To meet the demand for improved light duty power plants a number of new developments are occurring. This paper describes some of the activities of the Ricardo research and design organization involved in these developments, including new combustion chamber designs for both gasoline and diesel engines as well as studies of multi-fuel engines to operate on fuels of differing quality that may be available in the future. Special techniques for measuring parasitic friction with torque meters and air motion by Laser Doppler Anemometry also required the development of High Speed Data Acquisition equipment. Improved design techniques based on computer aided design, computer aided analysis and finite element analysis will allow the optimum solution with current materials. In addition future engine development will require the consideration of alternative construction materials such as ceramics, composites and new inorganic materials which are all under investigation.