The paper covers exploratory development of the Rotating Combustion (RC) engine spark ignited stratified charge versions since 1966. Configuration improvements resulting in increased power and reduced fuel consumption are described and test results cited. Exhaust emissions are presented, with and without a catalytic converter, and compared with carbureted RC engine results as well as limited diesel engine data. It is concluded that the technical bases for an efficient, lightweight, economic, low-emission powerplant capable of broad range operation have been demonstrated. Weight and displacement parametric curves are presented for one family of advanced higher speed engines.