FIRING ORDER: ITS PURPOSE AND ORDER IN DIFFERENT NUMBERS OF CYLINDERS

The firing order is the sequence of power delivery of each cylinder in a multi-cylinder reciprocating engine. This is achieved by sparking of the spark plugs in a gasoline engine in the correct order, or by the sequence of fuel injection in a Diesel engine. When designing an engine, choosing an appropriate firing order is critical to minimizing vibration and achieving smooth running, for long engine fatigue life and user comfort, and heavily influences crankshaft design.

The firing order of an engine is the sequence in which the power event occurs in the different cylinders. The firing order is designed to provide for balance and to eliminate vibration to the greatest extent possible. In radial engines, the firing order must follow a special pattern since the firing impulses must follow the motion of the crank throw during its rotation. In inline engines, the firing orders may vary somewhat, yet most orders are arranged so that the firing of cylinders is evenly distributed along the crankshaft.

PURPOSE OF FIRING ORDER

These are some factors which must be considered before deciding the optimum firing order of an engine. 
• Engine vibrations
• Engine cooling 
• Development of back pressure.
• Engine balancing and
• Even flow of power.

FIRING ORDERS OF VARIOUS NUMBER OF CYLINDERS

1. 3-cylinder

Firing order
1-2-3 Saab two-stroke engine
1-3-2 BMW K75 engine

2. 4-cylinder

Firing order
• 1-3-4-2 Most straight-4s, Ford Taunus V4 engine
• 1-2-4-3 Some English Ford engines, Ford Kent engine
• 1-3-2-4 Yamaha R1 crossplane
• 1-4-3-2 Volkswagen air cooled engine

3. 5-cylinder

Firing order
• 1-2-4-5-3 Straight-5, Volvo 850, Audi 100

4. 6-cylinder

Firing order
• 1-5-3-6-2-4 Straight-6, Opel Omega A
• 1-6-5-4-3-2 GM 3800 engine
• 1-2-3-4-5-6 GM 60-Degree V6 engine
• 1-4-2-5-3-6 Mercedes-Benz M104 engine
• 1-4-5-2-3-6 Chevrolet Corvair
• 1-4-3-6-2-5 Mercedes-Benz M272 engine, Volkswagen V6’s
• 1-4-2-6-3-5 Toyota HZ engine

5. 7-cylinder

Firing order
• 1-3-5-7-2-4-6 7-cylinder single row radial engine

6. 8-cylinder

Firing order
• 1-8-4-3-6-5-7-2 1988 Chrysler Fifth Avenue, Chevrolet Small-Block engine
• 1-8-7-2-6-5-4-3 GM LS engine, Toyota UZ engine
• 1-3-7-2-6-5-4-8 Porsche 928, Ford Modular engine, 5.0 HO
• 1-5-4-8-7-2-6-3 BMW S65
• 1-6-2-5-8-3-7-4 Straight-8
• 1-8-7-3-6-5-4-2 Nissan VK engine
• 1-5-4-2-6-3-7-8 Ford Windsor engine
• 1-5-6-3-4-2-7-8 Cadillac V8 engine 368, 425, 472, 500 only
• 1-5-3-7-4-8-2-6 Ferrari Dino V8 (F355)
• 1-2-7-8-4-5-6-3 Holden V8

7. 10-cylinder

• 1-10-9-4-3-6-5-8-7-2 Dodge Viper V10 
• 1-6-5-10-2-7-3-8-4-9 BMW S85

8. 12-cylinder

Firing order
• 1-7-5-11-3-9-6-12-2-8-4-10 Ferrari 456M GT V12
• 1-7-4-10-2-8-6-12-3-9-5-11 Lamborghini Diablo VT
• 1-4-9-8-5-2-11-10-3-6-7-12 Caterpillar Inc. 3412E
• 1-12-5-8-3-10-6-7-2-11-4-9 Audi VW Bentley W12 engine
• 1,12,7,6,3,10,11,2,5,8,9,4 Rolls-Royce Merlin
• 1,12,4,9,2,11,6,7,3,10,5,8 Lamborghini Aventador

9. 16-cylinder

Firing order
1-12-8-11-7-14-5-16-4-15-3-10-6-9-2-13 Cadillac V16 engine

10. 20-cylinder

Firing order
• 1-12-8-11-7-14-5-16-4-15-3-10-6-9-13-17-19-2-18-20 Cadillac V20 engine