Four-Stoke Cycle:

In a four-stroke engine the camshaft is geared so in which it rotates at half the speed of the crankshaft (1:2). That means in that the crankshaft has to make two complete revolutions before the camshaft will complete one revolution. The subsequent section will elaborates a four-stroke, commonly aspirated, diesel engine having both intake and exhaust valves along within a 3.5-inch bore and 4-inch stroke along with a 16:1 compression ratio, as it passes by one complete cycle. We will begin on the intake stroke. All the timing marks provided are generic and will vary from engine to engine.

Figure: Scavenging and Intake