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Rene Mapua's Water Injection Report

H2O Injection Installation and Test
April 7, 1998

Finally I have the long awaited personal evaluation of the H2O injection. Note that this is the Aquamist System 1 made by E.R.L. of England. For an excellent look at exactly what the kit contains go to http://www.aquamist.co.uk/cp/sys1/sys1a.html.

A few confessions first. I am not really good at computers. This is my first ever attempt at any sort of document publication. Someone should edit this so that I don't confuse too many guys with that regard. I have only a very close relationship with a terrific friend who is a very serious competitor on the racetrack and most, if not all, my technical and racing knowledge is because of Mr. Jojo Silverio. I must say that, after my old friend Jovie Marcelo, the Filipino that died in Indy a few years back, Jojo is the most successful Filipino racer there is today. He got me started by racing go-karts. We won lots of rallies and national championships together when I navigated for him from 1989 to 1991. Last year we both drove factory backed Mazda 323's at the Subic raceway where the old U.S. navy base used to be in Olongapo city here in the Philippines. He was in the "A" class and I was in the "B" class. He won the championship against factory Nissans, Toyotas, Hyundais, and etceteras in what would probably be called your showroom stock class (with a few more modifications allowed). I finished 3rd in my class. I could have won but I missed 3 races due to illness. Darn.

I first learned about H2O injection from the Messerschmitt Bf-109, Germany's WW2 fighter in the Battle of Britain. (I am serious radio control model builder and pilot when I am not behind the steering wheel or desk.) I then thought why not try it on the miata? And I looked, behold, a kit!

There is one slight catch. The spray nozzle is supposed to be located upstream of the throttle body's butterfly. For example, as in the Greddy turbo installation, this makes the use of a solenoid switch unnecessary. It then becomes mandatory for us guys using the Sebring supercharger. Because during "unboosted" engine operation the H2O still trickles into the intake manifold as there is no butterfly valve to cut off the intake manifold vacuum pressure. This causes the engine to idle somewhat erratically. I improvised a lot, maybe too much, and things may have become redundant in solving this problem. You guys let me know if there is a simpler and neater solution.

The only machine shop work that needs to be done is to the dummy throttle body. Wonderful in the sense that we don't have much to dismantle. Aquamist says to put the injector at a 45-degree angle facing down and into the intake manifold. I had to (Is the term "chamfer"?) chamfer a seat for the O-ring of the spray nozzle then drill and tap.

Also drill and tap for the adjustable pressure switch. There is a tap that comes with the kit for this and a self-addressed envelope for its return to Aquamist so that others may use it. Just follow the directions from the kit and everything will go well.

Yes, I know this looks and sounds like an electricians nightmare but it's really not that hard to do and if a dummy like me can do it, anyone can and will probably do a better job.

The reason for the need of this magnetic switch is that there exists a current in the variable pressure switch, which the solenoid senses. I needed still another cut-off for that. I put it inside the fuse box where there happens to be a cavity where it sits very nicely.

Once this puzzle was solved. Everything went very well. My test tank was the windshield washer tank and I just flushed out the tank to remove any detergents and stuck in the hose. I now have an old go-kart fuel tank, which holds about 8 liters (about 2 gallons), and a longer hose located in the trunk. There is no problem with hose length from tank to the H2O pump that I have experienced. Water spray is always instantaneous on demand from the pressure switch.

What follows are the results of all this work. At last. With everything buttoned down and idiot proof we went to the track.

With absolutely no other changes to the set-up of my miata except for advancing the ignition timing to 12 degrees and of course the H2O injection, off we went.

I tried to induce detonation. I finally got some when I went from 1st gear straight to 5th at about 1,500rpm doing about 30kph and mashed the gas pedal to the floor while the air conditioner was on full. You had to really listen for it because it was barely audible. It happened at around 3000rpm and was gone at around 3,300rpm. When I tried to advance the timing 14 degrees, detonation was again audible all over the rpm spectrum but still not as bad as without the H2O injection at, say 6 degrees advance. I then set the timing back to 12 and all was fine. I can now mash the throttle pedal to the floor anytime. No need to be gentle. Throttle response is much better and the engine feels really light and easy. Getting to the rev limiter happens much quicker. The rpms climb through the tach so much better that I took away a whole 3 seconds of my best lap time before H2O injection. Not to mention that this was done on a hot tropical day at noon with the air conditioner on.

Now I have another question for you guys. How do the guys that race their miatas over there in the U.S. deal with the overheating problem? Over here, even the bone stock miatas overheat after a few laps. This is now the major deterrent against starting an all miata class for racing here in the Philippines. If anyone can tell me how he or she does it, I'll really appreciate it.

All in all I'd say the effort was well worth the reward. I have absolutely no idea what the long-term results will be but at least I am no longer audibly detonating.

When is that 9psi pulley and air to water intercooler going to be ready? I'm ready. I wonder what happens at say 50% methanol and 50% H2O mixed into the water injection system. This I want to try also.

If you guys want to ask me about what I've done please don't hesitate to email. I'll try my best to answer everyone as best as I can.

Rene C. Mapua
"Wet and Red" 96
Supercharged with H2O Injection
Manila, Philippines
Rene C. Mapua
"Wet and Red" 96
Supercharged/Water injection
Manila, Philippines

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Last Modified: April 10, 1998
Copyright (C) 1998, Kory Hamzeh. All Rights Reserved.