Abstract: A process and a device to measure the compression volume in a cylinder of an internal combustion engine in which process an overpressure in the combustion chamber is produced by introducing a controlled gas flow through existing spark plug or injection nozzle bores. A pressure expansion in the combustion chamber, caused by leakage of the piston rings, is analyzed. The size of leakage is determined by measuring step-by-step varied gas flows, introduced into the chamber and flowing out of the chamber through leakage, and measuring the resulting pressures built up in the chamber at a stationary state of flow and pressure. By combining the leakage characteristic and the pressure expansion characteristic the leaking volume having flowed out of the chamber during the expansion can be determined. With the knowledge of the leaking volume and the pressures and temperatures at the beginning and at the end of the expansion, the compression volume can be calculated with the aid of the general gas equation.

Abstract: A method and device for measuring combustion knocking in the combustion chamber of an externally-ignited internal combustion engine, the device comprising a magnetostrictive element with a maximum diameter of 2 mm and a length-to-diameter ratio of greater than 100, the device being mounted in the engine so as to be exposed to the combustion chamber. The device can include a coil to which the magnetostrictive element is connected for converting changes in magnetic conductability in the magnetostrictive element, due to pressure increases in the combustion chamber to which it is exposed, into electrical signals. The coil in turn can be connected to an electronic switching system for the engine.