Abstract: Four-stroke combustion engine comprising a cylinder block having a cylinder in which a piston can move, a cylinder head with an intake manifold whose intake opening forms part of the cylinder head, said opening being opened or closed by an intake valve and with a by-pass which is separated from the main inlet channel and has a discharge opening direct into said inlet channel, upstream of the valve, whereby besides the by-pass (2) for air in the main inlet channel (6) also an injector (1) opens into this intake manifold (6) in such a place and such a position that the center line of the fuel jet is directed at the foot of the inlet valve (5).