The Significance of High Value of Ignition Retard Control on the Catalyst Lightoff

Ever stringent emission legislation has called for more advanced measures for petrol engine emission control. The main chanllenge is to largely cut off the engine cold-start emissions. The problem is that the catalytic converter does not operate effectively at temperature below the range of 250 - 300 °C at engine cold start. This paper presents an alternative approach, which needs no assistance from the external heat source such as electrically heating or burner/afterburner-assisting, etc, for rapid light-off an automotive catalyst using high value of ignition retard control. Proper control strategies permit a catalyst to reach lightoff within 50 seconds from cold-start. Emission data of unburnt hydrocarbons (in terms of hexane-equivalence) and carbon monoxide at both the upstream and downstream of a catalytic converter are measured. Results show that significant reduction in emissions can be achieved with proper ignition control strategies. The effect of high value ignition retard on the cold-start NOx emission is also briefly discussed.