Holy crap, some genius has just figured out how to save the world with 100mpg fuel economy and, in one fell swoop, broke the laws of physics, chemistry, and thermo-dynamics, again. A couple weeks ago, one of my friends over at Motor Trend sent me a link to some new fangled bolt-on fuel saver kit promising to make just about any car on the road today crank out a fuel economy numbers just shy of cold fusion. I'm not sure if he sent it as a joke, or was really curious, but this I had to see. Maybe I could even install it after my Tornado and electric turbocharger came in the mail.
So, after sitting through the first of two 30-minute clips at www.preignitioncc.com/default/flashHafcHi.htm, that looked a lot like the Hale-Bopp worshiping Heaven's Gate cult videos, I was ready to kill myself. Curiosity really does kill the monkey. The idea that this company can double your fuel economy with a ragtag accumulation of random hardware, called their Hydro Assist Fuel Cell (HAFC), had me incensed. Even worse was the idea that some poor soccer mom in the armpit of New Jersey would, and probably already had, fallen for this.
The company starts off by introducing their fuel-saving solution, which comes as two kits, the Hydro Assist Fuel Cell and the Pre-Ignition Catalytic Converter (PICC), which hasn't been released yet. It takes them 10 minutes to establish this point. So, you find out that the HAFC is basically made of four totally non-related components; a so called fuel cell (that's basically a stainless tank with electrodes wired to your battery to allow your car to run on water gas), a fuel heater/ionizer duct taped to your radiator hose, some covalizer fuel additive and, of course, the magic black box they name the Optimizer that intercepts the signal coming from your O2 sensor and tricks your ECU into giving you the fuel economy that the OEM's have conspired with the government to deny you. These people were hitting the comet dust way too hard. I tried to forget about the matter.
The water gas topic reared its ugly head again when a good friend approached me about making his car run on water gas, or brown gas, because of all the forum buzz on the topic. Even after explaining to him why the process doesn't work, he was still willing to try it anyway. Desperation can make you do stupid things. So, I'll break down the concept of water for fuel for all you imaginative fuel savers.
The internal combustion engine is an air pump. In order for the engine to do work, ambient air has to be compressed and then expanded. Fuel is used in the expansion process and it's the energy stored in the fuel's chemical bonds that the engine's power comes from. Fuel is essentially a battery, or a means of storing chemical energy and taking it with us where we go. We use petroleum-based fuels, since it stores a lot of useable energy, is easily transported, and takes relatively little energy to process to a useable state. As of now, it's the best bang for the buck for energy available on a large scale.
Petroleum based fuels are made up of long hydrocarbon chains where hydrogen atoms are bonded to carbon atoms. It's the energy stored in these relatively weak hydrogen bonds (H-bonds) that power your engine. The weakness of these H-bonds is also why fuels are so volatile and unstable. By sparking the air/fuel charge, you catalyze an oxidation reaction, also known as fire, that breaks the H-bonds releasing energy.
You can use anything that stores chemical energy as a fuel. The H-bonds found in organic molecules in wood can also work as a fuel, but it's just harder to light and stuff into your gas tank. That's why we prefer gaseous, or liquid fuels, which fit better in some sort of gas tank.
Here's where the concept of water for fuel and water gas comes in. Water gas, (which the scientific community would actually identify with water vapor or steam, instead of the gaseous components of water), aka brown gas, Brown's gas, or more appropriately oxyhydrogen, is actually a mixture with a ratio of two hydrogen molecules for every one oxygen molecule. It comes from breaking water down through electrolysis into its basic components, (2H20=> 2H2 + O2.) Calling it H-H-O is also a misnomer as oxyhydrogen isn't some strange molecular rearrange of the water molecule H-O-H. H-H-O as a molecule can't exist in stable form just because of its electron arrangement. Calling it by what it actually is, H2+H2+O2 might help.
Regardless, instead of using the H-bonds in hydrocarbon chains, you can use the same H-bonds holding the hydrogen molecules together in Brown's gas as fuel. Hydrogen, like many gases in a stable natural state, exist as a diatomic molecule with two atoms double bonded to each other in a pair like hydrogen (H=H) and oxygen (O=O). The two atoms are now held together with two H-bonds making the molecule slightly harder to break apart and combust. Hydrogen can be used as an alternative fuel just like ethanol, CNG, or LPG. Just throw some oxygen at it and you're ready to rock the Hindenberg. You also need less than half as much weight in H2 than you would if you were using gasoline (since its stoichimetric air fuel ratio is 33.43:1 compared to gasoline's 14.7:1). The tradeoff is much higher combustion temperatures, which will decrease your knock threshold, increased wear on your engine and more NOx emissions (that's the brown stuff in the air) than gasoline.
Using hydrogen as a fuel isn't really the issue, people have been doing it in various applications for years, but how you get your hydrogen is. This presents the primary dilemma with water for fuel. In order to get the hydrogen gas from water, you have to spend electrical energy from your battery to break water down into its parts, a process called electrolysis. In a laboratory experiment, that's fine and dandy since no one cares about how much electricity it consumes. But, in a car, where the power for your batteries comes from your alternator (which is driven by your engine), it doesn't work. Broken down, water for fuel uses the energy that's in your fuel to both power the car and to create more fuel.
That's fine if you get more energy out of hydrogen gas as a fuel than it takes to make it from water, but that isn't the case. H2O is the lower energy state for two parts hydrogen and one part oxygen. Not the pure gas forms. That's why water is so abundant and we harvest hydrogen from water, not water from hydrogen and oxygen. A real fuel cell, which does work, runs the opposite direction by extracting the electrical energy of combining oxygen and hydrogen into water. The energy cost of making the hydrogen gas for fuel cells isn't as severe since it's done at a stationary processing plant. In reality, the practical electrolysis process is only 30-45 percent efficient, not to mention the irreversible losses you incur (called heat) every step it takes to get from combustion to electrode potential. Bottom line is you're losing your ass on this energy balance.
Just to rain on the water for fuel parade even more, no one's considered the rate of reaction or the volumes involved. If you were to run your 2L engine on hydrogen fuel only, just at idle with a stoichimetric air-fuel ratio of 34.33:1, you would be consuming 78.5-liters of hydrogen gas per minute. (We're ignoring the effects of the oxygen also generated in the process since hydrogen is the limiting reactant.) Just to supply that much H2 gas means you have to turn 63cc of water into gas every minute to just to keep the engine running (don't ask how many people I had to consult with before remembering enough chemistry to figure this out). You'll notice two things. You need a lot more water to run your car than most cars will carry, and you need an obscene rate of electrolysis. If you've ever seen electrolysis off of a 12V battery, it happens one bubble at a time.
Proponents of using water gas will say the concept should only be used as a dual fuel process to boost the fuel economy of a conventional gasoline engine. Even so, the energy balance is still not in your favor. You're wasting more energy from the gasoline just to get a small amount of hydrogen and oxygen.
Now the point of this isn't to make fun of or bash on what other over imaginative people are doing without giving them a chance to defend themselves. At least I'm trying my best not to. Crazy people are usually the ones that create world changing inventions and make it into the history books. Crazy people are also the ones you don't want to piss off. I'm just pointing out the physical limitations of the process under current accepted theory, which they are welcome to try to disprove.
I applaud the efforts of what people are trying to do to save gas. This is what progress is about. Ever since the invention of the engine, which converts chemical energy into mechanical energy there's been someone else that's tried to make something better and more efficient. Some work and even fewer have made it into the engineering books as something more than just a historical side note. The difference being, the ones that work, work on paper and in application. The ones that don't are just hair-brained ideas that some homebound inventor came up with and tested erroneously without even considering thermo-chemical or physical law. These usually end up on some patent clerk's desk, wasting time, collecting dust, and ensuring the clerk's job security.