In this chapter, we have covered the principles of operation associated with 2- and 4-stroke cycle engines and opposed-piston engines. It is essential that you fully understand the principles of operation of these engines. To do so, you must know the meaning and significance of such terms as OTTO CYCLE, THEORETICAL DIESEL CYCLE, ACTUAL DIESEL CYCLE, POWER STROKE, COMPRESSION STROKE, SCAV-ENGING, and SUPERCHARGING. This chap-ter has provided you with basic information associated with these terms. As you progress through this rate training manual, subsequent chapters will provide you with additional information that will clarify and supplement the information you have just read. It may also help you to refer to figures 2-8, 2-9, and 2-10 as you study the information in the following chapters.

Figure 2-2.Strokes and events in a 2-stroke cycle diesel engine cylinder.