The sequence or order in which the firing takes place in different engine cylinders of a multi-cylinder engine is called the firing order. In the spark-ignition engine, the high tension leads from the distributor are connected to the spark plugs at the different cylinders according to the firing order.
Requirements Of Proper Firing Order
A proper firing order reduces engine vibrations, maintains engine balancing and secures an even flow of power. The firing order differs from engine to engine. Probable firing orders, for different engines, are as follows:
|3 -cylinder engine||1-2-3|
|4-cylinder in-line engine||1-3-4-2 1-2-4-3|
|4-cylinder horizontal opposed engine (Volkswagon engine)||1-4-3-2|
|6-cylinder in-line engine(cranks in 3 pairs)||1-5-3-6-2-4 1-4-2-6-3-5 1-3-2-6-4-5 1-2-4-6-5-3|
|8-cylinder in-line engine||1- 5-3- 6-2-4-7-8 1-4-7-3-8-5-2-6|
|8-cylinder V-type engine||1- 5-4-8-6-3-7-2 1-5-4-2-6-3-7-8 1-6-2-5-8-3-7-4 1-8-4-3-6-5-7- 2 1-8-7-3-6 -5-4-2|
Cylinder No. 1 is taken from the front of the in-line engines whereas, in V-type engines, it is taken from the front on the right side bank.
Watch the video below to understand all about engine Firing Order.
Even and Uneven firing order
Firing order affects the balance, vibration, noise, smoothness, cooling, and sound of the engine. Evenly spaced firing order (also called even firing order) means that the angle between each firing is equal. In four-stroke engines require a firing interval of 720 divided by the number of cylinders.
The engines with unevenly spaced firing order not all the angles between firings are equal, for example, a 6-cylinder engine with unevenly spaced firing order can have a combination of 90 and 150° firing intervals compared to a six-cylinder engine with even firing order which must have 720° /6 120 firings.
Engines that are even-firing will sound more steady and smooth, while engines that are odd, or uneven firing will have a throaty, growling sound in the engine and, depending on the design of crankshaft will often have more vibrations because of the unevenness of power delivery. Most racing car engines such as those in Formula One often have even firing intervals in all or the most part (e.g. within each bank of a V-engine) of their firing order, mostly for easier packaging of performance exhaust systems.
Engines that employ some variation on the Big-bang fire, they will have an uneven firing order because the torque variations arising from the second-order kinetic imbalance of an inline four-cylinder engine have the worst effect on rear wheel traction than uneven power output as RPM increases.
Examples of Odd-firing engines are:
- Harley-Davidson Evolution engines.
- Most 4-stroke V-Twins.
- 1986-Honda VFR 750/800.
- 2009-2014 Yamaha YZF-R1.
- Audi V10 FSI as in the Audi R8 V10.
- 2nd / 3rd generation Lamborghini Gallardo.
- Viper V10.
- Yamaha V-Max and VMAX.
- Buick 231 Odd-Fire V6.
Examples of Even-firing engines are:
- Honda NSR500V and most 2-stroke V-Twins.
- Most current production inline 4-cylinder engine.
- Most current production V6s.
- Lotus Esprit V8.
- Porsche 918 Spyder.
- McLaren M838T engine.
- Audi V10.
- 1st generation Lamborghini Gallardo.
- Toyota LR engine.