For example, why would a car manufacturer opt to to use a 2.0L in line six instead of a 2.0L in line four in a vehicle. Are the benefits of including more cylinders in an engine worth the added complexity?
In: Engineering
Increasing displacement increase the rotating mass which decrease the maximum speed of the engine which again reduce the power. If you make the cylinder bore larger you need a bigger piston. And there is more forces on that piston so it needs to be thicker. The piston rod also needs to be thicker to handle the increased power. This puts a lot of strain on the crankshaft which also needs to be heavier to handle the weight. But even then all that acceleration of the heavy piston and piston rod is too much and you have to limit the engine speed to prevent damage to the engine. If you instead make the cylinder taller you can keep the same piston. But now it is going twice the speed which means twice the acceleration and twice the force just to move the piston up and down. This means the piston rod needs to transfer twice as much force but making it thicker also adds force to move the piston rod so you need to add even more weight. And eventually you have the same problem of too much forces and too much weight and have to limit the engine speed to keep the forces down.
And of course engine speed times torque is power. So a lower engine speed yields lower power. This is great for an engine that needs lots of torque like a truck engine or tractor engine. But when you need power to go fast you need the engine to go fast which means less displacement per cylinder.
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