What Causes Piston Slap?

According to Dr. Victor Wong of the Massachusetts Institute of Technology, piston slap is one of the most confounding problems of the internal combustion engine. When the piston moves up and down within a cylinder, it moves side to side as well. This movement wastes fuel and causes engine damage as well as the tell-tale banging sound.

MIT researchers have determined through the use of a computer model that more efficient engine designs can reduce the piston slap problem. Through this model, researchers were able to see the path of each piston's movement within the cylinder, the force that it hits the cylinder wall and how the piston changes after impact.