of 1-5-3-6-2-4, which results in perfect primary and secondary balance. However, a firing order of 1-2-4-6-5-3 is common on medium-speed marine engines. V6 engines with an angle of 90 degrees between the cylinder banks have used a firing orders of R1-L2-R2-L3-L1-R3 or R1-L3-R3-L2-R2-L1. Several V6 engines with an angle of 60 degrees have used a firing order of R1-L1-R2-L2-R3-L3. Flat-six engines have used firing orders of R1-L2-R3-L1-R2-L3 or R1-L3-R2-L1-R3-L2. V8 engines use various different firing orders, even using different firing orders between engines from the same manufacturer. V10 engines used firing orders of either R1-L5-R5-L2-R2-L3-R3-L4-R4-L1 or R1-L1-R5-L5-R2-L2-R3-L3-R4-L4. V12 engines use various different firing orders. In a radial engine, there are always an odd number of cylinders in each bank, as this allows for a constant alternate cylinder firing order: for example, with a single bank of 7 cylinders, the order would be 1-3-5-7-2-4-6. Moreover, unless there is an odd number of cylinders, the ring cam around the nose of the engine would be unable to provide the inlet valve open - exhaust valve open sequence required by the four-stroke cycle. Firing interval To minimise vibrations, most engines use an evenly spaced firing interval. This means that the timing of the power stroke is evenly spaced between cylinders. For a four-stroke engine, this requires a firing interval of 720° divided by the number of cylinders, for example a six-cylinder engine would have a firing interval of 120°. On the other hand, a six-cylinder engine with an uneven firing interval could have intervals of 90° and 150°. Engines with an even firing interval will sound smoother, have less vibration and provide more even pressure pulses in the exhaust gas to the turbocharger. Engines with an uneven firing interval usually have a burble or a throaty, growling engine sound and more vibrations. The main application of uneven firing intervals is motorcycle engines, such as big-bang firing order engines. Examples of odd-firing engines are most four-stroke V-twin engines, 1961-1977 Buick V6 engine, 1985-present Yamaha VMAX, 1986–present Honda VFR 750/800, 1992-2017 Dodge Viper V10, 2008-present Audi/Lamborghini 5.2 V10 40v FSI, Aston Martin 5.9 V12 1999-2018 and the 2009-2020 Yamaha R1 (inline four engine with a crossplane crankshaft). See also Engine configuration Four-stroke engine Two-stroke engine References Engine technology