Process and device to measure volume in order to determine the compression ratio of an internal combustion engine

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. In contrast to other known methods, the process makes it possible to determine the compression volume reliably without the need of dismounting the engine or sealing the combustion chamber.

Dependencies are inferred from the claim text.