This new Boxer Four is the third generation of Flat Fours that have been around in one version or another since 1966. This first came in a small 1.0liter for the Subaru 1000, the second version was first placed in a Subaru Legacy in 1989 and now, this new engine will begin its services in the Subaru Forester and then to the other models.
The improvements made to the engine have basically improved fuel consumption figures by 10% and has also improved torque levels. Information of the 2.0liter normally aspirated engine has been given as an example. The new 2.0liter makes the same 148bhp but gets a small hike in torque - 196Nm instead of 191Nm.
The improved torque figures mostly come from the fact that this engine is now a longer stroke engine. The bore and stroke of the engine is now 84x90mm against 92x75mm, effectively making this an oversquare type engine which usually generates more torque at the expense of revs. I suppose this shouldn’t be the case as engine technology has improved since the days where long stroke engines hate to rev.
The new engine gets a higher compression ratio of 10.5:1 from 10.2:1 and gets the usual Subaru AVCS valve timing systems and improved Exhaust Gas Recirculating/Emissions systems. The fuel consumption also gets a boost due to more lightweight parts in use, like a compact oil pump which helps the new engine make 30% less friction losses. It also has improved cooling in the engine block and cylinder head. This means less energy losses from heat and also friction for this new engine.
This new engine shall now come in 2.0liter and 2.5liter versions for now. Those that wonder whether the smaller 1.5liter Boxer will have this new setup should know that Subaru only recently revamped the 1.5liter a few years ago. It has some of the new stuff like the AVCS as well as long stroke of this new engine (79mm stroke opposed to 65.8mm before making nearly as much torque – 142Nm as the older more basic EJ16 -143Nm engine used in the older GD chassic Impreza 1.6TS before this).