Water injection was evaluated scientifically in the 1930's by H. Ricardo who demonstrated that one can basically double the power output of an engine using water/methanol. The first widespread use was during WWII on supercharged and turbocharged aircraft. In 1942, the German Luftwaffe increased the horsepower of the Focke-Wulf 190D-9 fighter aircraft from 1776HP to 2240HP using 50:50 water/methanol injection. The allies soon followed by fitting the P51 Mustang and other high performance aircraft with water/methanol injection. Following the war, the turboprop aircraft industry used water/methanol injection and called it the "automatic power reserve system (APR)" for use in hot or high altitude take off. It surfaced again in the 60's when GM used a system on the OEM turbo Corvair. It was used effectively in Formula 1 before being banned for adding too much power.
The latest competitive use is in World Rally Racing (WRC) where virtually all teams use it in some form and in diesel truck/tractor pulling competition. It is important to note that in the fall of 2004, the long standing world record in the quarter mile for diesels was broken twice (now 7.98 sec) by two different vehicles; both using the Boost Cooler® water/methanol injection system by Snow Performance