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All of this, however, is just to obtain the Cd of our flow at nominal flow rates. When throttling down, our flow rates will change. Since our fuel is incompressible, its Cd will remain constant when we throttle down, so we can use the same Cd for all throttle levels for the fuel. However, for the nitrous, this is not the case. This is because we are modeling the nitrous as an incompressible fluid (which it is not) and wrapping all of its flash-boiling into a very low Cd. However, the amount of flash-boiling is governed by the dP across the injector. If the dP is high, more flash-boiling will occur; if the dP is low, less flash-boiling will occur. This means that as we throttle down, our Cd will increase because the injector dP decreases, which makes the nitrous behave more like an incompressible fluid. Currently, we are thinking of obtaining Cd at a bunch of different injector dP's, and then fitting that data to a curve. If we know how Cd changes with mass flow, we can characterize our throttle valves.