August 5, 2026 — Southwest Research Institute successfully completed development of an optimized spark-ignited hydrogen (H2) internal combustion engine (ICE) designed for medium-duty commercial vehicles. The multiyear development resulted in an H2-fueled ICE that demonstrates diesel-like torque characteristics and performance while producing near-zero tailpipe CO2 emissions.
“In addition to decades developing medium- and heavy-duty engines, SwRI has some of the most extensive experience in the world developing and testing H2-ICEs for internal research, clients and industry demonstrations,” said Dr. Qilong Lu, a program manager in SwRI’s Powertrain Systems Engineering Department and one of the leads on this project. “The engine was designed, constructed and rigorously tested at SwRI to ensure efficiency and performance.”
Over the course of two years, SwRI collaborated with a commercial client and selected Tier 1 suppliers to plan, design, and manufacture the engine. The initial program spanned both single-cylinder and multi-cylinder engine development. The engine can be installed in a commercial medium-duty truck chassis, providing enough torque and power to compete with diesel-fueled engines. It is based on a pent-roof-style engine design previously developed for gasoline combustion but optimized to burn hydrogen.
“We began at the single-cylinder level, focusing on optimizing combustion and injection strategies,” Lu said. “From there, our team ramped up efforts to develop the full multi-cylinder engine, addressing key challenges such as pre-ignition, combustion stability and overall systems integration.”
The engine’s modified port geometry improves flow and is better suited to hydrogen’s faster combustion speeds. A larger intake valve improves volumetric efficiency, and H2-specific fuel injectors contribute to the engine’s enhanced combustion. It is equipped with a turbocharger that delivers diesel-like torque performance and includes an SwRI-designed and -calibrated engine control system.
Previous SwRI-led projects include the creation of a Class 8 heavy-duty hydrogen-powered demonstration vehicle, converting a natural gas-fueled engine into an H2-ICE with minimal hardware modifications. More recently, SwRI engineers upgraded the H2-ICE with a state-of-the-art turbocharger to significantly improve performance, making it competitive with current long-haul diesel engines with a focus on fuel economy while maintaining near-zero tailpipe emissions.
“The project brought together many areas and experts at the Institute to complete,” said Chris Bitsis, assistant director of SwRI’s Powertrain Systems Engineering Department, who oversees combustion research programs. “SwRI’s hydrogen combustion engine program is working every day to advance this technology and showcase its potential as a near-zero carbon emissions industry solution.”
SwRI has a multidisciplinary team dedicated to Hydrogen Energy Research initiatives to deploy decarbonization technologies across a broad spectrum of industries. Learn more at SwRI Hydrogen Energy Research.
For more information, visit Hydrogen Powered Vehicles or contact Jesus Chavez, +1 210 522 2258, Communications Department, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238-5166.