Low pollution emissions of stratified-charge engines and fuel economy of Diesel engines were incorporated into a stratified-charge Diesel engine with direct fuel injection. Tests and evaluation of this engine form the basis of the investigation.The paper is divided into two main parts. The first describes particular components and parameters: combustion chamber, injection jets, combustion air spin, timing, partial carburetion during optional gasoline operation, and throttling of intake air. The second part discusses these individual topics in light of the test results. The following conclusions were reached:- the spark-plug should be located close to the injection jet- exhaust emissions and fuel consumption depend on the direction of the fuel injection spray- The optimal fuel jet is a two-hole design derived from one-hole models- low combustion air spin yields poor performance- within limits, timing of fuel injection and ignition may be independently fixed; such timing can optimize fuel consumption and nitric oxide emissions- limited throttling of intake air can reduce pollutant emissions with little reduction of performanceOptimal timing of such engines would entail considerable expense.