some ideas about the physics of the hydro-assist technology, and implications

A friend just asked for my opinion of the "hydro-assist fuel cell" modification. I don't know whether or not it works, but if it does work, there are limited ways in which it could, and these appear to me to be potentially problematic. I haven't searched the CR4 site to see if this has already been dealt with --- one thread that I did find was shut down in April and was inconclusive, as far as I could tell on a quick survey. If this matter has been carefully dealt with somewhere on the site, pardon my waste of your time as you already know this. This is an anonymous post and I won't be checking back in.

I think my friend would have been unwise to install this product on his car, and similar modifications or do-it-yourself mods may likewise be problematic. These are the reasons:

The modification appears to use engine-generated electricity to split water into hydrogen and oxygen. These are then added to the fuel/air mixture and burned in the combustion cycle.

The additional mechanical energy produced by the burning of the hydrogen must, by thermodynamics, be no more than the electrical energy used to split the water. Since this electrical energy is supplied by the engine (battery/alternator), this by itself cannot improve the engine's efficiency. If there is improvement in engine efficiency, it must come from somewhere else. The only place that I can think of is a possible modification of the dynamics of the combustion cycle.

The H/O vapor mixture produced by this mod is more combustible than the gasoline droplets of the fuel/air mixture, so this modification ought to result in a hotter initial explosion after the spark. A hotter initial burn might lead to more rapid combustion of the fuel/air mixture and this would result in higher temperature and pressure in the cylinders at the early stages of the combustion stroke. That would lead to more efficient burning, which I believe would improve gas mileage. This is the principle on which the well-known Pogue carburetor works. So it appears to me that Hydro-Assist works in a way that is similar to the physics underlying the improved efficiency that Pogue carburetors have been reported to give.

However, there is a cost to this improvement. Car engines are designed for the standard combustion cycle which has a slower, cooler burn with lower pressures at the beginning of the combustion cycle. To modify the engine to have higher pressures at the start of the combustion cycle could result in a combustion cycle that exceeds the pressures the engine is designed to sustain. I don't know enough about engines to foresee all the possible failure modes, but here are few that come to mind:

* head gasket blowout. The head gasket is a seal between the cylinder head and the main body of the engine block. Higher pressures at the outset of the combustion cycle might gradually force this gasket out of place, resulting in burning fuel/air mixture escaping into the engine compartment. That is not good. At the least, it would require a not-cheap repair. At worst, there might be an engine compartment fire and the need for very costly repairs.

* Bearing failure. The bearings between the piston rods and the pistons and between the piston rods and the crankshaft are designed for the kinds of stresses that occur during the normal slow burn combustion cycle. A fast burn, higher pressure combustion cycle might subject these bearings to excessive stresses that would shorten their life, resulting in sooner need for costly engine rebuild, or even perhaps a catastrophic bearing failure and a possible engine write-off.

So I believe that this modification might very well improve mileage. But before installing it in a vehicle that I hoped to get many miles out of, I would first want to know what the effects of this modification would be on engine wear and lifetime. My belief is that it would shorten the engine life. It appears to me that there are numerous claims of improved engine mileage. In my quick internet survey, I have not seen discussion about what the implications of this modification are for engine life