thermal

The head flow seems to me as the intake side since it is based off a 66 F temperature... "standard day".

The issues I've seen with relatively smaller turbos relies on adiabatic efficiency. This can be a combination of the whole set-up.. from the compressor to the head. The problems I've seen with a smaller turbo is "volume". 10 psi on a small turbo vs 10 psi on a larger turbo can have a significant difference in power output. A 57 trim is a good all-around turbo for a B-series. Lag is almost non-existent especially if dealt by a good tuner. Plus, the potential to use it for more power later on is there.

We dynoed a stock B18a with an SC61 (non-Scover)... AEM EMS. The motor is straight up from the bone yard... from an automatic LS. All we did was opened it up to inspect. While at it, we cleaned the cylinder walls and head surface and tossed an OEM head gasket. At 10psi, it put down 255whp already. The tuner/owner of the motor wanted to see what happens at higher boost level... YES, stock everything. We were suprised that it hit 402whp at 22 psi... cant remember the torque numbers. It may have been a freak motor.... I'm not saying that it was a reliable set-up at over 20psi... I wouldnt even run that myself on a stock motor.

BAD4DR

Cool. That's why I like the 50 trim. Good power capability (30 psi capable, 500+ hp capable.) At low pressures, it seems that 57, 54, 50, and 46 trims are fairly close. The 60-1 flows better on low boost, but also runs into surge faster! Seems a bit overkill to me. The .63 A/R exhaust seems overkill for a 300 hp motor, that can achieve the same horsepower, with far better mid-range, on a .48 A/R.

But now you see the N/A builder in me coming out. Trying to optimize everything you can under the curve as you're only going to have a certain power level to play with.