Close collaboration between ABB and NGK enabled the development of the rotor for the Comprex(R) pressure-wave supercharger (PWS) as an extruded component in pressureless sintered silicon nitride. The ceramic rotor is lighter than the steel rotor, permitting a free-running PWS. And, the lower thermal expansion of ceramic improves the supercharging efficiency. Prototypes have been road tested since 1984 and fulfil the major engineering requirements: burst speed thrice nominal, probability of fracture ≤ 10-5, maximum temperature well above operating and low risk of damage from foreign objects. When the ceramic rotor becomes cost competitive and can be mass produced, it will considerably expand the range of applications of the PWS.