Abstract
Spark timing retard during cold starting and cold idle is very useful technology for raw THC reduction. High cell density with thin wall catalyst is another main technology for after treatment of emission. The other challenge-able subject for vehicle emission is to meet emission regulation with low cost. It is studied to use CCC only exhaust system for SULEV. For CCC only system, compact exhaust manifold was designed to make enough space for catalyst, to reduce catalyst light off time and to make afford to reduce precious metal. According to computer simulation result, even with compact exhaust manifold, flow distribution and O2 sensing were better than base exhaust manifold. Comparison with base exhaust system (CCC + UCC), NMHC is reduced about 30% with CCC only exhaust system that has 50% of precious metal of base exhaust system. On the other hand Nox and CO emissions were increased. However Nox and CO emissions are much dependent from AFR control. Therefore Nox or CO emissions can be reduced by using gap between catalysts and finding proper position of rear O2 sensor.