Abstract: Kantor proposed a spark ignition engine model to predict engine cyclic variation in terms of some assumptions. In this paper a modified Kantor model is proposed.We show that exhaust blowdown process and variable exhaust residual gas mass fraction, neglected in the Kantor model, significantly reduce cyclic variability. However, prior-cycle unburned fuel not considered in the Kantor model apparently aggravates cyclic variability of next cycle. These three factors interact each other and result in abatement and even disappearance of cyclic variation. No significant cyclic variability is predicted for realistic ranges of these parameters. Only for extremely unrealistic ranges of model parameters cyclic variation reluctantly shows up. Moreover, even using the Kantor model, cyclic variability is predicted only for rather extreme, somewhat contrived choices of the model parameters.