Water injection is of no real hp benifit by itself. It was used in conjuction with other fuel enhancments to produce additional hp. In the case of the P47 Thunderbolt, it used additional fuel an alcohol injection with the water to produce additonal power. This "combat only" hp rating could only be used for approxamatly one minute of total flight time. Again.........the water was nessarry to keep the engine from comming apart due to the high manifold pressure of the huge turbocharger and added fuel to produce a tremendous boost in p[ower. The water injection dosen't add any real hp gain by itself.....it just allows you to push the engine performance with other things like air boost and fuels.
Some current rides: 73 Yamaha RD 350, 85 Yamaha RZ 350, 79 Yamaha Daytona, 82 Honda V45 Sabre, 03 Aprilia Tuono Racing, 02 Honda VTX 1800C, 06 Yamaha YZF-R1 Anniversary (LE Paint Scheme), 06 Yamaha YZF-R1 Anniversary LE (The Real Deal), 02 Suzuki GSXR 750 Track Day Only Bike, 08 Honda Goldwing Airbagger