I have been meaning to install a water injection system on my supercharged MX5 for some time.

The car had to go through massive surgery since the "accident" back in December, so all plans had to be put on hold for a while. All I could do was order and gather parts and pieces during the almost five month period.

Anyway..

I would like to thank Joe Perez and ZX-Tex for giving me ideas and help to get this whole project off the ground.

I wanted the whole thing as much out of sight as possible. There is minimal trunk space to begin with, and any sort of a reservoir in there would make the trunk pretty much useless.

So, I developed a few ideas:

One was to make custom water tanks to fit in the rear wheel wells. Besides a plumbing nightmare that would create (balance lines between tanks, for instance) the available volume was really not worth the hassle once I put the car on a lift and examined the openings around the wheel wells.
Scratch that idea..

The second one was removing the spare, and making a custom water tank to fit in the spare tire well. That would hold plenty water.
So, I proceeded to plaster cast the whole area to make a mold for vacuforming.
But there was again a volume issue.. Too much water. Too much weight. Little room for the pump, etc, and one little warning about the pump having to be below the water tank level.
Scratch that idea, too.. And the massive plaster cast became a part of the landfill:

 

I am having trouble seeing the pictures. Where are you putting them?

 

So, the third idea was to build water tanks to fit in the openings on either side of the gas tank in the trunk..
The left side opening is visible in the pic:


Turns out, two tanks in these openings carry about 10 liters (about 2 1/2 Gal), which is plenty.
My main concern was running out of water on the freeway.

 

I proceeded to make the water tanks..

I searched for what I could use, and settled on 1 mm thick clear pvc.
Here is the prototype: (Those measurements are not in inches.. Also, 14.5 cm was a much better fit than 15 for the width.)

 

I first drew and cut out the basic shape on the pvc, and then used CA glue and some seriously tough water resistant silicone (Bison PolyMax) to glue the edges.

 

 

I made a bending/folding tool using 3/4" mdf and a piano hinge.

I cut two 60X10 Cm and one 60X15 Cm piece of mdf boards, and joined them very carefully with the piano hinge.

Worked great with the help of the heat gun..

 

I also bought an AEM 30-3001 5 Gal. progressive water injection kit.
(5 Gal kits come with a larger, beefier pump)

The idea was to use the level sender out of the kit's reservoir.

I also bought various plumbing fittings and pneumatic fittings to route the water lines..

(Excuse the silicone mess, that stuff gets trimmed once it dries..)

 

I also wanted to make a cool filler..

So, I used the only logical spot for that, and fabbed a filler neck, complete with an air vent to prevent air lock in the water tanks.

 

 

The air bleed/vent is a 30 micron mesh filter. No dust or dirt could get in..

 

Pics are showing up now. And, WOW this is serious!

 

I wanted to use the AEM kit to a certain extent..
What I really want is a direct port injection system.

So, I made some calculations, and ordered four 70cc nozzles, and "T" connections from Aquastealth.

 

 

Aaand, promptly bıuilt a test stand to test the nozzles..

The results speak for themselves..

 

 

Here is the test stand:

 

(Yes, that's my teacup on top of the water tank. Takes about half a quart..)

 

And clearly this is an understatement.

 

I used some pretty large fittings for the fill tube just to increase the available volume, just like the old NASCAR trick:



I could not find washers for those tank fittings, so I made them out of a PVC down pipe (the kind used for rain gutters)