The dynamic TDC assigning on the marine four stroke engine's indication diagram

Determination of the internal combustion piston engine 's indicated power is a complex task. A number of difficulties lead to lots of solutions utilized to increase the accuracy of the result. This paper reports on the experiments concerned with a four stroke engine's piston dynamic position determination. Although the paper is mostly concerned with the piston's TDC definition, the experimental methodology can be utilized in the entire piston movement determination. A specially developed measuring assembly and its working principle utilized in the experiment have been presented too. It allows the acquiring of a set of time-position coordinates. Based on the coordinates, the mathematical algorithm for dynamic piston positioning can be developed. As the piston movement was being observed from the crankcase side, the methodology proved to be relatively cheap and easier for installation, compared to proximity sensors installed in the cylinder head. The advantage of optical sensors and light pipes being used was reduction of the explosion risk in oil mist environment inside the crank case.