Sunday, April 20 2014 @ 10:42 AM ICT
Contributed by: news
First, each cylinder in a four-stroke engine can be fired in one of two ways, depending on which downward stroke of the 720-degree cycle is used as the intake stroke that begins the cycle for that cylinder. In any engine with a given configuration, this gives the number of possible firing order as 2n, where n is the number of cylinders.
As you found, this gives eight combinations for a three-cylinder engine with evenly spaced crank throws. However, half of those combinations are duplicates with the entire order 360 degrees - one full revolution - out of phase.