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With accelerating exhaust gas regulations in recent years, not only CO / HC / NOx but also PN regulation represented by Euro 6 d, China 6 are getting stricter. PN reduction by engine combustion technology development also progresses, but considering RDE, PN reduction by after treatment technology is also indispensable. To reduce PN exhausted from the gasoline engine, it is effective to equip GPF with a filter structure. Considering the installation of GPF in limited space, we developed a system that so far replaces the second TWC with GPF for the TWC 2 bed system. In order to replace the second TWC with GPF, we chose the coated GPF with filtering and TWC functions. Since the initial pressure drop and the catalyst amount (purification performance) of coated GPF have a conflicting relationship, we developed the coated GPF that can achieve both the low initial pressure drop and high purification performance.

Recently, Spark-Assisted HCCI has been developed to improve combustion robustness. On the other hand, there needs to be an aftertreatment system which can purify both stoichiometric and lean exhaust gas to meet stringent emission regulations. The difficulty of exhaust aftertreatment under lean conditions is not only NOx conversion but also HC conversion. This is because in addition to the lower exhaust gas temperature there is more paraffin in the HCCI gas. A new catalyst system which includes TWC at the close-coupled position and a lean catalyst at the underfloor position was developed. The underfloor lean catalyst has the ability of HC conversion (especially paraffin) and of NOx conversion. This concept for lean exhaust from Spark-Assisted HCCI can achieve high NOx and HC conversion efficiencies.

The reduction of NOx in exhaust gas has been a major challenge in diesel engine development. For the NOx reduction issues, a new Lean NOx Catalyst (LNC) aftertreatment system has been developed by Honda. A feature of the LNC system is the method that is used to reduce NOx through an NH₃-Selective Catalytic Reduction (NH₃-SCR). In an LNC system NOx is adsorbed at lean conditions, then converted to NH₃ at rich conditions and subsequently reduced in the next lean phase. In recent years, as the efficiency of the diesel engine has improved, the exhaust gas temperatures have been reduced gradually. Therefore, the aftertreatment system needs to be able to purify NOx at lower temperatures. The development of a new LNC which has a high activity at low temperature has been carried out. For the improvement of the LNC three material improvements were developed. The first of these was the development of a NOx adsorbent which is matching the targeted exhaust gas temperatures.

This paper describes a technology for reducing cold hydrocarbons (HCs) emissions during cold engine start-up. The technology consists of a new HC adsorption system and a method for detecting the deterioration of adsorption performance of the HC adsorber. This active type HC adsorption system is added to Honda's current SULEV system technologies (high performance catalysts, catalyst quick warm-up control, and high accuracy A/F control), for further reduction of cold HC emissions at start-up. In addition, a new sensor has been developed to detect humidity in the exhaust gas, which in turn is used to predict performance deterioration of the HC adsorber. During FTP (Federal Test Procedure) testing, this emission control system has achieved a reduction of more than 70% in cold HC emissions during cold start, and a reduction of about 60% in NMOG weighted mean (WM) value, as compared to without the HC adsorption system.