Cummins Advanced Combat Engine (ACE) Displays Revolutionary New Capabilities

Cummins Advanced Combat Engine (ACE).

An opposed-piston diesel engine that works on a two-stroke combustion cycle and produces roughly 1,000-horsepower without the need for a valvetrain may sound like a work of engineering-fiction but this is exactly what Cummins recently delivered for the defense industry.

Specifically tailored for the unique needs of the defense industry, Cummins Advanced Combat Engine (ACE) has just four cylinders but eight pistons.

Testing for ACE began in 2019 at the U.S. Army Tank Automotive Research, Development and Engineering Center (TARDEC). Based on testing, the new engine is projected to deliver a 21 percent reduction in thermal rejection, a 50 percent increase in power density and a 13 percent jump in fuel efficiency.

The flat-four two-cycle configuration requires the use of a supercharger in order to force air into the combustion chamber. The 1,000 hp output is delivered at just 2600 rpm thanks to the duel Holset® HE500 variably geometry turbos. This helps with engine longevity and durability which are essential for military operations.

A special consideration that went into the engineering of ACE was to ensure that it could fit into the engine compartments of tanks such as the M88. This, along with the need to better manage thermal efficiency were driving factors in the decision to go with a unique opposed-piston design.

Cummins ACE is just one recent example of Cummins continuous commitment to innovation for the defense industry. Learn more about Cummins efforts at