Achates Power
| Company type | Private |
|---|---|
| Industry | Engine manufacturing |
| Founded | 2004 |
| Founder | James U Lemke |
| Headquarters | San Diego , United States |
Area served | Commercial and passenger vehicles, defense sector |
Key people | James U Lemke (Founder) |
| Products | Opposed-piston, two-stroke, compression ignition engines |
| Owner | Private investors including Sequoia Capital, RockPort Capital Partners, Madrone Capital Partners, Triangle Peak Partners, Interwest Partners |
| Website | achatespower |
Achates Power is a U.S.-based company located in San Diego that specializes in developing opposed-piston, two-stroke, compression ignition engines tailored for both commercial and passenger vehicles. Established in 2004 by entrepreneur James U Lemke, the firm concentrates on advancing fuel economy and minimizing emissions through its cutting-edge engine architecture.
The opposed-piston engine developed by Achates Power has shown notable improvements in fuel consumption while adhering to rigorous tailpipe emissions standards. In 2018, the California Air Resources Board awarded the company close to $7 million to validate that its Class 8 heavy-duty engine complies with ultralow NOx and greenhouse gas mandates. This 10.6L powerplant, installed in a Peterbilt 579 truck operated by Walmart, delivered up to a 21% increase in fuel efficiency over conventional benchmark vehicles and satisfied all EPA and CARB emissions standards set for 2027 throughout an 800,000-mile service life using standard aftertreatment technologies. These findings were published in a technical paper presented at the 2025 SAE World Congress.
From a strategic standpoint, Achates Power has cultivated crucial partnerships to broaden its market reach and accelerate technology adoption. In 2012, it became a subcontractor for AVL Powertrain Engineering supporting the U.S. Army’s next-generation combat engine program. The following year, it entered into a joint development and licensing partnership with Fairbanks Morse Engine aimed at improving emissions performance and fuel efficiency of opposed-piston engines. By 2017, Cummins and Achates Power were collaboratively selected by the U.S. Army to develop the Advanced Combat Engine delivering 1000 horsepower—a compact, efficient propulsion system envisioned for future military applications.
As a privately owned entity, Achates Power counts prominent investors such as Sequoia Capital, RockPort Capital Partners, Madrone Capital Partners, Triangle Peak Partners, and Interwest Partners among its backers. The company’s growth strategy leverages strategic alliances and government contracts to expand its presence in both commercial transportation and defense sectors.
Engine
The Achates Power opposed-piston engine draws inspiration from the 1930s Junkers Jumo 205/207 aircraft engine design and features two pistons within each cylinder that move toward each other. This configuration eliminates the need for a cylinder head and valvetrain, thereby reducing thermal losses, frictional drag, manufacturing complexity, and costs. The two-stroke operation further boosts efficiency by shortening combustion duration for optimal timing and allowing for smaller displacement compared to traditional four-stroke engines.
While opposed-piston engines had declined due to modern emission regulations, Achates Power holds patents on innovations enabling compliance with current standards. In 2025, the company partnered with Argonne National Laboratory to demonstrate hydrogen-fueled direct-injection compression-ignition combustion in a single-cylinder opposed-piston engine, achieving indicated thermal efficiencies reaching 47%. This milestone underscores Achates Power’s dedication to advancing clean engine technologies.
Emission reduction claims
Achates Power maintains that its two-stroke opposed-piston design emits lower nitrogen oxides (NOx) than equivalent four-stroke engines. Contributing factors include:
- Accelerated warm-up of the Selective Catalytic Reduction (SCR) system
- Improved management of Exhaust Gas Recirculation (EGR) through controlling pressure differentials between intake and exhaust manifolds
Development timeline
2004: James Lemke established the company with financial backing from John Walton, son of Walmart's founder Sam Walton.
2005: Initial engine trials commence within the company’s own testing facility.
2007: A Series A funding round is secured, led by Sequoia Capital; the company also obtains a DARPA contract focused on designing lightweight engines for UAVs.
2008: Engine testing accumulates to a total of 500 hours.
2009: A second test cell becomes operational; Series B investment round completed, spearheaded by Triangle Peak Partners.
2010: Engine successfully meets NATO’s 50-hour durability standard; total testing time surpasses 1,000 hours; facility grows with the addition of another test stand.
2011: Aggregate engine testing hours exceed 2,500.
2012: The A48 opposed-piston engine fires for the first time; testing surpasses 3,600 hours; chosen alongside AVL Powertrain Engineering by the U.S. Army to develop next-generation combat engines.
2013: Honored with the Frost & Sullivan North American New Product Innovation Award; testing exceeds 4,500 hours; named runner-up for the SAFE Energy Security Prize; enters into a joint development and licensing partnership with Fairbanks Morse Engine.
2014: Engine testing on dynamometers surpasses 5,000 hours; publishes a comparative analysis on light-duty diesel engine efficiency.
2015: Receives a $14 million contract from the U.S. Army to advance engine development for forthcoming combat vehicles.
External links
- Achates Power Official Website
- Prospects for Overhaul of Combustion Engine, Bloomberg TV. September 21, 2011.
- Start-Ups Work to Reinvent the Combustion Engine, New York Times. March 30, 2011.
- 25 Companies to Watch in Energy Tech, Bloomberg Businessweek. July 14, 2009.
- 8 Greentech Trends to Watch, CNN Money. May 11, 2011.
- Cheap, High MPG Engines--But. . ., Automotive News. March 5, 2012.
- An Engine That Uses One-Third Less Fuel. . ., MIT Technology Review. January 14, 2013.
- Opposed Piston Engines Website