One of the defining characteristics of the five-cylinder engine is its unmistakable sound. It is primarily created by the unusual firing order in which the engine’s five cylinders ignite: 1-2-4-5-3. This means that both adjacent cylinders and cylinders further apart fire in succession. The uneven firing order creates irregular pressure pulses, resulting in a slight pulsation and an uneven sequence of pressure waves in the exhaust system. This, in turn, gives the five-cylinder engine its distinctive sound.
The firing order is not chosen at random. In an in-line five-cylinder engine, it results from the fundamental objective of distributing the individual combustion events as evenly as possible throughout the entire operating cycle.
In a four-stroke engine, one complete cycle requires 720 degrees of crankshaft rotation. Since a five-cylinder engine has five cylinders, this cycle is divided into five equal sections. This results in a firing interval of 144 degrees, meaning that one cylinder fires at regular intervals, producing a continuous power output.
This is made possible by the special design of the crankshaft. Its crankpins are arranged so that the pistons operate at staggered intervals and complement one another. While one piston is performing the power stroke, the other cylinders are in the remaining phases of the four-stroke cycle, such as intake or exhaust. This creates a more even sequence of power strokes, allowing the engine to run more smoothly than a conventional four-cylinder engine.
The specific order in which the cylinders fire is chosen to distribute mechanical loads as evenly as possible. Rather than allowing adjacent cylinders to fire one after another, the firing sequence is arranged to spread the combustion events across the engine. Typical firing orders include 1–2–4–5–3 and 1–3–5–4–2. This arrangement helps to balance the forces more effectively and reduces unwanted vibrations.
Overall, the combination of evenly spaced firing intervals and a carefully selected firing order results in a smooth and continuous flow of power throughout the engine.