Generalized cold start emissions reduction strategy

A system providing an approach for catalytic converter warmup mode is applicable to multiple vehicle applications including hybrid vehicles. The system determines exhaust enthalpy during conditions including transient engine speed and transient engine load for a catalytic converter receiving exhaust output from an engine. Multiple exhaust parameter measurement devices each measure exhaust conditions entering the catalytic converter. A processor receives output from each of the exhaust parameter measurement devices and continuously calculates an enthalpy of the catalytic converter. The calculated enthalpy of the catalytic converter is repeatedly compared to a predetermined enthalpy threshold required to achieve catalytic light-off saved in a memory.