An internal combustion power plant system provides a rotary engine and a rotary fuel/air mixture compressor for the rotary engine on a common driveshaft, coaxially mounting each end and supported between them by a gearbox which synchronizes operation of various ignition and valve and abutment components of the system; compressed fuel/air mixture is supplied to and ignited in a valve-isolated manifold chamber in the rotary engine in successive charges following which each ignited charge is valved radially into one of plural expanding chambers defined by the rotary engine rotor and abutment mechanism, where it urges rotation of the rotor and then exhausts radially; in preferred embodiment the exhaust actuates a parallel fuel-feed which booster pumps fuel/air mixture into the manifold chamber; detail improvements disclosed include designs of runners, abutments, valving and rotary compressor mechanism.