Good find Steve
The octane rating of H is around 130.
This means that the chances of it igniting from the heat of compression are MUCH lower than with Gasolene.
Increasing the compression ratio of the engine dramatically, or higher turbo boost, will be possible.
This will improve the efficiency of a hydrogen engine, or partial H engine, a lot!
(Increasing compression will allow the use of less H; something that has not been tried or tested in this type of community)
The energy required to ignite H is dramatically lower than that of gasolene however:
This means that any hot spots that were not issues in a gasolene engine may well become issues in a H (or partial H) engine.
Extra care will be needed to round off any sharp edges in the compustion chamber.
This goes hand in hand with the quench distance described in your document, that keeps metal surfaces from melting.
The quench distance of H is about 40% that of gasolene: 0.5mm as opposed to 1.2mm approximately.
This will increase the chances of hot spots dramatically.
It will also cause more heat to make it into the sleeve and head etc, which means that a bigger radiator might be required.
One also has to consider the extra Oxygen that will be in the cylinder from HHO:
This O will displace air; which is about 78 % Nitrogen, and 2% other stuff.
So if you displace 1 litre of air with O2 you will have 800 cc more burnable O2!
Nitrogen combines with air during the combustion stroke in an endothermic reaction. (heat used up)
This robs power from the engine, but also keeps temps within design specs.
The best way to get HHO to act more like air in a std. engine is probably the addition of water mist, as already used in Turbocharged Gasolene Engines, etc.
