Hi Donald

Its Because i calculated an injection timing of only 2ms

I calculated like this:

At 7000 rpm you have in a four cycle engine 3500 injections per injector. ( Rpm / 2 rotations per complete 4 cycles )

This gives us 58,3333 injections per second (Injections per minute / 60 seconds)

Than this mean that every 0,01714286 seconds you have a new injection ( 1 second / 58,33 injections per second)

I than divided this by 4 because there is 4 cycles and that gave me 0,004285717 seconds or 4,2 ms to complete each cycle

I considered than that in my injection cycle you will inject only during half of the movement when the piston is coming down so i divided it again by 2 so 2 ms

Than i calculated 1 second / 0,002 = 500 than i multiplied this for 7,4 ul and i got the result that if the solenoid remain open for 1 second 3,7ml of water would flow.

I did this to simplify the question

How much pressure must a bomb develop or must be developed inside a water tank to make 3,7ml of water to pass thru a hole of 0,4mm diameter every second.

This will tell us the pressure we need to keep inside the tank or the pump pressure we are going to need for we can get the injector to work.

The speed the water will reach is easy to calculate:

The hole having 0,4mm of diameter and for say 6 cm of length give us a volume = to 0,0075396ml so if we are going to fill it with 7,4ul of water in a cycle of 0,002 seconds this mean it will fill 0nly 98% for each cycle. but this means that water will need to run over 6cm in only 0,002 seconds. than is easy I got 6/0,002*0,98 and that gave me the resultant water speed 2944 cm per second. This is only the start!

The formula was actually water speed = length in cm divided by injection time in seconds*(volume of water to be injected - volume of the hole (tube...))

The volume of a cylinder in ml is = 3,14*((Diameter in mm/2/10)^2)*length in cm

Hope now is clear =)