On a 4-cylinder engine that has a firing order of 1342, if number 1 cylinder is on the exhaust stroke, what stroke is number 3 cylinder on?
A) intake B) compression C) power D) exhaust
The Correct Answer and Explanation is:
The correct answer is B) compression.
Explanation:
In a four-stroke engine, each cylinder completes a full cycle (intake, compression, power, and exhaust) in two full rotations of the crankshaft. The firing order of a 4-cylinder engine dictates the sequence in which the cylinders fire.
In this case, the engine has a firing order of 1-3-4-2. This means the ignition sequence is:
- Cylinder 1 fires first
- Cylinder 3 fires second
- Cylinder 4 fires third
- Cylinder 2 fires fourth
The key to answering this question is understanding that in a four-stroke engine, only one cylinder is firing at any given time, while the others are in different stages of their cycle.
- Cylinder 1 is on the exhaust stroke, which means it has already fired and is expelling exhaust gases. The exhaust stroke occurs after the power stroke, where the exhaust valve opens to release gases from the combustion chamber.
- Since the engine is in a four-stroke cycle, after Cylinder 1 completes its exhaust stroke, Cylinder 3 will be on its compression stroke. This is because the exhaust and intake strokes are opposite for cylinders in a four-cylinder engine. After the exhaust stroke (where the exhaust gases are expelled from the cylinder), the next stroke is the compression stroke. On the compression stroke, the intake valve is closed, and the piston moves upward to compress the fuel-air mixture, preparing it for ignition.
The firing order and the position of the cylinders during the engine cycle:
- When Cylinder 1 is on the exhaust stroke, Cylinder 3 will be in the compression stroke.
- This alternating cycle continues for the other cylinders as per the firing order.
Thus, while Cylinder 1 is expelling exhaust gases, Cylinder 3 is preparing the fuel-air mixture for combustion by compressing it.