the NO and COM connections on one of the pressure switches. The solenoid should then open and the system will purge itself of air, and water should flow out of the nozzle. The indicator LED for this solenoid should also illuminate. Test the other pressure switch and solenoid using the same procedure.




By removing the plastic cap on a pressure switch and turning the setscrew, the turn on point for each pressure switch can be adjusted. Turning the setscrew clockwise increases the pressure at which the solenoid attached will open, and turning the setscrew counter-clockwise will decrease the pressure at which the solenoid will open. The pressure switches are set to a very low-pressure value initially and will have to be adjusted for proper use. A good starting point for the two-nozzle system is 35% of full boost for the first nozzle, and 75% of full boost for the second nozzle. For example, if full boost is 15psi, set the first nozzle to (15psi x.35% = 5.2psi) and the second nozzle to (15 x 75% = 11.2psi). These are just suggested starting points. Adjust the pressure switches by turning the setscrew one complete turn and then testing the system.




  1. Pump never turns on.

Using a voltmeter, connect one lead to the terminal used for the red wire on the pump and the other to the chassis ground terminal used for the pump (black wire). Make sure there is voltage at the red wire connected to the pump when the ignition is turned on. Make sure a good chassis ground is used and the connection to the chassis ground is good. Check the connectors on the pump itself and be sure they are connected correctly.


  1. Solenoids never come on.

Using a voltmeter, connect one lead to the COM connection on the pressure switch. Connect the other lead to the chassis ground used for the solenoids. With the ignition on, and the toggle switch in the on position, be sure there is 12Volts available.


Purging the system


The system can be purged using the following procedure. This can be helpful if the pump runs but is not developing any pressure, or if the car is going to be stored for an extended period of time. This procedure should be done about once per year to ensure that the system is operating at full potential. The accumulator may leak some of the air pressure when in use for more than 1 year and hence may need to be re-pressurized.

  1. Disconnect power to the pump by removing the ground wire.
  2. Drain all the air out of the accumulator by unscrewing the nipple on top of the accumulator. Then push the tire valve in until all the air is released.
  3. Turn the ignition to the on position, and turn the master switch on.
  4. Disconnect the intake plumbing so that water can flow out of the nozzles without going into the engine. If this is not easily done, you can also unscrew the fitting from the accumulator to the solenoids with some method to catch the water, as it will spill out. Skip step 5 is you choose this method.
  5. Using an alligator clip or similar item connect the COM and NO connections on the pressure switches to empty the system. Then disconnect the jumper/clip.
  6. Turn off the ignition.
  7. Drain and refill the reservoir.
  8. Pressurize the accumulator to 50psi using a compressor or tire pump.
  9. Re-connect the ground wire to the pump.
  10. Turn the ignition switch to the on position. The pump should re-pressurize the accumulator and lines to 100psi.


Mounting Screws


Use the 8-32 x 3/8” screws to mount the solenoids. Use the 6-32x3/4” screws to mount the pressure switches. Velcro or other means will also be adequate for the switches. Use the #12 1-1/4” sheet metal screws for the pump, and the smaller #12 ¾” sheet metal screws (left most in diagram below) for the accumulator.

The mounting screws are shown in figure 6. From left to right are the Accumulator, Pump, Solenoid, and Pressure Switch mounting screws. Note to installer: This is the most generic hardware to mount the equipment. For your custom installation, other or different hardware may be required.


Figure 19: Screw Guide – Left to right: Accumulator, Pump, Solenoid, and Pressure Switch Screws

Last Updated on Thursday, 13 January 2011 06:17