Miata Turbo Forum - Boost cars, acquire cats. - Home Brewed Water/Methanol Injection System

I designed and installed my water/meth injection. I didn’t buy a kit I pieced it together from purchased parts and parts I had laying around already. I don’t think it saved me that much money vs buying a kit but I think the end result is really good and I learned from the exercise and got satisfaction from doing it myself.
It’s a two stage system, i.e. 2 boost pressure switches acting on 2 solenoids. I have 3 fluid pressure switches feeding 2 LEDs in the cockpit for system indications. One NO switch just downstream of the pump and one each NC switches just downstream of each solenoid. When the system is pressurized both LEDs illuminate. Then as each of the solenoids open the respective LED goes out. I like this because it gives me system pressurized indication and then positive indication of pressure going to the nozzle not just an indication that there’s power going to the solenoid. I used the coolant overflow bottle as my reservoir, I use a different bottle as my coolant overflow. I also installed a float switch in the reservoir so I have low fluid level indication via an indicator lamp. I have a push to test switch so I can test to check the low level lamp is working. The first stage starts injecting at 6 psi boost, the second at 12 psi. The nozzles are both 1 GPH.

I also have an air/water intercooler. My system is currently running about 13 to 14 psi max boost.
I found that once I increased my boost above 10 psi the air/water intercooler wasn’t cutting it. I had to adjust the timing (PCPRO timing card) significantly to prevent pinging and on hot days I was seeing quite a bit of activity on my knock gauge.
After I added the water/meth injection I was able to back out most of the timing adjustment. The power band is much smoother now that it was before and it feels like I have picked up some power gains.

I haven’t dynoed the car (I plan to at some point in the near future) but it runs great.

This text and photos at miatabuildthread.blogspot.com