The wastegate bypass cross section will dictate the lowest setting possible. Remove the actuator arm and hold it wot all the way through 3rd. Whatever boost it makes is the minimum it can make. Doesn't matter what controller is used. You will need a large bypass to run only 10psi unless you are running close to a stock turbo. Usually a very light spring (in an external gate) with an external source of pressure and a good smart electronic controller is required to have a wide swing of adjustability. You can open the bypass up to whatever size puck you have and then buy a few plates with no hole. Then you can make multiple plates with multiple hole sizes. The bigger the hole the lower the boost with any given wastegate tension. Big hole with light tension equals low boost. Small hole with heavy tension equals high boost. Trying to go below 70% of the mass flow potential of a turbo requires a very large bypass typically. The cracking point of the puck can be calculated if you know the spring tension, actuator diaphragm cross section, actuator pressure, leverage (or lack of), cross section of the puck, and exhaust pressure. There's no set in stone 1 turn equals 1 psi or any other internet fantasy. With my turbo all in I can still shorten the rod 5 more turns yet it doesn't matter because the tension is so high and the exhaust pressure not high enough to overcome it even with the pressure port on the diaphragm plumbed off the compressor cover where it's hitting the actuator with the highest possible pressure.
If it takes 40psi of exhaust pressure to spin a turbine to flow 70lbs/min of air on the compressor side then there has to be a minimum mass flow to create the 40psi. The difference would be what needs to be wastegated to prevent over boost not taking into account mechanical limitations like the hub bursting from over speed
BPE2013@hotmail.com