Firing order, and what it does to the sound
A firing order is the sequence in which cylinders fire. It decides when each exhaust pulse leaves, and that timing is most of what you hear.
Why engines have one
Cylinders are numbered along the block. Firing them in plain number order would load one end of the crank and then the other, so makers pick an order that spreads the work along the crank and between banks. The crank's shape limits which orders are possible.
Even and uneven gaps
Most engines space firings evenly: 720 degrees divided by the cylinder count. That gives a steady pulse train and a clean note. Some do not. A 45-degree V-twin fires, waits 315 degrees, fires, then waits 405. That gap is why it lopes.
Firing orders in the simulator
| Layout | Order | Gaps, degrees |
|---|---|---|
| Inline-4 | 1-3-4-2 | 180, 180, 180, 180 |
| Cross-plane V8 | 1-5-4-8-6-3-7-2 | 90, 90, 90, 90, 90, 90, 90, 90 |
| 45° V-twin | 1-2 | 315, 405 |
| Flat-6 | 1-6-2-4-3-5 | 120, 120, 120, 120, 120, 120 |
| Inline-6 | 1-5-3-6-2-4 | 120, 120, 120, 120, 120, 120 |
| Flat-plane V8 | 1-5-3-7-4-8-2-6 | 90, 90, 90, 90, 90, 90, 90, 90 |
| Inline-5 | 1-2-4-5-3 | 144, 144, 144, 144, 144 |
| Flat-4 | 1-3-2-4 | 180, 180, 180, 180 |
| V10 | 1-6-5-10-2-7-3-8-4-9 | 72, 72, 72, 72, 72, 72, 72, 72, 72, 72 |
| V12 | 1-7-5-11-3-9-6-12-2-8-4-10 | 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60 |
| Inline-3 | 1-3-2 | 240, 240, 240 |
| Single | 1 | 720 |
| Twin rotor | 1-2 | 180, 180 |
| 2-stroke triple | 1-3-2 | 120, 120, 120 |
| Turbo diesel I6 | 1-5-3-6-2-4 | 120, 120, 120, 120, 120, 120 |
The two-stroke and rotary rows fire every turn, so their gaps add up to 360 rather than 720.
Try it
In the builder, tap two cylinders to swap them and listen. On an engine with one exhaust the note barely moves, because the pulses are still evenly spaced in the one pipe. On an engine with two pipes it can change a lot, because each pipe now gets a different rhythm. That is the real lesson of firing order: what counts is the pattern each pipe sees. The cross-plane V8 is the classic case.