The boxer internal combustion engine "evolved" from the V-shaped one and became its kind of technological improvement, just as the V-shaped engine, in turn, became a continuation of the inline one.
The beginning of a kind of career of an opposed power plant can be considered the 30s of our century. Then Volkswagen engineers began to carry out developments related to the modernization of both in-line and V-shaped engines. As a result of one of the experiments, the engineers spread two rows of pistons of the V-shaped engine 180 degrees, obtaining a new type of internal combustion engine. The main difference and peculiarity of the "opposed" is the arrangement of its pistons opposite to each other in the horizontal plane.
In such an engine, I install 4 camshafts, 2 on each side, and the gas distribution mechanism is located vertically here. This design of the engine made it possible to solve the main problem of V-shaped motors - imbalance and, as a result, vibration, causing discomfort while driving. The first production car produced with a boxer engine was the Volkswagen Beetle, and since the 60s, Subaru has relied heavily on such engines.
The opposed arrangement of the cylinders of such an internal combustion engine has many advantages: firstly, the low center of gravity of the car, which significantly affected the stability of the cars when cornering. Due to the specifics of the arrangement of the pistons, the engine is, as it were, "flattened" in the engine compartment, which reduces the roll of the car. Secondly, the engine got a good balanced performance due to the pistons working from each other, which are counterweight, creating the necessary balance. According to experts, only the inline “six” is better balanced than the “oppositor”. Thirdly, the boxer engine has a very long service life, some manufacturers give a guarantee for several hundred thousand mileage. In my opinion, there is only one drawback - because of the design features, the "boxer" is very expensive to maintain, which is only the replacement of candles! And the production of the engine is very expensive, which later affects the price tag.