Abstract: A spark ignition internal combustion engine (1), in particular an Otto-cycle gas engine, with at least one ignition device (14) per cylinder (2), wherein at least one piston (4) has a recess (8) in the piston head and wherein the recess (8) in plan view on to the piston head is of a substantially heart-shaped shape which differs at least in a region-wise manner from a circular shape, wherein the shape of the recess (8) in a plan view on to the piston head has precisely one axis of symmetry (10).

Abstract: A sparking plug with a central electrode insulated in respect of the plug screw-thread and with earth electrodes which are electrically connected to the plug screw-thread, there being at the combustion chamber end of the central electrode an attachment part which consists at least partially of platinum or a platinum alloy, the spark gaps being disposed between it and the earth electrodes which extend to it from the side. According to the invention, the attachment part takes the form of a prism, the top surface of which faces the combustion chamber. Furthermore, the earth electrodes extend laterally alongside the side faces of the substantially prismatic attachment member parallel with the edges of top or base surfaces of the prism. This ensures considerable stability and low burn-off. Furthermore, the electrode gap can easily be adjusted.