water injection for turbo usually use the pressurize air (boost) from turbo to "push" water from sealed water container (with controlled vent) to inlet pipe after air filter or turbo.
appropriate nozzle to make small mist of water droplets required to make sure it "blend" with intake air.
water injection benefit from colder air intake temperature and thus some power increment can be felt.
Here's a complete walkthrough of the car, done by GT Channel, when they visited the Nissan Heritage Garage not long ago. The Nissan Skyline GT-R was...