Alcohol/Water Injection by eunos93 of www.miataforum.com

The kit operates like this:
The boost switch & map sensor are connected to the same hose the boost gauge is connected to.
The boost switch is normally off, when a certain pressure is reached, it swithes on the current. Which then switches on the relay. The relay & boost switch are made part of the ignition circuit (same circuit that lights up the dash), which only activates when the car is turned on.
The relay, once activated, then switches on the +12V from the battery. That current switches on the solenoid check valve, and the current will flow to either the shurflo pump (only if the controller bypass switch is on) or the +12V lead of the microprocessor controller (for progressive control mode). The map sensor output is fed to the controller.
The controller being used is the Devilsown controller, you can read about it here:
www.alcohol-inection.com
Whether the main current flows straight to the pump or to the controller, is determined by the switches on the control console.

Here are images of the overall layout, and the circuit diagram.
The boost switch connects the circuit at 4 psi (user adjustable), basically activating the controller and opening the solenoid valve to the water/alcohol line. The MAP sensor output to the controller simply regulates the voltage to the pump thereby controlling the injection flow rate.
The controller is akin to a MAP sensor output controlled solid state potentiometer, i.e. higher the boost, higher the voltage to the pump. Parameters are set on the controller, psi at which flow begins, and psi at which the pump reaches full flow (12V).
On this setup, the pump begins injecting around 5 psi, and reaches full flow at 8 psi.

The control console simply houses the switches and the alcohol/water tank low level light. One switch allows bypassing the progressive controller for single (full) flow rate mode. This mode is full flow rate, or off - of course this mode is only used if the controller where ever to fail.
The other switch (spring release) is for manually switching on the pump to full flow rate at any time, for testing purposes. The switches are included simply as a means of fault finding, should one ever occur.

Here is the parts list:

A Devilsown progressive controller, boost switch, microprocessor controller, 150 psi shurflo diaghragm pump, 12V. A simple DIY status panel - made up of only lights and switches. Also a relay harness, 2-bar MAP sensor, solenoid valve, relay, bag containing compression fittings for tubing and brass water nozzle, boost switch (4psi - 15 psi variable).
Note the temporary water bottle shown in this photo. It also contains a filter (nylon pantyhose works wonders) to prevent the nozzle getting clogged.
Later, a much larger container will be used and kept in the trunk, it will contain a float switch that will activate the warning light.
The nearly finished product:
Note the position of the air intake temp sensor, now re-positioned on the air intake pipe, the air intake sensor inside the AFM is currently not being used. All of the spaghetti wiring has been crammed into the black wire loom.

The injection nozzle is screwed into the red air intake pipe, and can just be seen at the bottom left, on the intake pipe just below the radiator hose in the picture (follow the blue water hose down).
Just above the radiator hose is the 12V solenoid valve. This is activated by the boost switch, preventing liquid siphoning into the pipework & intercooler.
Temporary alcohol/water mixture in tank. The black thing is the low level switch, wired into the control console to warn of low alcohol/water level.
This the light which turns on when the tank is half full. You can see where the status panel was finally mounted.
The system is still running great. I’ve been injecting dilute methanol/water mixtures near the intake manifold to give additional fuelling. I decided to go down this route to bigger power as opposed to the more conventional ECU replacement & bigger injectors approach.
So far it is working very well. 0-60, somewhere under 6 sec. The setup I’m running is basically a Greddy turbo kit, intercooler, 2.75” Enthuza turbo exhaust, BOV, Bipes ACU and the DIY alcohol/water injection system. This is a progressive control set up, meaning that as boost increases the rate of injection increases too.