The Subaru FA24DIT MGT22 Turbo is equivalent to the Garrett GT2259 Turbo and compressor graph possibly looking like the one shown below:
The FA24DIT in the Subaru Ascent run a Volumetric Efficiency (VE) of around 95% from 4400-5600rpm, dipping to less than 90% @ 6000rpm. Due to the turbo size and other engine factors, it is very efficient from 2000rpm to 4000rpm. The PR at 5600rpm from logs is 1.8 (11.5psi).
The Garrett representation could be off a little for the compressor being used and it is very possible the shape of the graph will be different and extend a little more to the right. Based on Subaru data and engine flow data, I see around 30lb/min. Given that Subaru’s tend to run rich, I would expect the flow to be around 27lb/min. That being said, I would expect the MGT22 could flow up to 32lbmin at high compressor speeds with a lower efficiency of 65% or less. That is more hot air. To achieve a flow of 32lb/min, the turbo will need to push 16psi of boost at 5600rpm. That will net 320chp or around 270whp. A good avg of 250whp could be expected on the stock exhaust system. For those searching for more torque, this can be easily had since the turbo is small, but the turbine will be spinning a little faster. That implies a little more heat and a nice water spray would help keep the Intercooler cool.
If XRT had to tune, we would run 18-20psi in the sweet spot and taper down to an efficient boost of 15-16psi at 5600rpm and obviously lower to rev limit.
A good stock upgrade for the Subaru ascent and possibly for the Outback and the Legacy when it comes out with the FA24DIT is the Garrett GTX2860R. It will operate well within the shift points of the CVT transmission.
Reference data taken from – http://xtremeracingtuning.com/2019/10/26/xrt-subaru-fa24dit-tuning/
Please see a similar car we worked on that have a similar setup and Subaru mythology – http://www.xtremeracingtuning.com/forum/viewtopic.php?f=114&t=468