What is it and why do I want it? Wikipedia has good answers HERE.

Update  water/methanol mix with smaller jets, and the addition on a vacuum gage have proven to be the best (and cheapest) improvements for better MPG.

I started this because the hydrogen generator caused ping (I expected that) and retarding the ignition did not seem like something I wanted to do, because it made the vacuum drop (which means the carburetor is putting more fuel in).

This is a cheap plastic aquarium valve. I had a piece of aluminum tube that was a perfect fit for one hole. This will be the water pickup tube and extends to the bottom of the jar.

The amount of water entering the engine is adjusted with the needle valve by watching the rate at which bubbles enter the jar. I set it initially at one bubble per second at idle. The other end is a lawn irrigation 90° fitting inserted into a hole in the PCV hose going to the manifold. This is how it draws a vacuum to suck water from the jar.

The first surprise was all the black crap it blew out the exhaust. I had thought it was pretty clean after running hydrogen. This (and white smoke) stopped in a few minutes.

I drove to the store 5  miles away, stopped and opened the hood. NO bubbles. So far I have had to open the valve twice. I suspect the plastic needle changes with temperature. It this persists, it will be replaced with a brass valve with stainless needle.

According to the National Weather Service, the relative humidity is 3% !

The car runs smoothly and has enough power the spin the rear wheels. At 45 miles an hour the vacuum gage reads 15-16 inches. It may take a while for me to get all these things optimized, but so far I am very pleased.

A word of caution if you would like to try this yourself... The jar must be well sealed in order to use the number of bubbles as an indicator of how much water is being injected.

April 18, 08
I am making a new jar that is glass with a metal lid and replacing the plastic needle valve with a brass one. Not much to it really. The new one will connect to the venturi vacuum port on the carburetor instead of the PCV port. Why? While the PCV connection seemed to work just fine, I feel the vacuum port will allow for better mixing.


April 19, 08
The brass needle valve was a big improvement over the plastic aquarium model. Upon starting the engine there was no black soot ejected from the tail pipe as there was the first time. Maybe that means it got cleaned out.

I checked the bubble rate after 5 miles. No change. Checked again after another 5 miles. No flow. This won't do. For the 18 mile trip the water level dropped about 3/4".

Oh, yes... the new jar is glass that 24 ounces of yucky cheese dip came in. It has a metal lid and sort of a rubber seal. I attached two 90° barbed irrigation fittings with J-B Weld from both sides. 

Back at the shop I tried an irrigation drip system flow metering emitter on a hunch. It is rated at 1 gallon per hour. Somewhere around here I have some that are 1/2 gallon per hour. Even that sounds like a lot, but in the jar the bubbles are coming at about twice what I am going for with the 1 gallon emitter, so the 1/2 gallon one should be about what I want.

This is what Irrigation Tutorials says about this type:

"Diaphragm" emitters all use some type of flexible diaphragm to reduce the flow and pressure. There are many ways used to do this. The bottom line is they all use some type of flexible part that moves to restrict the water flow. As with anything that moves, they will wear out eventually (which may be a very long time!) which is the downside. The advantage is that they tend to be much more accurate in controlling the flow and pressure than the previous types.

If you intend to try this device, be aware that the pointed barb should go toward the supply jar.
This looks like a much better idea than an orifice or a needle valve. Next will be to try various injection mixtures that other people have used successfully. http://www.waterinjection.info/ Windshield washer fluid seems popular.

It is funny that I started the HHO generator and the water vapor injector projects with first class hardware, then ended up replacing most of it with lawn irrigation parts that were MUCH cheaper and easier to work with.

I bought a bag of 25 emitters rated at 1/2 GPH. I thought maybe I should start the engine then plug them in. Then thought "Naw, it will be ok.". Every one of them is defective (made by Raindrip). No diaphragms. The engine sucked in about a pint of water before I could shut it off. Does not seem to have done any damage, but very scary nonetheless. I used a 1 GPH emitter that seems slower than the rest. Time for some serious mileage checking.

I have found these offered in flow rates of 2, 1, and 1/2 GPH, plus 4, and 2 (.6GPH)  Liters/minute. I dissected one of these and found the diaphragm is much thicker than I expected and has sort of a zig-zag maze on both sides of the disc. Clever design.


I added denatured alcohol to make a 40% mixture. When I started the engine I found a fresh batch of carbon soot on the concrete behind the car. Guess the alcohol helps clean it even more than just plain water.

April 22, 08
A new set of jets were made by soldering the holes then re-drilling to a diameter calculated to have 20% less area than the original jets. This is NOT recommended by Holley, because you are not real sure what the exact flow is. For instance, a #65 jet has a flow rate of 65 CC/min. I am fairly confident though, since I have been doing this since the 1960's. Do it at your own risk! When I think I have the size I want I can order a broached set that has been flowed.

The plan is to check my theory that a much leaner mixture will not seem lean to the engine because the hydrogen enables more effective burning of the gasoline. The water and/or water/alcohol injection should help prevent preignition.

This sort of experiment is not for the faint of heart because serious damage can be done to the engine if you are not careful. Also, these modifications mean that I can never let the hydrogen cells or the water injector run out of water.

April 25, 08
Last night I tied epoxying a short 1/16 brass tube in the end of a dripper, then used pliers to pinch the end almost closed. Not a very elegant solution to reducing the flow when using an alcohol mix, but it worked. Idle was smooth and when the solution reached the carburetor the idle and vacuum increased. The dripper reduces the pressure, the brass tube reduces the flow.

I marked off ounces on the side of an olive jar (because it is tall and thin to give a slightly more accurate reading). 4 ounces of Walmart windshield washer fluid ($1.48/gallon) was added and I timed how long it took to drop the level an appreciable amount, then measured and calculated the following:
    .516 ounces/minute
    $.0059/minute
    248 minutes per gallon
    $.35 per hour
Turning the hydrogen on increased the idle speed, and the water/alcohol mix increased it even more. At least this makes it look like I am on the right track, and I can live with the cost of the washer fluid at the above rates.

Road testing. The car ran very smoothly with lots of power. I am wondering if that means I can lean it out a little more, but I want an idea of the mileage before I can think about that.

After 10 miles, the level in the jar dropped by 8 ounces. Most of that was at 45 miles and hour, but there were several traffic lights and stop signs.

April 28, 08
The jets are even smaller now, #55 drill size or  .055" diameter, which is 31% smaller area than the original jets. There is a little reduction in mid throttle power, but open throttle remains unchanged as far as I can see. This is because the power valve opens at 5 inches of mercury. One size smaller than that was tried first with major reduction in performance.

I can see little difference with the the hydrogen on, or off. That is a disappointment. Other people claim great gains with hydrogen, but it varies greatly from car to car.

May 4, 08

One gallon jug in place of windshield washer reservoir.

I finally have some real figures on mileage. Previously the best I could get in mostly town driving was 10 MPG. Sometimes that went as low as 8 in the winter.

With the HHO off, and the leaner jets and water/methanol injection I got 12.94 MPG. Much of the time the air conditioner was on, and I made a few performance runs that really suck up the gas. Not all of the time did it have the really small jets, just the ones I purchased that were 9% less flow.

Average cost of water/methanol, city driving, 7 cents / gallon of gas used.

For this test with lots of stop and go miles the saving per gallon on gas is $.994 (actual measurements) 

This is very encouraging for a 5600 pound car with a 7.5 liter engine. 

My previous MPG highway was 15.4. Hope to get it up to 20 MPG.


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