Achates near-zero heavy-duty opposed-piston diesel enters fleet service; compliant with 2027 NOx levels

Achates Power announced that the 10.6-liter, heavy-duty opposed-piston, three-cylinder diesel engine it developed in a project funded by the California Air Resources Board (CARB) and several partners (earlier post) has entered fleet service with WALMART Corporation in a Peterbilt 579 tractor. It is the only diesel engine operating on the road capable of meeting CARB’s 2027 regulation, which requires a 90% reduction in emissions of NOx compared to current standards.


The 10.6-liter engine. The three cylinders are in-line, with the opposed pistons moving vertically.

The project team also demonstrated that the engine reduces carbon dioxide by 10%. The Achates Power ultra-low-NOx engine is engineered to achieve superior fuel efficiency because of its lower heat losses, improved combustion and reduced pumping losses.

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This article originally appeared in Green Car Congress, April 7, 2022