The old, original RAMs were not controlled by the ECU sensing RPM (as most modern model turbines do). The RAM ECU sensed CP, or Compressor Pressure. Andy Low built a small pressure sensor into the ECU that read the pressure at some bleed off of the compressor. The old RAM 750F was nominally about 17.5 lbs at 1300 mb of pressure. Idle was down around 90 to 100 mb.