the pully is bigger than the original or smaller i forgot...its like having your accesories all run on a shorter gear. like you know how its easier to accelarate in 1st gear rather than 2nd. its a gearing thing. some of them are lighter in weight than the original so they have less unsprung weight but thats not whats responsible for freeing up the hp n torque its the size of the pully that does it.