The Junker two stroke cycle engine stands unique among the large stationary units not only in the principle of its working cycle but in its construction as well, and while it may be considered freakish when compared to standard practice it has proved its value in many European installations. The combustion occurs in the center of an open ended cylinder between two pistons that are forced in opposite directions by the expansion of the gas, and as there is a single acting piston in each end of the cylinder at the end of the stroke, there is no need of stuffing boxes, cylinder heads or valves. It is apparent that by moving the pistons in opposite directions, the effective piston velocity is twice that of the actual velocity of either of the pistons, and that it is therefore possible to gain a high heat efficiency at high piston velocities with a low rate of rotation. The double pistons increase the scavenging effects, reduce the losses to the cooling water and increase the efficiency at light loads. A marked reduction in weight over the four stroke cycle engine is made possible because of the absence of valves and valve gear. This engine is of the injected fuel type that is the fuel is sprayed into the combustion chamber after the completion of the compression stroke in a manner similar to the Diesel engine. By prolonging the injection of fuel after the piston has started on the outward working stroke it is possible to maintain the maximum pressure due to the combustion for a considerable period. This gives an indicator card that is very similar to that of a steam engine as the flat top of the Junker’s card due to the continued combustion and pressure corresponds to the admission line of the steam engine. As ignition is caused by the high temperature of the compression, almost any low grade oil may be used even down asphaltum oils and coal tar. [Illustration: Fig. 8. The Junker Two Stroke Cycle Engine. ] In Fig. 8 five piston positions corresponding to five events are shown by the diagrams a, b, c, d, e. From the diagrams one may also get an idea of the arrangement of the principal parts of the engine and their relation to one another. P and P2 are the two pistons, C the open ended cylinder, G the connecting rod of the inner piston P, H-H the two connecting rods of the piston P2, I-I the side rods of the piston P2, and V is the three throw crank shaft which is acted on by the three connecting rods H-H-G. The piston P2 is connected to the side rods through the yoke Y. It will be noted that the crank throws controlling the piston P2 are 180° from the crank connected to piston P, which causes the pistons to move in opposite directions.