0.9mm nozzle is it to big
 

my water injection is set up on a vehicle running 1.5 bar overboost and holding 1.25 bar, ihave been told i have a 0.9mm nozzle ie black/white ring, how do i work out this is the correct size or if anuyone could guide me as to which would be the best size
its used to charge the inlet charge so nozzle is located just after the intercooler exit
also can 2 nozzles be used togethe ie one for charge cooling and the other for piston crwon cooling by locating the jet in the tophat the top hat is found above the throttle body on my turbo engine

Depends on what injector duty cycle you are running. If you agree that mixture to fuel amount ratio should probably be between 10-15% as RichardL usually suggest as a good ball park figure, then you can calculate if its in there.
Also depends on your system how to calculate. I run 4 x 660cc injectors with a 2d system that injects at a constant rate with the fuel injector (if the injector is at 80% duty cycle, then so is the mixture injection amount). With my one .9mm nozzle, I am at about 12,5 % mixture-fuel.

All gathered by reading the forums :D