Figure 3-5. - Relationship between torque and horsepower.

(intake, compression, power, and exhaust). The two-stroke-cycle engine completes a cycle with just one crankshaft revolution. With diesel engine cycles (two- and four-stroke), the event of fuel injection will be shown on the timing diagram instead of spark ignition, which is common to gasoline engine operating cycles.

Four-Stroke-Cycle Engine Timing

Figure 3-6 shows a typical timing diagram for a four-stroke-cycle diesel engine. The actual length of the strokes shown and the beginning of fuel injection will vary a few degrees in either direction, depending on the specific manufacturer's recommendations. Follow the events in this cycle by tracing the circular pattern around two complete revolutions in a clockwise direction.

Figure 3-6. - Typical timing diagram of a four-stroke-cycle diesel engine.