Pathways Towards Low CO2 and NOX Emissions – Demonstration of a Heavy-Duty Hybrid Powertrain

Authors

C. Bitsis, S. Patil, E. Smith, T. Briggs, S. Patil, Southwest Research Institute, San Antonio, USA

Year

2025

Print Info

Production/Publication ÖVK

Summary

Meeting the upcoming United States NO_X and CO₂ regulations for 2027 requires new approaches for powertrain technology. Previous reporting from Southwest Research Institute has shown one pathway towards compliance using hydrogen fuel with strong air/fuel ratio control and state of the art aftertreatment technology. For applications which are likely to remain liquid fueled, other technology approaches are required. A demonstration of such an approach was made to enable a diesel engine to meet these coming regulations. In this demonstration for a Class-8 vocational truck, a 13-L diesel engine was replaced with a 6.8-L engine equipped with cylinder deactivation (CDA) and a 305 hp e-motor in the P2 configuration, yielding a total powertrain output of 490 hp. This powertrain was complemented by a copper zeolite SCR-based aftertreatment system using a 48 V electric heater for thermal management. The combination of CDA and electric heating yielded tailpipe NO_X emissions well below the EPA 2027 standards. The strong downsizing and e-motor yielded powertrain CO₂ emissions of 455 g/bhp-hr on the FTP cycle. This offers estimated vehicle-level CO₂ emissions of 150-160 g/ton-mi, which can satisfy the 2030-31 EPA Phase 3 Greenhouse Gas standard for vocational trucks. This demonstration shows a solution for retaining diesel-fueled vehicles as part of the decarbonized future of mobility in applications where electric or hydrogen-based powertrains are not suitable.

ISBN

978-3-9504969-4-9

DOI

https://doi.org/10.62626/681s-x4f7 Copy link

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