There more efficient, later rotor profile design, but they are smaller so the 980 could still flow more air. As the rotors get bigger, they need more clearance between themselves and the case, so this lowers efficiency. And with later rotor designs, one of the major improvements is the ability to flow more air in a smaller given area. Example, the PSI has a much older rotor profile, although it's very good, its very similar in flow to our new 305, but our 305 is much smaller, will take less power to operate and will create lower temps.Originally Posted by knot-right
It can certainly be used for non-intercooled applications, but it's free HP in the boats so I like to always go intercooled.