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UEGI(Unburned Exhaust Gas Ignition) is expected to help faster warm-up of a close-coupled catalytic converter (CCC) by igniting the unburned exhaust mixture using two glow plugs installed upstream of the catalyst. In this study, a control module and an algorithm for the UEGI technology was developed. In addition, a hydrocarbon adsorber was tested with the UEGI system for more effective reduction of HC emission during the cold start. The control module changes I/O signals of the ECU, to control ignition on/off, glow plug on/off, and A/F ratios during cold start. Because the system is designed to be applicable to conventional vehicles, its repeatability, stability, and precision of control were tested and analyzed on an engine test bench and vehicle test. Experimental results show that the CCC reaches the light-off temperature faster compared with the baseline exhaust system. Therefore HC and CO emissions are reduced significantly during the cold start.

This paper shows development challenges for 6 liter heavy duty off-road diesel engines to meet the Tier4 final emission regulations with a base diesel engine compliant with Tier4 interim emission regulations. Even if an after-treatment system helps to reduce emissions, quite amount of particulate matters (PM) reduction is still necessary since a diesel particulate filter (DPF) system is supposed to be excluded in Tier4 final diesel engine. The objective of this research is to see if the base engine has a feasibility to meet Tier4 final emission regulations by a change of piston bowl geometry without DPF. Quite amount of PM can be reduced by piston bowl geometry because piston bowl geometry is a very important part that enhances air and fuel mixing process that help the combustion process.