INSTRUCTIONS: Page 1 2 3 4

Trigger Device and Controller

Labonte Motorsports water injection controller

Manual or automatic? You can flip a switch to turn on the pump or it can be handled by a sensor. It all depends on how much you want to spend. There are several injection sites that manufacture control boxes. Personally I think that a control box is well worth the money. It will allow you to have more control over when and how much fluid those nozzles will spray.

Pump Controllers:
There are many to choose from. Do your homework and decide which one works best for you.

This site has “Snow Performance” style controllers. Until October 2007, all Labonte MotorSports products have been marketed through Snow Performance. You can now purchase them through the original manufacturer. They also have a controller designed for carbureted engines.
Snow performance does not have a page to purchase a controller separately.


By varying the voltage to the pump you are able to control the water pressure and amount of water going into the intake. This is accomplished by using a controller. I used one by Snow Performance. Like most controllers it requires input from a sensor to control the voltage going to the pump. Lower voltage = less pressure & water.

The Input that this unit was designed for was from the MAF sensor.  The voltage output from the MAF is from 0-5v. That voltage is translated to a 0-12v output to the pump. You can set the start and full pressure settings by adjustable dials.

Most sensors send voltage output to the computer in a 1-5v range. For example, at idle the MAF output is 1v. You set the first dial on the controller to start the pump at 3v so that it is not pumping water at idle. The next dial setting is for when you want the full 12v to go to the pump. Set that at 5v when the engine is at full throttle. Everything in between is a smooth linear increase from no spray to full spray.


Labonte Motorsports Injection Controller for Fuel Injected
Engines w/ MAF

Voltage Regulator

I used a voltage regulator as my sensor input because my MAF has frequency as output and not voltage. This voltage regulator uses a rheostat to vary the voltage. Think of it as a volume knob attached to the throttle. For those of you who have carburetors, this is the only way you will be able to get this system to work unless you get one that uses vacuum (see Labonte MotorSports).


Voltage regulator modified

I modified the voltage regulator by removing all of the capacitors because when the throttle was closed there was still voltage bleeding off. I also added a resistor to the incoming voltage to reduce it from the 14.4v of a running engine to approximately 7 volts. This gave the controller the near value of 0-5v it is looking for.

You could also just use a 30amp DC Motor Speed Controller and forget about all the other controllers. Attach the rheostat to the throttle and that will control the voltage to the pump. Measure the output voltage at idle and full throttle. Idle should be 0v and full should be no more than12v.

Modified regulator in a plastic hobby box from Radio Shack



rheostat throttle bracket mount front view The rheostat has machined groves in it to fit on standard control knob found at any Radio Shack. I used JB Weld to attach it to the throttle body.
rheostat lever switch throttle bracket mount side view The rheostat is attached to a floating mount on a bracket. I had to use this method because getting the knob centered exactly on to the throttle was almost impossible without removing it. The spring and allen bolt allow the mount to move on the bracket to prevent binding and make up for the misalignment.
lever switch close up side view Here you can see the lever switch resting on a part of the throttle. When you step on the gas the switch will activate the relay which will open the main injector solenoid and close the pressure relief solenoid. When you step off the gas, the main injector solenoid closes and the pressure relief solenoid will open. As I said before, the reason I had to install a pressure relief system was because I was still getting water spraying after the solenoid closed. This is due to the high pressure in the lines and the low flow rating of the nozzles. Being that this is a NA engine, low flow rates on water is necessary.
Water Injection solenoids

Here is the layout of the injection solenoids. Water comes from the filter into the left side of a 4 way distribution fitting (3 out from the bottom and 1 out from the right). The right side goes to the first solenoid which is the main injector. One of the bottom exits is plugged off. Of the other two, one goes to the rpm solenoid and the other goes to the pressure relief (overflow) solenoid.

The main injector solenoid and the pressure relief solenoid are controlled by the same relay. Either one or the other solenoid is active. You can check the main wiring diagram to see how they are hooked up. Because all of the solenoids come from the same distribution fitting, the pressure is relieved from all the lines when the Pressure Relief Solenoid opens.

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