The compression stroke now takes place with the piston moving from right to left, the compression pressure reaching a maximum at F. Ignition occurs slightly before the point of greatest compression, at I, and the expanded gas increases in pressure until the point A is reached. From this point the same cycle of events is repeated. Because of the dilution of the charge by the burnt gases of the preceding combustion, the mixture burns slowly as will be seen from the inclined combustion line FA. Due to this delayed combustion, the piston travels the distance S on the working stroke before the pressure reaches a maximum. This diagram is typical of the small marine type of two stroke cycle engine which has no further scavenging than that performed by the rush of the entering mixture. The diagram of the pressures and vacuums in the crank case are similar to those of suction and compression in the four stroke cycle type. (39) Diagram of Diesel Engine. A diagram of the Diesel engine is different in many particulars from that of an ordinary gas engine, as will be seen from the diagram in Fig. 14. The pressures rise in an even, gradual line from the end of the compression curve, and instead of having a sharp peak at the end of the combustion, as in a gas engine, the top of the curve is broad and greatly resembles the indicator diagram of a steam engine. The compression curve constitutes a greater proportion of the pressure line than that of a steam engine, the rise of pressure due to the ignition being very slight in comparison to the height of the compression curve. There is no explosion in the usual sense of the word, only a slight increase in pressure as distinguished from the rapid combustion in the gas engine. Starting at the beginning of the compression stroke at H, the pressure of the pure air charge increases to about 500 pounds to the square inch at I, the point at which the fuel is injected. From I to C is the increase of pressure due to the combustion. The pressure stays at a constant height from C to D as the fuel supply is continued between these points, and is cut off when the piston reaches the position D. It will be seen that the admission of the fuel through the distance A covers a considerable proportion of the working stroke, and that the points of fuel injection and ignition are coincident. From the point of fuel cut-off at D expansion begins and is continued in the usual manner to F, the point of release. When the load is increased, the period of oil injection is also increased, the other events remaining constant. Should the light load require an oil injection period as shown by A, the greater load would require injection for the period B. In the latter case, the expansion line would be EG, which would produce a diagram having a greater area than the line DF, and there would be a great increase in the release pressure GH as well.