Next-generation hydrogen truck engine achieves major gains in efficiency and power

by Clarence Oxford
Los Angeles CA (SPX) Nov 18, 2025

Southwest Research Institute (SwRI) has developed a hydrogen-fueled internal combustion engine for heavy-duty trucks, upgrading it with a high-performance turbocharger. This enhancement increases the engine's peak torque from 1,494 to 1,760-foot pounds and boosts peak power from 370 to 440 horsepower, matching the outputs of current diesel engines used in long-haul trucking.

Originally converted in 2023 from a natural gas engine to run exclusively on hydrogen, the engine was fitted into a Class 8 truck for the H2-ICE demonstration project. The newest turbocharger improves airflow, which increases torque, horsepower, and the engine's peak efficiency to 44.0 percent - a leading value for spark-ignited engines. The modifications allow the hydrogen engine to operate alongside diesel models focused on fuel economy, while delivering near-zero tailpipe emissions.

"Upgrading this driven turbocharger gave us the airflow needed to continue improving the engine's performance," said Chris Bitsis, assistant director of SwRI's Powertrain Systems Engineering Department, who oversees combustion research programs. "For instance, in addition to the torque and horsepower gains, the engine's peak efficiency has also improved to 44.0%, which is class-leading for a spark-ignited engine. The torque and power ratings are comparable with diesel trucks focused on fuel economy currently on the road with the bonus of near-zero tailpipe emissions."

Maintaining airflow during rapid acceleration is a challenge for hydrogen engines, especially for eliminating preignition and reducing NOX emissions. To address this, SwRI collaborated with a commercial supplier to design the new turbocharger linked mechanically to the crankshaft via a variable drive, enabling on-demand boost pressure.

"This is a significant milestone in the history of SwRI's hydrogen combustion engine program and provides further evidence of the technology's readiness," Bitsis said.

The vehicle was built as part of SwRI's Hydrogen Internal Combustion Engine (H2-ICE) consortium. The completed Class 8 truck shows that hydrogen-fueled engines offer viable zero-greenhouse gas options for the trucking industry.

"I am proud of our team at SwRI for demonstrating that there is a high efficiency, zero-emission transportation solution available to help reduce CO2 and criteria pollutants," said Daniel Stewart, Vice President of SwRI's Powertrain Engineering Division. "The U.S. has the engine factories and supply chains necessary to put this technology into production today."