On the supra motor with its very good set of heads and high rpm window a small turbine wheel with a small ex housing is creating too much back pressure going larger made more power everywhere.A Supra online did a nice G30-770 (58/55) in a V band .61 vs .83 vs 1.01 and it was crazy how the .61 spooled slower and made way less torque and power on higher boost, big cubes mega choke in the smaller housing even on small wheels.
Go to 8:30ish, the above dyno comparison is there. Curious what you think and have seen.
duck://player/qvSibDP902k
Those turbos they chose are the bottleneck for that motor due to not enough turbine wheel.
The exhaust housings can only do so much.
in that case the larger ar allowed for the turbine wheel to max out as a 1.01 ex housing cannot be maxed out by a turbine wheel that small.
The shaft speed was at its max from what they said but I can't see where the iats are to see what the compressor is doing.
those guys are looking at backpressure changes (they use the word choke) but doing it on a dyno and did alot of swapping parts when they could of found that result just with a sensor

Compressor size changes volume if backpressure is in a certain range.
The motor has to be able to move the volume.