Before there was modern measuring equipment, water in a tube was used to measure small pressure changes, I think it was called a manometer. The force that it takes to move water against gravity by 1" is an "iwc" of pressure. Turns out that a colum of water 28 inches high is equal to 1 psi, and there is 400 iwc in 1 atm. Example: If you have a straw in your cup of water that is 14 inches tall above the surface of the water, your mouth will have to come up with 1/2 psi of suction to quench your thirst.
The pie chart is saying that 66% of 1.07 iwc is the restiction in the mouthpiece.
1.07 iwc is not a lot of pressure, barely enough to make us blink. But the laws of fluid flow follow that if you double flow, you will see a 4 fold increase in resistance. Its an exponential relationship, resistance goes up by the square of flow rate. If you want to predict what will happen at 65 lb/min, you just do the ratio thing, 65^2/5^2=X/1.07, and solve for X. Then you would then just apply the pie proportions to X.
This is only an approximation, but experimentally, the numbers at full flow are staggering (do the math). Also interesting is that as flow rate increases, the flow characteristics in each piece of the pie are changing. The element falls to 2-3% of the total, while the mouthpiece goes from 66% to 84% of the total.
