J-ENG: testing complete, 2-stroke ammonia engine ready to roll out

By Julian Atchison on September 02, 2025

Installation aboard mid-sized gas carrier this October

J-ENG employees in front of the two stroke ammonia engine.

Click to learn more. J-ENG’s two stroke ammonia engine, which successfully passed performance verification tests in late August. The first unit will be installed onboard a newbuild vessel in October, hitting the water in 2026. Source: Japan Engine Corporation.

Japan Engine Corporation (J-ENG) has announced commercial readiness for its new 2-stroke, dual-fuel engine. The 7UEC50LSJA-HPSCR (50 cm bore, 7 cylinders, with high pressure SCR for exhaust after-treatment) has been under-development since 2023 as part of a government funded project, with NYK Line, Nihon Shipyard, Japan Marine United Corporation, and ClassNK part of the consortium. The first engine unit will be delivered to the JMU Ariake Shipyard in October 2025, and then installed on an AFMGC (ammonia-fueled medium gas carrier), scheduled to enter service in 2026.

Rigorous testing

J-ENG reports that “official test runs” were conducted in late August, under the supervision of project consortium partners. A series of performance verification tests were carried out in both ammonia fuel and heavy fuel oil operation modes. This follows on from two rounds of initial tests: 1,000 hours on an ammonia-fueled, single-cylinder test rig between May 2023 and September 2024, and then 700 hours on a full scale test engine from April 2025, including leak prevention and safety systems.

J-ENG reports that testing data shows that, at 100% engine load and a 95% ammonia fuel (i.e. 5% pilot fuel), N2O emissions are approximately 3ppm, unburned ammonia emissions virtually zero (post-SCR), and NOX emissions half those when running the engine in heavy fuel oil operation mode. This equates to a reduction of over 90% in GHG emissions, with equivalent or higher thermal efficiency when operating in ammonia fuel mode. These results are similar to those reported by WinGD and Everllence in testing their own 2-stroke ammonia engines. Operational data from the mid-sized gas carrier launching in 2026 (as well as independent emissions testing) will help build confidence in the decarbonisation bona fides of ammonia fuel.

J-ENG is also developing a 60cm bore engine for larger vessels, and is proceeding with construction of a new engine manufacturing facility, scheduled to open in 2028. In Jan 2025, J-ENG received $42 million in government funding for the project, under a scheme led by the the Ministry of Land, Infrastructure, Transport and Tourism, and the Ministry of the Environment.