WORKING OF FOUR STROKE CYCLE SI ENGINE (PETROL ENGLINE) - WEEK THREE AND FOUR

WEEK THREE AND FOUR

TOPIC : Working of Four Stroke Cycle (Petrol) SI Engine

As name implies, four stroke cycle engine operations consists of the following four strokes.

1. Suction stroke

2. Compression stroke

3. Power or expansion stroke

4. Exhaust stroke.

1. Suction/Intake stroke:

At the beginning of the stroke, the piston is at the top dead centre (TDC) and it is ready to move downward. As the piston moves downwards the vacuum is created inside the cylinder. Due to this vacuum, the air fuel mixture from the carburetor is sucked into the cylinder through inlet valves till the piston reaches bottom dead centre (BDC). During suction stroke the exhaust valve remains in a closed condition and inlet valve remains open. At the end of the suction stroke, the inlet valve will be closed as shown in Figure 1.3(a).

2. Compression stroke:

During the compression stroke, both the inlet and exhaust valves are in closed condition and the piston moves upward from BOC to compress the air fuel mixture.

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