What is a flat four? What is a boxer engine? This video will explain the benefits of a flat engine, specifically a flat four engine with horizontally opposed pistons./Engineering Explained
The main advantages of a boxer engine are the primary and secondary engine balance, and the very low center of gravity compared to other engines. H4 engines are one of the best engine designs, however they are more costly than the inline counterpart.
The biggest advantage of the boxer engine is the low profile, which keeps the center of gravity low and thus reduces the amount of load transfer you have in the car during braking, cornering, or accelerating, which improves grip.
With a lower center of gravity, you can also reduce body roll and choose to use softer springs. Additionally, in the event of a collision, it’s easier to position the engine so that it goes underneath the passenger compartment, rather than into the passenger compartment, for improved safety./Engineering Explained