Hey Startto,
I edited my post to reflect Watts as opposed to kW, guess I wasn't paying enough attention the first time around. Sorry about that.
Power is simply the work done per unit of time or P = W/dt.
A watt is 1 joule per second which is equivalent to 1 NM/S.
So to get power in Watts, you are going to want to find out the amount of work performed in 1 second.
Using HydTools equation for RPM with your input values of 14L/min and 330mL displacement per rev and 0.9 volumetric efficiency gives roughly 38RPM.
To use RPM in the final equation, you need to convert it to angular velocity - which is where the 2*pi/60, or 9.549 in the formula comes from.
Putting it all together leads to: 900nm * 38RPM / 9.549 = 3,581.5 Watts or 3.58 kW or 4.8 hp.
Hope that helps.
Michael Hall, PE (TX) PMP - President
Engineering Design Services LLC