H2N-GEN Car Gadget

This is an interesting gadget that has popped up on alot of radars. Just read about it in this month's popular science edition and have seen several web links other than the engadget review. In short this is a rather odd gar gadget claim. The basic idea is that the gizmo takes electricity and splits some distilled water via electrolysis and the resulting gasses (hydrogen and oxygen) are pumped into the intake and added to the regular combustion process. At that point the inventor claims 10-40% increase in fuel efficiency.

I have seen a lot of people saying that this thing can't work for a number of very good reasons but I am not so sure they are right. So lets deal with them.

First the article lists an increase from 35% engine efficiency to 97%. It is widely known that internal combustion engines are around 35% efficient. What most people don't understand is that this is not due to combustion efficiency. IE the fuel is completely burned. Modern fuel injection and spark systems attain the practical maximum efficiency of burning fuel. The loss of efficiency is in the loss of heat and internal workings of the engine... IE conversion of power to rotational energy and radiating lots and lots and lots of heat. In otherwords the car liberates virtualy all of the energy in the gas, something like 95% in a modern fuel injected engine. However, it only manages to harness 35% of it. This means that there is deffinate room for improovement but if it is realized then you have to be wasting less of the energy that is released in the process of combustion. In other words, you have to be losing less energy as heat. So any increase in fuel efficiency that is not an over unity scam has to result in less waste heat.

Now the idea that burning the hydrogen would add net power is ludicrous. But if you pause for a moment and consider the use of nitrous or water injection in combustion engines then it is possible to see how this might actually work. Injecting relatively small amounts of nitrous or water into the combustion cycle can net 100-300% increases in engine power output from the same amount of burned fuel. Using hydrogen in the same manner could allow you to net your fuel efficiency gain. IE essentially your taking the energy of the hydrogen to create higher compression ratios in the combustion cycle of the engine. When you do this to gain extremely high power for brief periods of time it is fairly destructive to the engine. IE it isn't designed for the increased power. However if you used this ability to create normal levels of power from less fuel then you could realize the claims of the inventor.

You could do the same thing via higher compressions with the pistons, however you hit a problem with detonation after about 10:1 and to realize higher compression ratio's you have to use much higher octane fuels. The added cost of the fuel normally negates any gains beyond ratios of 9 or 10:1. Injecting nitrous or water gets around this problem as this is alternative way of retarding detonation than by directly increasing the octane of the fuel. They are not viable as long term power generation because with nitrous you just shift you fuel costs.. IE the gas is used more efficiently but you only get it by expending nitrous which isn't cheap. Water injection has issues with durability of the engine if memory serves. So my guess is this process works in a similar fashion. Any power derived from combusting hydrogen derived from electrolysis from electricity generated by the engine being used has to be a power losing process. But if that power is used to create higher compression similar to nitrous or water injection than it can serve as a lever to getting more out of the gasoline combustion process and we already established there is more available there and that injection process can be used to get at it.

So here is the basic idea. Lets say the hydrogen generation process eats up 5hp of energy. According to those pesky laws of thermodynamics any direct combustion derived from that process could not net more than 5hp worth of energy. Practical conversion efficiency maxes out in the 90% range. Lets say you can net 4hp of combustion energy from 5hp of electrolysis. If that the re-introduction of that 4hp via hydrogen and oxygen to the combustion cycle serves the same purpose as nitrous or water injection systems then the result would be a 100-300% increase in the engine power output from burning gasoline. IE you are creating a more efficient converstion of the combustion of the gasoline into mechanical power by upping compression not adding power via hydrogen combustion. The combustion is used to up the compression ratio of the engine which in turn leads to higher efficiency in turning the combustion of gas into mechanical energy.

Now also acording to those laws of thermodynamics you cannot get more power out of your gas than it contains. Currently engines get about 35% of the stored energy in gas turned into mechanical energy turning the wheels. The rest is lost in conversion from one form of the energy to another. Most of the drive train is in the high efficiency conversion range... like 90%+ and the real energy loss in gas engines turns out to be heat. So if you are now getting 70% of that energy turned into mechanical energy you have to be either more efficient in the drive train or losing less heat. The drive train hasn't changed so to net 100% increase (35% upped to 70%) you would have to have a corresponding drop in the running tempreture of the engine as it would be losing less energy by radiating it off as heat.

So if this guy isn't a crank then the process would be something like this. You take a 100hp engine that gets say 10mpg at max output. You install this system and immediately you take a 5hp hit. You use the 5hp to generate hydrogen turning this into a 95hp engine getting worse fuel economy if you don't use the result of that process. However IF the hydrogen/oxygen from the electrolysis injected into the combustion cycle has a similar effect to adding nitrous leading to a ~100% increase in power output due to higher compression rates then 95 available hp turns into 190 available hp. You then cut the fuel injected into the cycle in half so now your getting 95hp burning 50% of what generated 100hp before. So at a perfect converstion ratio you are now about 44% more effiecient at turning gas into mechanical energy which is possible. Now instead of 10mpg you would be getting around 14mpg which is at the higher end of his claims. If this is what is happening then the waste heat being radiated would have to decrease by a similar amount so the engine would run cooler. According the the original artical exhaust temps were drasticly reduced. If this is true then the guy may be on to something.

Some may wonder why they don't just do this via nitrous or water injection. The problem is that your fuel costs don't go down with nitrous as you have to replace it like you do gas and it isn't cheap. Water injection to increase efficiency has been tried many times and failed for many practical reasons... namely added complexity. High temperature water is very very corrosive. While this process would still generate some water (hydrogen combustion forms water) you would be forming less. IE this system would up combustion by the result of combusting hydrogen in oxygen... water injection does it by injecting enough water to up the compression due to the fact that water does not compress. If the amounts are similar then this system will encounter similar durability issues when this is used for long durations rather than for short term power boosts.