Firing Order Definition:
The order in which various cylinders of a multi-cylinder engine fire is called the firing order.
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.
1. It is desirable to have the power impulses equally spaced and from the point of view of balancing.
2. If all cylinders fired at once, power distribution would be very jerky, so the engine is set up to have the cylinders firing in sequence for a smoother power delivery.
3. If the pistons move in a certain rhythm, then they have to receive their sparks in a certain rhythm too, due to this engine will run smoothly.
(iii) decreased backpressure.
Purpose of Firing Order
These are some factors that 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.
How to determine the firing order of engine
Firing Order is Determined by the Number of Cylinders contained within that engine & Crankshaft Alignment/Offset of each Crank-Journal, during the Design/Manufacturing Process.
The firing order is determined when the engine is DESIGNED, so as to make it run as efficiently and as smoothly as possible. he forces and loads exerted by pistons on the crankshaft are calculated. The required counterweight is calculated. Plugging all these into the dynamic balancing equations, the firing order is determined such that, minimal vibrations are produced.
Designing Parameters of Firing Order :
- Number of Cylinders,
- Torsional vibrations,
- Heat distribution,
- arrangement of cylinders,
- Crankshaft Alignment/Offset of each
- Crank-Journal.
Firing order of Different types of Cylinders engine
1. Firing Order For 3 cylinder engine
Firing order
1-2-3 Saab two-stroke engine
1-3-2 BMW K75 engine
2. Firing Order For 4 cylinder engine
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
Why 1-3-4-2 firing order is preferred than the 1-2-3-4 in 4 cylinder engines?
The firing order must be considered on the basis of engine vibrations and engine cooling. Also the firing order affects the balancing of the engine.
Reasons for preferring 1-3-4-2 than the 1-2-3-4 in 4 cylinder engine:
1. The power impulses are evenly distributed and are 180 degrees apart. Therefore the firing order for the engine is 1-3-4-
2. This balance load on two bearings would be further reducing the engine vibrations.
3. It is required to cool the portion of the engine by changing the sequence. So that problem of overheating can be mitigated.
4. To provide sufficient travel time to exhaust gases. So that development of high back pressure would be avoided.
3. Firing Order For 5 cylinder engine
Firing order
• 1-2-4-5-3 Straight-5, Volvo 850, Audi 100
4. Firing Order For 6 cylinder engine
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. Firing Order For 7 cylinder engine
Firing order
• 1-3-5-7-2-4-6 7-cylinder single-row radial engine
6. Firing Order For 8 cylinder engine
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. Firing Order For 10 cylinder engine
• 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. Firing Order For 12 cylinder Engine
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.
Advantages of Firing order
(a) A proper firing order reduces engine vibrations
(b) Maintains engine balancing.
(c) Secures an even flow of power.
