The horizontally opposed engine has been a signature mainstay of Subaru vehicles since 1966. Last redone in 1989, the automaker completely remade its well-proven workhorse for 2011, incorporating a comprehensive series of changes that enhances overall performance, lowers emissions and generates roughly a 10-percent bump in fuel economy. Initially available in 2.0- and 2.5-liter four-cylinder incarnations, this all-new engine family is set to become the primary motivator for Subarus worldwide. Its first U.S. application will be in 2.5-liter form under the hood of the 2011 Subaru Forester that goes on sale later this fall.
A showcase for Subaru's technical expertise in the boxer engine design arena, this new-gen flat-four is based around a more compact cylinder design that features a smaller bore and far longer stroke dimensions, a combo that fosters better combustion efficiency and improves mid-range torque. Other key technologies include a new Active Valve Control System (AVCS) on both intake and exhaust valves, special efficiency-optimizing partitions within the intake ports, individualized cooling circuits for the block and head plus a bump in compression ratio. Complementing those feature are a more extensive use of even lighter-weight internal components and a new oil pump that cuts friction loss by nearly 30 percent.
This new Subaru engine family is being manufactured at an equally new, state-of-the art facility outside of Tokyo. In making the announcement, Subaru's parent company, Fuji Heavy Industries, stressed that the new boxer-four was created with both expandability and the potential to for future upgrades in mind, on both the environmental and performance fronts.