I got around to pulling apart a stock turbo last night, the Turbine wheel has an inducer size of 35mm, an exducer size of 40mm and an A/R of approx 0.35-.45 (difficult to measure)
The compressor has an inducer of 32mm, and an exducer of 45mm, approx A/R of 0.45.
These figures are quite close to this turbo http://www.turbobygarrett.com/turbob...4_454082_2.htm which is rated at 150hp by Garrett.
The most interesting thing I discovered was that the turbine side is only rated at 6.3lbs/min of airflow, and the compressor can stretch all the way to about 14lbs/min, but the efficient point is about 10lbs/min (at about 1 bar)
Compare this to a GT2860R http://www.turbobygarrett.com/turbob...R_707160_7.htm which is the model of turbo I'm considering going with, it flows 16lbs/min on the turbine side, but it is most efficient at about 17lbs/min on the compressor, and can stretch all the way up to 30lbs/min
If you compare the ratios, to me it sounds like our turbos are heavily limited by the turbine, which is further reinforced by the fact that my rebuilt and upgraded turbos haven't had the compressor wheel modified at all, but the turbine wheel has been completely re-done with different shaped blades and a larger inducer. This implies that the limitation is the turbine side.
Thoughts?