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
a big part of developing an engine is the design of the combustion chamber, such as how wide(bore) deep(stroke), piston speed, and compression ratio affects how it performs and behave. there are margins you can play with to try to squeeze more power but any dramatic changes in displacement will need to redesign the whole combustion chamber where as copy and pasting extra cylinders of an existing design is much more straight forward and easier. for example a lot of V-8 engines in the 80’s 90’s had to 2 ECU, each controlling 4 cylinders on either side essentially two 4 cylinder engines merged together.
so for your example of 2L 6cylinder vs 4cylinder, the combustion chamber of the 6cylinder is 0.33L ea/cylinder and the 4cylinder is 0.50L ea/cylinder. what this means for the 6cylinder is that it will generally have a smaller bore and stroke, which means it can rev to a higher RPM than the 4 cylinder with the same piston speed. higher engine RPM will generally produce more power, which some manufacturer might find worth the extra cost of developing for something like a sports car which commands a higher premium.
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