Japanese leading engine maker IHI Corp. said Wednesday a subsidiary has falsified fuel efficiency data for 4,361 engines, mostly for ships, produced at least since 2003 for the domestic and overseas markets.

The data-rigging was found at IHI Power Systems Co.'s plants in Niigata and Gunma prefectures, with data doctored during tests to make their fuel economy look better, IHI said.

Of the 4,361 engines, 2,058 did not meet the specifications set under contracts with its customers, according to IHI.

IHI Corp's Senior Executive Officer Hideo Morita (R) speaks at a press conference over falsified fuel efficiency data in Tokyo on April 24, 2024. (Kyodo)

"It is a betrayal of our customers' trust," IHI Senior Executive Officer Hideo Morita said at a press conference. "We are in a grave situation in which the foundation of our manufacturing has been shaken."

Among the affected engines, some are used in Japan Coast Guard patrol vessels and others in Hokkaido Railway Co. trains and in fishing boats owned by some municipalities, IHI said.

The misconduct came to light after a whistleblower within the subsidiary reported the wrongdoing in February.

Japan's transport ministry the same day instructed IHI and the subsidiary to look into the matter and come up with measures to prevent similar incidents from happening again.

In 2019, IHI admitted to misconduct in the manufacturing process of its aircraft engine parts, which prompted the transport ministry to order the company to improve operations.

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