A reciprocating engine with gas turbine type combustion at nearly constant pressure is being proposed for automotive application after an extensive design and computer analysis. It appears to have the expected advantages of 20–30% reduced fuel consumption and of almost complete elimination of undesirable exhaust elements leading to air pollution. It should operate well on a wide range of fuels without regard to octane or cetane number and, hence, would need to have no lead in the fuel. It should weigh little, if any, more per unit of maximum output in the supercharged condition, and it can be manufactured largely on the present tooling of the automotive industry. The overall engine envelope seems to present no problems for modern low profile motor cars. It should serve well in various numbers of cylinders and sizes throughout the present range of automotive requirements. Part II of this paper includes a comparison of automotive emissions between engines via the “adjusted-to-stoichiometric” method.