Subaru FA engine


The Subaru FA engine is a gasoline boxer-4 engine used in Subaru and Toyota automobiles. It is a derivative of the FB engine, however, efforts to reduce weight while maintaining durability were the main goals of the FA engine. While the FA and FB engines share a common platform, the FA shares very little in dedicated parts with the FB engine, with a different block, head, connecting rods, and pistons.

Development

The FA series engine was developed for the Subaru BRZ and the first FA engine, the FA20D, was designed to be mounted as low as possible and to minimize the polar moment of the chassis to improve dynamic response and handling. The FA engine features a shallower oil pan and shorter intake manifold to reduce overall engine height compared to the Subaru FB engine. The FA and FB engines share few parts.
A direct injection-only turbo variant of the FA20, the FA20F, was introduced in late 2012 with the 2012 Legacy GT and in the United States, the 2014 model year Subaru Forester. Compression ratio for the turbo engine falls to 10.6:1 from 12.5:1 for the FA20D. A revised variant of the FA20F was introduced for the 2015 model year Subaru WRX; in this application, the camshafts, rocker arms, boost pressure, intercooler, and exhaust were revised to increase peak output.

FA20

Compared to the FB20 engine, which is undersquare with an bore and stroke for swept displacement, the FA20 is perfectly square with an bore and stroke for swept displacement. The bore and stroke are also reminders of the heritage Toyota model AE86.

FA20D

The FA20D features both direct and port injection and Subaru AVCS variable valve timing system. It is used in the Subaru BRZ, and is identified by a Toyota engine family code known as the 4U-GSE, which is installed in the Toyota 86 and the Scion FR-S. According to Subaru, 0W-20 oil is recommended.
Wards Auto put the FA20D on their "10 Best Engines" list for 2013.
A version with Subaru's own direct fuel injection and twin-scroll turbocharger was introduced in 2012. The FA20F was named to the Wards Auto "10 best engines" list in 2015 and 2016.

FA24

FA24F

The FA24F was introduced in 2018 initially for the 2019 model year Subaru Ascent. The bore is increased compared to prior FA20 engines, increasing displacement to. The engine has an all aluminum head and block in order to keep weight and warm-up times low. Direct injection and a turbocharger are used to provide output comparable to a 6-cylinder naturally aspirated engine, and the FA24 uses "regular" fuel. At the 2019 Chicago Auto Show, Subaru unveiled the 2020 model year Subaru Legacy sedan, available starting in fall 2019 and featuring the FA24 as the uplevel engine option. The 2020 model year Subaru Outback also featured the FA24 as the uplevel option.