Combustion engine

The engine (1) has two fuel pipes (5, 6) connecting a pre-chamber (2) with a source of fat fuel-air mixture or a pure fuel, and a source of lean fuel-air mixture, respectively. The pipes are connected with the pre-chamber by a mixing device (7) for mixing the lean and fat fuel-air mixtures and/or the pure fuel. The mixing device comprises a venturi nozzle whose convergent and narrowing sections are connected with the fuel pipes, respectively. Multiple holes are arranged in the narrowing section. A divergent section of the nozzle is connected with the pre-chamber.