Huh, what a funny way to go about it. I normally dump in racegas and then crank the boost until it won't go any higher.
I seem to have HG issues when I just crank the boost till it won't go any higher, the most I have seen with an H1C personally in my own vehicle is 52psim and it was ~83psi drive. That combined with the nearly 2000 degree egt's makes for very short lived HG's. I have heard of guys getting close to 60psi out of them though. I would love to see the kind of numbers a D would put down @ 50psim from an H1C though.
So if the turebine and or manifold becomes a retriction... how inneficient does it have to get before Boost starts to fall off.....
In my experience, this very's from turbo to turbo, and from setup to setup, but I have been as high as 2:1 drive pressure to manifold pressure respectively, and boost was still climbing. I have yet to be able to make it fall off. I need to find someone with a chipped stock 1.8T as they are known for the tiny turbo that chokes and falls off. This maybe more due to the fail of an internal wastegate then actual turbo choke though?
In my world of diesel, where you have pulling class's limited to charger inlet size (2.6", 2.8", 3" are all common class's) they run these chargers for all they are worth. There are pulling chargers in singles that will make close to 100psi, these typically are a non wastegated setup. Now guys with street chargers or 2.6" class chargers, typically run wastegates, and because most after market wastegates only have springs readily available up to ~25psi, and from again my experiance when you get about 40psi drive on a 25psi spring it push's it open.
So to combat this early opening you can either use: Boost pressure to the top port this only works for a bit till the drive pressure overcomes that as well, or drive pressure to the top port to help keep the gate closed until the desired pressure is hit, or run the wastegate completely on drive pressure, or higher budget race setups run closed loop c02 activation. This seems to be true of most gates is that as you get above 1.5:1 - 1.7:1 drive to pressure to rated spring pressure, the wastegate is starting to be forced open. So if for example: You had a 10psi spring, this would mean that by 15-17psi you would start to loose some of your drive pressure out the wastegate. Or if you had a 14 psi spring by 21 - 24psi drive you would start to see some loss.
Now to clarify this the only way you will get to 25psi on a 14psi spring is with some sort of boost controler, that will keep the wastegate from seeing the boost till you reach the 25psi. Again IMHO I think this is where you see a lot of setups that the boost falls off on there race tune is that they have a 7psi spring in the wastegate and then use the MBC or EBC to bring in the rest of the boost.
Ok let's bring this back to gasoline and it's counterparts, I know that there was a video recently of a DSM that runs a BW S372 @ 88psi. I can only assume that they ran it to that kind of pressure, because they were still making more power as they added psim.
Thoughts???