As for "size" of the turbo, yes, I was referring to the internal Volume of the turbine housing as well as diameter of the turbine wheel. When talking about "size" of the turbine side of a turbo, two elements are at play. First is the diameter of the turbine wheel, which as you would suspect, affects the cross sectional flow area that the hot exhaust gasses escape through. Second is the A/R of the turbine housing, which is basically the angle of incidence with which the exhaust gasses first contact the turbine wheel. A small A/R (high angle of incidence) means the exhaust gasses need to make a more dramatic change in direction before exiting the turbine housing which causes restriction, but also supplies more torque to the turbine wheel to accelerate the turbo. On the flip side, a large A/R (low angle of incidence) means the exhaust gasses do not have to change direction as abruptly, but also do not put as much torque on the turbine wheel. A small A/R is good for quick spool at the expense of flow capacity, where as a large A/R is the opposite. The TD05H has both a larger diameter turbine wheel, and a larger A/R than the stock TD04HL range of turbos, which explains both the higher rpm performance as well as the freer breathing engine.
On a side note, the S60R that we will be using for prototype testing of the R32 kit will arrive tomorrow morning and install should start tomorrow afternoon. I'll be sure to keep MVS updated!
of this beast. The car is a 120K mile 744 SE that is in all original paint and trim.