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. 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 cent