A review of past development progress, the basic engine design problem, and the design status of today's engine indicates that the continued development of the four cycle, reciprocating piston, spark ignition automobile powerplant means continued improvements and the creation of a more difficult task for possible replacement. The years of development time have resulted in significant improvements in four areas: higher rotative speeds and improved thermal, volumetric, and mechanical efficiencies.
Continued development and refinement of this engine will be stimulated in the future with catalytic development efforts similar to one we are presently experiencing - reduction of exhaust emissions. This effort is discussed in addition to the overhead camshaft valve mechanism and aluminum engines which are also subjects of current development interest.
