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Turbo hydrogen engine nears power, efficiency of diesel

Southwest Research Institute (SwRI) has upgraded its hydrogen-powered heavy-duty internal combustion engine (H₂-ICE) concept with a state-of-the-art turbocharger. The upgrades have significantly improved performance across the board, making the engine competitive with current long-haul diesel engines focused on fuel economy while maintaining near-zero tailpipe emissions.

In 2023, SwRI converted a traditional natural gas-fueled internal combustion engine to run solely on hydrogen fuel with minimal modifications. It was integrated into a Class-8 truck as part of the institute's H₂-ICE project to demonstrate a cost-efficient hydrogen-fueled engine as an option for zero-tailpipe carbon dioxide heavy-duty transportation.

The new turbocharger unit increases the truck's already solid performance by increasing peak torque from 1,494 to 1,760 lb-ft and peak power from 370 to 440 hp. Modern long-haul heavy-duty engines range from 1,450 to 1,850 lb-ft and range between 400 to 500 hp.

"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."

Hydrogen engines often struggle to maintain the airflow necessary during fast acceleration to eliminate preignition and minimize NOx emissions. SwRI addressed this challenge by working with a commercial supplier that engineered the new turbocharger to SwRI's specifications. The turbocharger shaft is mechanically linked to the crankshaft through a variable drive, allowing it to provide the necessary boost pressure on demand.

"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. "We are excited to continue pushing this technology forward for a sustainable future."

The Class-8 demonstration vehicle was developed as part of SwRI's Hydrogen Internal Combustion Engine (H₂-ICE) consortium. SwRI continues helping the automotive and transportation industries understand and address technical challenges in developing clean and efficient hydrogen vehicles. The consortium's completed Class-8 H₂-ICE demonstration vehicle offers the long-haul trucking market another zero-greenhouse gas option. Learn more at H₂-ICE.

"The U.S. has the engine factories and supply chains necessary to put this technology into production today," said Daniel Stewart, vice president of SwRI's Powertrain Engineering Division.

Source: Southwest Research Institute

Published November 2025

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