Label the Y-axis as "Pressure," and label the x-axis as "CFM x 100." Plot your data for pressure and CFM.
Label the right side of the graph, along the y-axis, "Brake Horsepower." Plot your data for brake horsepower and CFM. This should be done on the same graph as you used in Step 1. Use a different color to avoid confusion.
Plot the system resistance curve. Ps = k * CFM2 is the formula to use. Remember that pressure increases when CFM is squared. This means your curve will be positive. With this curve you'll also be able to see the speed of the system flow.
Intersecting lines show where the operating points are.
Find the operating point by focusing on the fan curve and the resistance curve. Points along the fan curve prior to the operating point are unstable points. Anything after the operating point is considered the optimum range of operation.