Inliners International Forums General Discussion Engines GM 4 cylinders 151 153 181

Thanks Panic, I'm having a hard time getting my head around this part.

"The reason for the piston's higher speed during the 180° rotation from mid-stroke through top-dead-centre, and back to mid-stroke, is that the minor contribution to the piston's up/down movement from the connecting rod's change of angle here has the same direction as the major contribution to the piston's up/down movement from the up/down movement of the crank pin. By contrast, during the 180° rotation from mid-stroke through bottom-dead-centre and back to mid-stroke, the minor contribution to the piston's up/down movement from the connecting rod's change of angle has the opposite direction of the major contribution to the piston's up/down movement from the up/down movement of the crank pin."
I see how the piston speed would vary at different degrees of crank rotation, but I really don't get why the piston would move faster in the top 180 than in the bottom 180. It is what it is whether I understand it or not.