ACT Expo 2024: Achates OP engine shows up to 20% efficiency gain

On display at ACT Expo in Las Vegas this week is what Achates Power, Inc. (API) described as the cleanest and most efficient internal combustion engine (ICE) architecture demonstrated to date.

Achates Power opposed piston engine architecture Achates Power opposed piston engine architecture. (Photo: Achates Power)

API said it has demonstrated the opposed-piston (OP) architecture is capable of using today’s aftertreatment systems to meet future ultra-low NOx emissions standards with compliance through the 800,000-mile useful life requirements. It also offers low-load, idle and off-cycle emissions capability.

In a joint demonstration with CALSTART and Walmart, an API 10.6 L engine was retrofitted into a production Class 8 truck to meet the proposed 2027 ultra-low NOx emissions standard and with an off-the-shelf current production one-box aftertreatment system, Achates noted. The company reported testing in California achieved up to 10.8 mpg on a 389-mile delivery route averaging 10% better fuel economy than baseline, with the advantage increasing to 22% on some routes.

In February at Argonne National Laboratory, the Department of Energy also began testing an API engine utilizing hydrogen combustion with compression ignition. In addition, joint testing with renewable diesel producer Neste was able to boost the OP engine’s 10% greenhouse gas emissions (GHG) reduction by an additional 4% to 5% when using R99 compared to fossil diesel across all test cycles - the lowest GHG level API measured to-date, the company said.

Walmart putting Achates low-emissions engine to the test Walmart recently took delivery of a Peterbilt 579 with an Achates 10.6 L, three-cylinder opposed piston engine

“For the first time, an ICE architecture has been simultaneously proven to reduce NOx, beat the most stringent regulations proposed with margin to spare and improve real-world fuel economy by as much as 20%, while demonstrating extended life compliance,” said Dave Crompton, CEO of API.

“API has demonstrated that its technology can be put into practical use without the added complexity, cost and reliability concerns associated with stretching conventional engines and emission systems to meet the future low NOx and CO2 limits, and without the need for a fleet to redesign routes around shorter-range vehicles and sparse refueling/recharging infrastructure,” said Dr. John Wall, Board of Directors, API and former Cummins CTO. “For fleets that ultimately want to reach zero net-carbon emissions, including renewable diesel and hydrogen, the Achates technology is a good match.”

Other benefits of the API engines include lower heat rejection, higher power density and fewer moving parts for better reliability and increased fuel efficiency, Achates said. Every stroke is a power stroke, which company said delivers optimal thermal efficiency – a key concern for fleets for 2027 and beyond emissions regulations where thermal management impacts aftertreatment cost, simplicity and functionality.

The OP architecture can be manufactured through sustainable assembly practices and with approximately 300 fewer parts compared to today’s four-stroke engines, said Achates. It added that materials can be efficiently procured through today’s supply chain, minimizing the risk of sourcing disruptions and supply constraints.


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