A method for initiating cavitation within the fluid within a cavitation chamber is provided. The illumination period allows the image reading device to determine a proper exposure for imaged indicia by sectioning a single frame into individual exposures. After cylinder reactivation, the given cylinder can thereafter be deactivated only after the temperature of the components has been restored to a nominal operating temperature, for example, as inferred from a second measure, representing the heat generated within the given cylinder subsequent to cylinder reactivation, determined based upon engine mass air flow or fuel flow. When the first-stage judgment step is matched, a second-stage judgment step is performed. The following conditional expressions are satisfied;1.