United States Patent 5718194
http://www.freepatentsonline.com/5718194.html

An environmental accommodating, reduced NOx, spark or plasma ignited, reciprocating, multi-fuel engine utilizing direct, in-cylinder water injection and an optional oxygen enriched air supply is able to operate as an ultra-lean burn, high compression ratio engine for notable power output and increased efficiency. The in-cylinder low-temperature water injection promotes numerous desirable effects. One, the in-cylinder water injection during compression stroke significantly lowers compression temperatures through the latent heat of vaporization of the liquid water to the gaseous form. The lower temperature of compression permits increased compression ratios while avoiding pre-ignition. As well, the low-temperature water injected air/fuel or enriched O.sub.2 /air/fuel mass demands less work in the compression stroke thereby increasing overall engine efficiency. The low-temperature water injection promotes increased mass flow through the engine for increased power output and efficiency. The low-temperature water injection also lowers temperature of combustion thereby lowering the formation of nitrogen oxide emissions. The optional enriched oxygen air supply can promote ignitibility and combustion flame stability in the presence of the high diluent water concentration and/or low or so called ultra lean fuel/air ratios, The process can be used on a two or four cycle engine, ignited by spark or plasma or any injection process.

 

GM made avilable SAE papers for ther Direct chamber injection , and it talks about just as injection takes place it lowers the temp. in the chamber, allowing higher comp. ratios= better efficiency and controlling deton. This is on there Genll ECOTEC engine 4 cyl.