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Achates Power awarded $14M military single-cylinder engine project; partnering with Cummins

Achates Power, Inc., the developer of a family of two-stroke compression-ignition opposed-piston engines (earlier post), has been awarded a $14-million project by the National Advanced Mobility Consortium to support research and development work of the US Army Tank Automotive Research, Development and Engineering Center (TARDEC). The project is the Single Cylinder Advanced Combat Engine Technology Demonstrator, part of the Army’s 30-year strategy to modernize tactical and combat vehicles.

Achates has partnered with Cummins Inc. for the project. Together, their technologies will be used to further refine the opposed-piston engine for lower heat rejection, greater fuel efficiency, increased power density and the ability to operate on various fuels. The end goal is to deliver a product that improves the mobility and performance of combat vehicles.

In December 2012, TARDEC had awarded Achates Power, Inc. and AVL Powertrain Engineering, Inc. a $4.9-million contract for design and construction of the Next-Generation Combat Engine. (Earlier post.)

With this latest contract, Achates has six concurrent customers whose contracts encompass five different engine applications: passenger vehicle, light commercial vehicle, heavy commercial vehicle, military and marine/stationary power. Achates Power's engine allows OEMs to achieve the world’s most stringent current and future fuel efficiency and emissions standards, which include EPA 2010, Euro 6 and Tier 3/LEV 3, among others, without additional cost or complexity.

This award builds upon 10 years of extensive development by Achates Power to modernize and optimize the opposed-piston engine. With Cummins as our partner on the Single Cylinder Advanced Combat Engine Technology Demonstrator program, we have the opportunity to combine Cummins’ strengths in diesel engine leadership with our strengths in opposed-piston engine technology to deliver a superior engine for combat and tactical vehicles for the US Army.David Johnson, CEO, Achates Power

Achates Power has realized the potential for impressive efficiency in their development of the opposed piston architecture. We have worked with Achates Power for a number of years now and applaud their engineers and engineering rigor, and we look forward to continuing our collaboration. This contract acknowledges the U.S. Army recognizes the special value of this engine design in their application and Achates Power’s ability to optimize it.

—Dr. John Wall, chief technical officer, Cummins Inc.

When speaking about the Single Cylinder Advanced Combat Engine Technology Demonstrator, Dr. Walter Bryzik, professor of Mechanical Engineering at Wayne State University College of Engineering, retired chief scientist of TARDEC and a member of Achates’ Industry Advisory Board, notes:

Three features are critically important for combat vehicles: low heat rejection to coolant, high power density, and high efficiency. The opposed-piston engine architecture—particularly with the advances from Achates Power—has strengths in all three areas.

The Army is seeking to leverage these capabilities into an extremely compact propulsion system.

Opposed piston engines (OPE) offer a number of fundamental efficiency enablers compared to four-stroke engines:

  • Lower heat transfer
  • Leaner combustion
  • Optimally phased and faster combustion at equivalent pressure rise rate
  • Lower pumping work

At the Symposium on International Automotive Technology 2015 in India in January, Achates Power presented Achates Power presented work related to the first opposed-piston multi-cylinder engine fuel economy demonstration meeting US 2010 emissions standards.

The results showed that the research 4.9L three cylinder engine was able to achieve 43% brake thermal efficiency at the best point and almost 42% on average over the 12 modes of the SET cycle. The results from this test confirmed the modelling predictions and carved a very robust path to a 48% best BTE and 46.6% average over the cycle for a production design of this engine.


  • Redon, F., Sharma, A., and Headley, J. (2015) “Multi-Cylinder Opposed Piston Transient and Exhaust Temperature Management Test Results” SAE 2015-01-1251


Liviu Giurca

A much improved version having opposed piston and internal heat recovery is described in:
This can get the Carnot efficiency limit.


What a waste of resources for R&D for something that is already available.
But they'd have to go begging at Mercedes because these duds have their meat-hooks on this innovation.

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