Prior to 1966, Subaru was known for producing kei cars in Japan; for their first four-passenger model, the firm developed an air-cooled boxer engine for a prototype of the Subaru 1500 in 1960, but Fuji Heavy Industries was unable to continue development due to a shortage of funding.

The engine disappeared from the sedan catalogs in September 1975, as the new emissions regulations would simply make the car too slow.

As commercial vehicles didn't have to meet the new stricter regulations, it continued to be available in the Van 1200 Standard until the end of production of the first generation Leone in 1979.

This engine used twin Hitachi carburetors on a single intake manifold, and the late version for the 1983 Safari Rally, featured two downdraft Weber Carburetors, each one mounted directly over each head.

The Heads and Valvetrain on the EA81S engines are different from the regular counterparts, featuring different positions for the intake and exhaust valves on the Heads, feature known usually as Reverse Valves.

Most of the technical advancements introduced to the EA82 were utilized in the next generation Subaru EJ engine, specifically, the SOHC valvetrain, and multi-point fuel injection.

The EA-82T engine was introduced in 1984 for the Third generation of Subaru Leone in the GL-10 and RX Turbo trim models plus the XT (Vortex), and later on the Subaru Leone RX Coupe models.

It is a turbocharged version of the MPFI EA-82 with modified cylinder heads, lower compression pistons, and boost pressure of 7 psi (0.48 bar).

The ER series is a flat-6 engine with a displacement of 2.7 L manufactured by Subaru, a division of Fuji Heavy Industries.

The oil and water pumps are unique to the ER27, sharing similar bolt patterns and design to the EA82, but being of a higher flow in both cases.

[4] The intake manifold uses a two piece design with a lower section bolting to the heads containing the coolant bridge, injectors and various vacuum lines.