PSI’s new 8.8-liter ultra-low nitrogen oxide (NOx) emission propane engine was recently certified by the U.S. Environmental Protection Agency (EPA) and California Air Resources Board (CARB).

Produced in collaboration with Navistar’s IC Bus brand, the engine is certified to a NOx emission standard of 0.02 grams per brake horsepower (g/bhp-hr), making it one of the cleanest propane engines available on the transportation market. The 8.8-liter engine is certified beyond the EPA’s strictest emission standards and also exceeds the California Air Resource Board (CARB)’s optional low NOx standard for heavy-duty engines.

In addition to having an industry leading NOx emission standard, the engine’s carbon dioxide (CO2) emission rate is 10 percent better than that of current competitive propane engines. School bus fleets making the switch from diesel to propane engines are eligible to receive federal, state and private grants.

“PSI is proud to support the growth of our customer IC Bus, which first introduced the 8.8-liter propane engine in 2015,” PSI CEO John Miller says. “We continue to make advancements to our 8.8-liter engine, which is clean burning and unmatched in power and performance in the transportation industry.”

The new engine offers 270 horsepower with 565 lb-ft of torque, comparable to PSI’s existing propane engines. The company will continue to offer its conventional 8.8-liter propane engine as well as the new ultra-low NOx version. The ultra-low NOx engine will power IC school buses. Production is anticipated early next year.

The ultra-low NOx 8.8-liter engine reaffirms PSI’s commitment to producing clean-running high performance power systems for the transportation industry. For the past few years, PSI and IC Bus have worked together on propane and gasoline-powered alternatives to diesel school buses in an effort to reduce NOx emissions. NOx emissions are known to be harmful to humans and the environment and contribute to ozone, smog and other air quality issues.

“IC Bus is proud to once again collaborate with PSI to bring a clean, powerful, high quality alternative fuel engine to the school bus industry,” said Trish Reed, vice president and general manager, IC Bus.