Question

Which of the following are firing order in 4 stroke 4 cylinder diesel engine?
(A) 1-2-4-3
(B) 1-3-4-2
(C) 1-2-3-4
(D) 1-4-3-2
Choose the correct answer from the options given below:

• A. (A) and (B) only.
• B. (B) and (C) only.
• C. (C) and (D) only.
• D. (A), (B), (C) and (D).

Hint:

For almost all modern 4-cylinder inline engines (both petrol and diesel), remember the standard firing orders:
- 1-3-4-2 (Most common)
- 1-2-4-3 (Alternative)
These sequences ensure that power strokes alternate evenly across the crankshaft.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The firing order of an internal combustion engine is the sequence in which the power strokes occur in different cylinders.
A correct firing order is essential to balance the power distribution, minimize engine vibrations, and ensure smooth crankshaft rotation.

Step 2: Detailed Explanation:
In a 4-stroke, 4-cylinder inline engine, the four pistons are connected to the crankshaft such that the two outer pistons (1 and 4) move in unison, while the two inner pistons (2 and 3) move in the opposite direction.
This arrangement helps balance the primary and secondary forces.
Since each cylinder completes a power stroke once every two rotations (\(720^\circ\)) of the crankshaft, the power strokes must be spaced \(180^\circ\) apart:
- When piston 1 is on its power stroke, pistons 2 and 3 are moving down (one is on suction, the other is on power).
- To maintain dynamic balance, power strokes should alternate between the front and rear halves of the crankshaft.
The most common firing orders designed for 4-cylinder inline engines are:
1. 1-3-4-2 (B): This is the most widely used firing order.
2. 1-2-4-3 (A): This is another standard alternative firing order.
Other sequences like 1-2-3-4 (C) or 1-4-3-2 (D) would cause successive power strokes on adjacent cylinders or unbalanced forces, leading to severe engine vibrations and crankshaft fatigue.
Therefore, (A) and (B) are the correct firing orders.

Step 3: Final Answer:
The correct option is (A).