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Firing order for an engine is picked in the most efficent way to reduce vibrations and improve the engine balance. Most straight 4 cylinder engines use the 1-3-4-2 configuration.

So why, according to wikipedia, 1-4-2-3 was never implemented in any straight 4 cylinder engines? The cylinders firing are even further apart than the one currently used.

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  • 1-2-4-3 is essentially the same as 1-4-2-3. So, in theory it actually has been implemented. In actuality it has hasn't been.
    – DucatiKiller
    Feb 8, 2017 at 2:14

2 Answers 2

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It's because of the design of the crankshaft. If you look at the inline 4-cyl engine, the crankshaft is a flat plane crank, meaning the throws are 180° out. With that, two cylinders are on one side of the crank and two cylinders are on the other side of the crank with five (usually) main bearings holding things in place. The "typical" design of the four cylinder is to place cylinders 1 & 4 on one side and then 2 & 3 on the other side of the crankshaft. Since 1 & 4 always fall on the same side (pistons will be at top dead center (TDC) or bottom dead center (BDC) at the same time always), they cannot follow each other in the firing order. Due to this there can only be two different firing orders which work: 1-3-4-2 and 1-2-4-3.

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It's possible

But only if the crankshaft is cross-plane as opposed to the traditional flat-plane design which Paulster2 alluded to in his answer.

Cross-Plane Crank

Firing Order 1-4-2-3

The diagram above shows a 1-4-2-3 firing order (ignition event denoted by the star next to the TDC of each sinusoidal):

1. Cyl #1 fires at crank angle 0°
2. Cyl #4 fires at 180° (180° after previous cylinder)
3. Cyl #2 fires at 450° (270° after previous cylinder)
4. Cyl #3 first at 630° (180° after previous cylinder)
5. Cyl #1 fires at 720° ( 90° after previous cylinder), start of a new cycle
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  • Great answer, thank you. Never realized that a piston in motion creates the sine wave when graphed against time
    – method
    Feb 8, 2017 at 8:00
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    @method the x-axis is actually crank angle.
    – Zaid
    Feb 8, 2017 at 8:16
  • The piston motion is not sinusoidal - you need a scotch-yoke mechanism for that - used in a laboratory for that reason, not used in manufacture as friction losses are much higher.
    – Solar Mike
    Feb 8, 2017 at 9:43
  • @SolarMike are you talking about crank offset?
    – Zaid
    Feb 8, 2017 at 9:46
  • @SolarMike assuming you're talking about crank pin offset, the plot above is assuming zero offset. When offset is present, the sinusoidal waveform does a decent approximating piston travel with respect to crank angle.
    – Zaid
    Feb 8, 2017 at 10:20

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