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In order to reduce diesel NOx emissions, aftertreatment methods including LNT (Lean NOx Trap) and urea SCR (Selective Catalytic Reduction) have been researched. One of the shortcomings of urea SCR is its NOx reduction performance degradation at low exhaust gas temperatures and possible emission of unregulated byproducts. Here, a new type of a urea-dosing device to overcome these shortcomings is studied. This dosing device actively produces ammonia without depending upon the exhaust gas temperature, and designed for onboard application. The device incorporates an electrically heated bypass with a hydrolysis catalyst. An injector supplies urea solution into the bypass. The bypass is heated only when thermolysis is needed to produce ammonia (NH3). The hydrolysis catalyst further assists in the production of NH3. The ammonia gas obtained is then mixed with the main exhaust gas flow.

A new catalyzed hydrocarbon (HC) trap control system has been developed to reduce HC emission at cold engine start. The HC trap function changes according to its temperature, so it is important to optimize its temperature profile. To realize the best profile, the engine system was optimized with a thin wall exhaust tube, a thin wall HC trap and a new engine control, which controls ignition timing without engine stability deterioration. In a LA-4 mode test with some trial HC traps, the results showed good performance which met ULEV/SULEV standard.