Water injection decreases the possibility of detonation by lowering the combustion chamber temperatures and increasing the effective "octane" of the fuel. This allows the engine to run a higher boost and full spark advance without the use of race gas. Additionally, if the water is atomized in the intake stream, there is an additional cooling of the intake charge. Both effects are increased with the inclusion of 50% alcohol to the mix (don't spray the exterior of an intercooler with alcoho!, this refers to internal injection only). The additional fuel of the high octane alcohol will in turn allow boost beyond what the factory fuel system can deliver. Water injection also has the effect of "steam cleaning" the combustion chambers and exhaust valves. This removes the carbon build up that decreases efficiency and leads to pre-ignition(detonation). It will also keep the throttle body and interior of the intake manifold much cleaner than normal.ive read this article on the net. already had the diagram & all stuff ready, but before i work on this project i wanna ask opinion from sifu's... is there any disavantage of water injection? ive done the extractor wrap last week & wonder, if it will clash on eachother since the extractor wrap is to keep heat in the extractor guess the heat will also keept in the cylinder & the water injection will cool it down.. hehehhe really confius with this..