Fuji Heavy Industries Ltd. (FHI), Subaru's parent company, has released details on its third-generation four-cylinder boxer engine that will be available in 2.0-liter and 2.5-liter displacements. This is the first overall renewal since the second generation was introduced in 1989. The horizontally opposed flat 4 has been a mainstay of Subaru's Impreza, Forrester and Legacy models for some time.
Subaru claims that fuel efficiency is up by 10%, thanks to a compacter combustion chamber and longer stroke, variable-valve timing (which Subaru calls Active Valve Control System) on both the intake and exhaust valves, lighter pistons and connection rods, a more efficient and compact oil pump and separate engine cooling circuitry for both the block and head.
The new boxer engine has a slightly higher compression ratio of 10.5 (up from 10.2), a shorter bore (84 mm, down from 92) and longer stroke (90 mm, up from 75). Subaru has yet to release details about changes to the 2.5-liter unit.
The first Subaru to receive the third-generation boxer engine will be the Forester.
By Tristan Hankins