Inline 4-cylinder engine

It may be the most widely used engine with stable operation, low cost, simple structure, compact size, etc. Of course, its shortcomings are that the size is basically fixed and cannot adapt to excessive displacement, but this does not prevent it from almost occupying most of the common civilian models fact.

Horizontally opposed 4-cylinder engine

Unlike in-line or V-type engines, the pistons of horizontally opposed engines move left and right in the horizontal direction, which reduces the overall height of the engine, shortens the length, and lowers the center of gravity of the vehicle. However, there are disadvantages of higher production costs and higher maintenance costs.