The firing order of a 4-stroke engine refers to the specific sequence in which the cylinders undergo the four strokes of the combustion process (intake, compression, power, and exhaust). Here's a general overview of the firing order procedure:
1. Intake Stroke:
- The intake valve opens, allowing air and fuel mixture (gasoline engines) or air alone (diesel engines) to enter the cylinder.
- The piston moves downward, creating a vacuum that draws the mixture/air into the cylinder.
2. Compression Stroke:
- The intake valve closes, and the piston starts moving upward, compressing the air-fuel mixture or air within the cylinder.
- This increases the pressure and temperature of the mixture.
3. Power Stroke (Combustion and Expansion):
- Just before the piston reaches the top of the compression stroke, the spark plug ignites the compressed air-fuel mixture (in gasoline engines) or the high temperature and pressure cause spontaneous ignition (in diesel engines).
- The combustion process generates heat, causing rapid expansion of gases.
- The expanding gases push the piston downward, generating power and driving the crankshaft.
4. Exhaust Stroke:
- As the piston nears the bottom of the cylinder, the exhaust valve opens.
- The piston continues moving upward, pushing the burnt gases out of the cylinder and into the exhaust system.
- The exhaust valve remains open until the piston reaches the top of its stroke.
The firing order determines which cylinder undergoes each stroke at specific intervals. For instance, in a 4-cylinder engine with a 1-3-4-2 firing order, the cylinder numbers indicate the sequence in which the power stroke occurs. So, cylinder 1 fires first, followed by cylinder 3, then cylinder 4, and finally, cylinder 2. This pattern repeats continuously as the engine runs.
The specific firing order of an engine is designed to optimize performance, balance engine vibrations, and ensure smooth operation. It is determined based on various factors such as engine design, cylinder arrangement, and desired power characteristics.
