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Study Shows Heavy-Duty Near-Zero-NOx Engine Significantly Cuts Pollution

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Kent Johnson, CE-CERT associate research engineer

September 10, 2018

A recent study demonstrated the ability of near-zero-NOx heavy-duty truck engines to reduce air pollution significantly.

In simulated on-road testing, the new 11.9-liter Cummins Westport near-zero-NOx natural gas engine achieved California’s optional low-NOx standard of 0.02 grams per brake horsepower, and maintained those emissions levels during all types of driving. The University of California, Riverside, College of Engineering Center for Environmental Research and Technology (CE-CERT) led the tests. The CEC, SoCalGas, and South Coast AQMD funded the research.

The evaluation of the engine included regulated and nonregulated emissions, ultrafine particles, global warming potential, and fuel economy. CE-CERT performed the study with in-use testing that simulated various types of driving conditions, from pulling a heavy-duty truck into a loading dock to regional hauling. The group performed similar tests on the equivalent 8.9-liter near-zero natural gas engine last year, and reported that the smaller engine had even lower emissions.

“The first study was a smaller engine intended for use in school buses and trash trucks, which are only about 30 percent of the heavy-duty inventory. The new engine is for drayage and movement of goods, or 70 percent of the inventory,” said Kent Johnson, associate research engineer at CE-CERT, who led the tests.

“The transportation sector accounts for more than 80 percent of smog-forming emissions in California,” said Sharon Tomkins, vice president of customer solutions and strategy for SoCalGas. “The test results from UC Riverside once again show that the latest natural gas engine technology, which is available and on the road today, will play a vital role in achieving California’s clean air goals.”

Photo ©Westport Innovations, used by permission

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