In this study, an exhaust system compliant with future regulations was developed for a non-road 110PS engine with a Tier-4f aftertreatment system, and the emission characteristics of the engine were investigated in the non-road transient mode (NRTC). For the system to comply with future exhaust regulations, a DPF was installed, and an electrical heated catalyst (EHC) device was installed to manage exhaust gas temperature. The emission characteristics of exhaust gas were examined according to the power and applied duration of EHC, and the effects of catalyst coating and the urea water solution (UWS) injection map on NOx reduction, NH₃ slip, and N₂O emissions in NRTC mode were investigated. The application of a 4 kW class EHC system enables the lowering of the injection starting temperature of the UWS, as reliable gas heating (heating duration control) is guaranteed. When the injection starting temperature (based on the SCR inlet temperature) was set to 150 °C, NSR map, (III) in conjunction with the operation of the EHC, effectively achieved significant NOx reduction in NRTC mode without deposit and wetting occurring in the mixer and exhaust pipe. Regarding changes in EHC power from 3 kW to 4 kW, it was observed that a NOx reduction of 0.05 g/kWh occurs in the cold NRTC mode, but in the hot NRTC mode, it was found that the relative decrease in the UWS is due to the increased NO₂ conversion efficiency as a result of the oxidation catalyst, making 3 kW more advantageous. Furthermore, due to the increase in NO₂ concentration caused by the oxidation catalyst and the increase in the low-temperature injected UWS, NH₄NO₃ was formed, which resulted in an increase in PM emissions and a significant increase in N₂O emissions around an exhaust temperature of 250 °C. When the EHC power was set to 3 kW and the volume of oxidation catalyst and the amount of UWS injection were adjusted, applying EHC in the NRTC mode resulted in an additional NOx reduction of 58.6% and 88.4% in cold and hot modes, respectively, compared with not using EHC, with a fuel penalty of approximately 1.67%, while limiting the peak concentrations of N₂O and NH₃.

All vehicles available for sale undergo certification tests mandated by law, and their certified fuel efficiency from these tests is indicated and disclosed. However, to address discrepancies between the certified fuel efficiency and actual driving conditions, more sophisticated certified modes, post-certification systems, and real-world driving tests have been introduced to complement the fuel efficiency certification system. The incorporation of a real-world driving mode, similar to certification modes, in vehicle research and development is of paramount importance from a directional perspective. To achieve this, various methods of configuring real-world driving modes have been proposed and applied in research. However, the validation of the correlation between fuel efficiency in real-world driving modes and certified driving modes is relatively limited. This study aimed to construct real-road driving cycles that are similar to the federal test procedure (FTP-75) and highway fuel economy test (HWFET) certification modes to determine the differences between the driving characteristics of the certification modes and real-road driving. The present study employed the commonly used relative positive acceleration analysis method along with a segmented short-trip technique for analysis. Additionally, variables such as fuel consumption and driving time were utilized to diversify our analytical methods. Test Routes A and B were configured for comparison with the fuel efficiency certification mode. An analysis of the relative positive acceleration (RPA) in both the test routes and certification mode confirmed that Test Route B, reflecting the actual driving patterns, closely follows the RPA distribution of the certification mode. Additionally, the fuel consumption for each short trip on each route was graphically represented, addressing aspects where determining the driving characteristics based solely on the RPA, such as the road grade, was difficult.