Why would engine designers opt to include more cylinders in an engine instead of increasing the displacement?

Question

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

Answer 1

The larger an individual combustion chamber is, the slower it will completely burn. Also a more uneven, incomplete combustion. More and smaller combustion chambers are more efficient.

However, the same power output from less displacement means higher rpm and thus lighter and better lubricated components, tighter tolerances, less margin of production error.

Hence, old engines were big, rough and slow… modern engines are smaller, but more delicate.