Abstract: For optical detection of the velocity of gas bubbles in the cooling liquid of an internal combustion engine, light is radiated into the coolant by means of at least one emitter, and the scattered light caused by the gas bubbles, or rather, the change in intensity of light radiation emitted into the coolant, is measured by an optical sensor. The scattered light or intensity change is measured in at least two adjacent areas, and the velocity of the bubbles is determined from the travel time between the measurement signals.

Abstract: A measuring device is provided with a piezoelectric measuring element which is positioned between two force-transmitting supports and exhibits anisotropic thermal expansion and lateral extension behavior relative thereto in a plane normal to the direction of force application. The piezoelectric measuring element, or the end regions of the two supports adjacent to the piezoelectric measuring element, are divided into several rod-, roller-, or rib-shaped elements, the two supports and the piezoelectric measuring element exhibiting essentially the same thermal expansion or lateral extension in longitudinal direction of the rod-, roller-, or rib-shaped elements.

Abstract: In order to optimize combustion in a four-stroke spark-ignition engine with direct fuel injection, the conditions of charge flow are improved by providing the top surface of each piston with an essentially U-shaped guiding rib, which is open towards the exhaust side of the combustion chamber, fuel injection taking place into the concave area inside the guiding rib. The nozzle opening of the fuel injection device as well as the ignition source are positioned in the area of the cylinder center, i.e., preferably on different sides of the longitudinal center plane of the engine.