System for Increasing Exhaust Gas Temperature for Catalyst Activation at Light Load Condition in Diesel Engines

Although in-cylinder combustion improvements have steadily led to reduced exhaust emissions in diesel engines, effective after treatment technology is increasingly important for meeting future extremely low emissions targets. Oxidation catalysts have already been fitted to some passenger cars and trucks. However, at low load operation the exhaust gas temperature is only about 373 K, too low for catalyst activation. In this study, to increase catalyst activation at low load, throttling of intake and exhaust gas flow, cylinder deactivation, and exhaust cam profile modifications were investigated for increasing the exhaust gas temperature. With an optimized combination of these methods, the exhaust gas temperature could be increased to above 573 K and achieve catalyst activation even for idling conditions.