The plastic cover of a Subaru Boxer engine showing the Subaru constellation logo - Topuria Design/Shutterstock Flat engines are horizontally-opposed piston engines, and this group includes Boxer ...

View post: Honda Just Gave the Civic Hybrid a “Fake Manual” Mode Boxer engines feature flat, opposing pistons that move in opposite directions for smooth operation. Subaru and Porsche are primary ...

Flat engines are horizontally-opposed piston engines, and this group includes Boxer engines, but not opposed-piston engines like the Cummins 14.3L Advanced Combat Engine (ACE) designed to power tanks.