Compression ignition direct injection internal combustion engine

A compression ignition direct injection internal combustion engine comprising at least each one cylinder, a piston and an injection nozzle, the cylinder having an inlet port for inducing rotation of the incoming air about the axis of the cylinder and a combustion chamber or cavity in the form of a body of rotation disposed in the piston and receiving almost the entire quantity of combustion air at the end of the compression stroke, said chamber having, below the crown of the piston, a constriction which divides the chamber into an upper and a lower part, said injection nozzle being mounted with the nozzle tip substantially on the axis of the chamber and with its fuel jets being directed towards the wall of the chamber, the geometrical points of intersection of the axes of the injection nozzle holes lying below the narrowest cross-section of the constriction in the chamber throughout the entire injection period, the diameter of the narrowest cross-section of the chamber dividing the upper part from the lower part of the chamber measuring about 75 to 90% of the maximum diameter of the chamber, and the upper part of the chamber lying between the plane of the narrowest cross-section and the plane of the crown of the piston having a volume of about 10 to 30% of the overall volume of the combustion chamber, the engine operating at an unusually high compression ratio whereby fuel consumption by the engine and engine exhaust of unburnt hydrocarbons and soot are markedly reduced.