the 61mm flows a little more than the 62-1...turbines being the same. the 61 likes higher pressure ratios. the 60-1 is known for its quick spool. the 62-1 is a little quicker than the 61.
60-1 < 62-1 < 61 < 67
it seems that if you're going with a t4 turbine, skip the 61 and go for the 67 - they spool similarly.
either the 62-1 or 61 will spool at 2800 with the t31 turbine, 3200 with t350, 3500 with p trim t4. the new hp wheels spool slightly quicker with less backpressure. and ball bearings typically take off 400 rpm.
i haven't gotten an answer as to how much quicker a .63 a/r will spool over a .85. or how much more power an s cover makes over an e cover, and how it affects spool. it depends on the motor and mods.
