EPS has been testing the Proof-of-Concept Engine on its mobile test stand since November 2011. In a program known in the automotive world as “accelerated durability testing,” the team has run the engine through extremes that will never be experienced in the course of normal aircraft operations, including calibrations, low inertia props, cold tests, multiple rapid acceleration and deceleration cycles, and a battery of other insults to put the engine through its paces. In the summer of 2013, EPS drove the engine to the top of Mount Evans in Colorado to conduct high altitude performance tests at 10,000 and 15,000 MSL. The engine achieved full 350 horsepower operation at 15,000 feet density altitude and achieved 420 horsepower at low altitude. The engine’s liquid cooling system has been tested in extreme weather conditions, demonstrating starts in temperatures from – 25 degrees F to more than 100 degrees F. Based on hundreds of hours of testing as of April 2014, EPS can report significant technical breakthroughs, including:
• Extremely low vibrations that allow the engine to safely operate aluminum propellers, a feature unique to the EPS diesel engine and verified by extensive testing conducted in cooperation with Hartzell Propeller Inc.
• A liquid cooling system that operates reliably at any outside air temperature or altitude
• A reliable, rugged and light steel piston design that eliminates piston failures common to aluminum pistons that are found in all other aviation engines
• A Compacted Graphite Iron (CGI) Cylinder Block that will avoid the fatigue cracks that plague aluminum aviation crankcases; yet the CGI block is just as light as its aluminum equivalent
• Measured fuel consumption <10 gal/hr at 65% power (227 hp)