Even from the original design, I have used water injection to cool the intake air temperature entering the cylinders(increasing the air density) and to slow the fuel’s combustion to help prevent detonation. While it is not a necessary component of the turbocharger system, it allows for higher boost pressures which generate more power.
In the initial turbocharger system design phase, I considered an air to air intercooler, but, as on any motorcycle, mounting space is limited. An intercooler that would provide substantial charge air cooling would be large in size and difficult to mount and duct air through.
Water injection components are very small and can be hidden around the bike making it easier to incorporate on a motorcycle. I purchased an Aquamist 1S water injection system and it worked great until the pump failed in September 2012. Aquamist no longer manufactures or supports their ole race pump, so I have changed to a Devil’s Own water injection pump but still use the Aquamist jetting. I am currently using the first water reservoir I designed, which has a .5 gallon capacity. The tank needs refilling every 4-5 fuel stops, which is easily manageable.The water injection pump is activated by the Turbosmart e-Boost 2 boost controller at a programmed manifold pressure.
There is lots of discussion in the forced induction world about the differences between running water only verses a water/methanol mixture. I prefer running pure water since it is easy to find and is not harsh on o-rings and seals like methanol and mixtures can be. Methanol provides better intake charge cooling while lowering the freezing point of the mixture, making it a great solution for water injection systems that live in freezing climates.
For the last side-mounted turbo setup I ran in 2008, I made a 1.5 gallon tank that mounted below the motor. It was very easy to fill and rarely need refilling, but I could not use it with the new turbo design.