THE logarithmic diagram lends itself peculiarly to the study of cylinder conditions and to the quick determination of the changes taking place. Although some use has been made of the logarithmic diagram for indicator-card analysis, its use has been rather limited. Much more can be learned by this means than is usually done.
Not only can valve and combustion events be determined; cylinder temperatures can also be found. It will be shown that the cylinder temperatures can be found directly by measurement in the logarithmic diagram, thus obviating any necessity for calculating them.
Curves of internal energy versus temperature make it possible to find the internal energy of the charge at any point, once the temperature is known. It is therefore a relatively simple matter to follow the flow of energy throughout the cycle. A complete picture of the events taking place in the cylinder can thereby be obtained, affording a ready means of studying engine performance.
Examples are given showing the application of the logarithmic method of analysis to several different kinds of indicator cards. These examples indicate that practically any type of indicator card can be analyzed completely in a short time by means of the logarithmic diagram.