• Name comes from back-and-forth (reciprocating) motion of pistons
• “Recip” Engines convert energy by combusting fuel and air in a tight space, which creates pressure to move pistons back-and-forth
• Back-and-forth motion converts to rotating motion by connecting pistons to Engine Crankshaft with Connecting rods
• By-product of combustion occurring due to back-and-forth movement and rotation movement is Friction
• Friction causes – Additional heating – Excessive wear – Loss of engine efficiency