Redon, F., Kalebjian, C., Kessler, J., Rakovec, N. et al., "Meeting Stringent 2025 Emissions and Fuel Efficiency Regulations with an Opposed-Piston, Light-Duty Diesel Engine," SAE Technical Paper 2014-01-1187, 2014, doi:10.4271/2014-01-1187.
With current and pending regulations-including Corporate Average Fuel Economy (CAFE) 2025 and Tier 3 or LEV III-automakers are under tremendous pressure to reduce fuel consumption while meeting more stringent NOx, PM, HC and CO standards. To meet these standards, many are investing in expensive technologies-to enhance conventional, four-stroke powertrains-and in significant vehicle improvements. However, others are evaluating alternative concepts like the opposed-piston, two-stroke engine.First manufactured in the 1890s-and once widely used for ground, marine and aviation applications-the historic opposed-piston, two-stroke (OP2S) engine suffered from poor emissions and oil control. This meant that its use in on-highway applications ceased with the passage of modern emissions standards.Since then, Achates Power has enhanced the opposed-piston engine and resolved its historic challenges: wrist pin and power cylinder durability, piston and cylinder thermal management, piston ring integrity and oil consumption .An in-depth study on opposed-piston, two-stroke diesel engine performance and emissions in a light-duty truck application is presented here for the first time in a technical paper. The paper includes a: Brief review of the opposed-piston, two-stroke engine's architectural advantages (thermodynamics, pumping work and combustion)Comprehensive overview of the engine's performance and emissions results, including indicated thermal efficiency, fuel consumption and emissionsComparison of fuel economy and emissions to the published benchmark, the Cummins 2.8L ATLAS Diesel Engine Discussion of an exhaust temperature control strategy that is used to meet the aggressive catalyst light-off requirements of light-duty applications by achieving rapid catalyst light-off after a cold startComparison of engine balance of the light-duty truck concept engine and a state-of-the-art gasoline V6 engineExamination of the packaging options for an opposed-piston, two-stroke engine in a light-duty truck applicationThe results of this study show that the Achates Power opposed-piston engine benefits-high efficiency, low emissions and reduced cost, mass and complexity-already demonstrated for medium-duty commercial vehicles  are also available for light-duty applications. In fact, to an even greater extent: over 30% fuel economy improvement when compared to an equivalent four-stroke diesel engine.Moreover, this study shows that the final 2025 light-truck CAFE fuel economy regulation not only has the potential to be met but also the potential to be exceeded with a full-size 5,500 lb. pick-up truck by simply applying the Achates Power technology without any hybridization or vehicle improvements.