It might seem strange to be injecting water into an internal combustion engine, however there are several benefits to doing this. This is not new and was used in WW2 fighter aircraft to increase peak power during combat. Heat is the major problem in engines. It quickly damages engine components and is often the limiting factor in extracting the maximum performance. Combustion temperature can easily exceed 2000 degrees F, especially at high turbo or supercharger boost.
Water injection cools the flame and thus permits much higher boost settings for higher power output.
Fine droplets of water explode into steam during combustion. This dramatic volume increase helps power the engine while at the same time quenching the flame temperature. First some background. When fuel burns only the fuel vapor burns. Liquid fuel droplets don't combust and so don't contribute to powering the engine.