Normally aspirated.
A typical screen washer pump runs about 40 to 45 psi of pressure. The use of two 15 thou jets is enough to supress detonation on a 12.5:1 compression 2 liter Pinto engine running on pump regular, giving 130 net hp. This is about 14 cubic centimeters per minute per jet, or a total of an ounce of water a minute through two jets by my estimates. That's allowing an engine run 87 octane when it would need 105 octane at that compression ratio. The rise in ratio is from 8.2 or 9.2 stock, depending on the year. The idea is to under size the water injection jet, and just increase the discharge diameter with a drill and chamfer the craggs. There is no performance increase if too much water is used. Water injection just lets the engine live!
For a 200 or 250 cube engine, just start with two 15 thou jets for a 2-bbl carb, or one 21 thou jet for a single barrel. (A single jet isn't a good idea, though). Then go up or down depending on the compression rise and fuel grade. If the engine is giving 130 hp, then these sizes should be about right.
Nitrous Oxide
It is possible to add up to 50% (by volume) of the total fuel flow of an engine in water injection when N20 is used, with no loss in engine power!
Bearing in mind a stock 130 hp engine with nitrous may give well over 200 hp with a 70 hp shot of 4 pounds per minute. You then will need about 715 cc/minute, or about 18 ounces per minute of gasoline, plus the excess fuel needed to stop the nitrous leaning out. You could add over 360 cc/minute, or up to 13 ounces per minute! If you had a strong 200 hp engine to start with, and added a 100 hp kit, then obviously, there'd be a need for a massive 20 ounces per minute.
You'd need around six 38 jets just to get that on one of our sixes!
If you add alcohol and water mix, you get added power and detonation controll. It's all good!