defines therewith and with the upper end of the piston an enclosed variable volume combustion chamber 19 inlet and exhaust valves 20 and 22 respectively control ports not shown for admitting a swirling charge of induction air to the cylinder on the piston intake stroke and exhausting burned gases from the combustion chamber on the piston exhaust stroke engine 10 further includes fuel injection means in the form of a high pressure cylinder fuel injection system the injection system includes an injection nozzle 23 mounted in the cylinder head and having a spray tip 24 extending into combustion chamber 19 through which charges a finely atomized high pressure fuel spray are injected into the combustion chamber an ignition system is also provided that includes a spark plug 26 for each cylinder mounted in the cylinder head and having a spark gap 27 located within the combustion chamber in the path of the fuel spray the engine also provides in each combustion chamber a catalytic grid 28 which may be in the form of a stainless steel wire mesh or screen coated with a suitable catalyst such as platinum other forms of screens and other catalysts may be utilized within the scope of the invention the catalytic grid 28 is fixedly attached to a suitable portion of the cylinder head in the disclosed embodiment it is shown welded to the body of the spark plug 26 and extending into the combustion chamber to be received within the piston recess 15 as the piston moves upwardly to.