This calculator computes the motion data of a piston in a cylinder from TDC to BDC. Various parameters may be selected from the provided Pontiac engine examples or you may enter your own. Piston Travel is inches down from TDC. Piston Speed is in Feet per Minute (FPM), Effect C.R. is the effective compression ratio. Effect Lever is the effective lever arm in inches. Its maxiumum value is half of stroke which occurs at the optimum crank angle.