Originally Posted by ocellaris
If they stick with the EJ, it will be because the FB doesn't fit as a drop in replacement and they don't want to retool the engine bay for a car that is getting replaced in ~2 years with an all new model. Also FB CVT may be a fitment issue.
I don't mind the EJ, aside from the fact that is uses a timing belt which makes for a costly replacement every 75K miles
Real world MPG between the EJ and the DB doesn't seem to differ by much.
What about an FB25 makes it a non-drop-in replacement for the EJ25 NA motor?
They DID THAT ALREADY, The 2009-10 Forester had EJ. The 2011-current Forester, SAME BODY, has the FB, directly. The SH Forester didn't get a big press hoopla party for that, and nothing else visible from the outside of the vehicle changed. The internal structure didn't change. Aside from maybe wheel design, it would be very hard to tell a 2010 Forester X from a 2011 Forester X, but the engine did change from EJ25 to FB25.
The 2010 Legacy/Outback debuted an engine-cradle arrangment. The engine cradle was meant to offer modularity as to which Subaru engine fits in that chassis.
There is pretty much a ZERO percent chance that the '10 Legacy Engine cradle design was designed to preclude the FB engine fitment, as the FB engine was on the docket for 2011, in the Forester, and has been planned to entirely replace the EJ engine line.
The FB25 has DOHC, and DUAL AVCS, where EJ atmospheric engine does not, and FB25 has a little bit more torque. The FB is also likely designed to accept direct fuel injection at some point, and Legacy/Outback is likely to recieve that before Impreza does, because Legacy/Outback is a better featured, higher margin, higher price point vehicle.
I don't think there is a single thing that makes a problem for dropping an FB25 under the hood of a Legacy or Outback. Legacy GT has a low front turbo, so the front-wrap exhaust is designed similarly, and will fit.
The FB25 Forester uses the age-old Subaru 5-speed manual, and 4-speed auto... it bolts to the same transmissions. It bolts to the same engine mounts, and is likely designed for easy use with the engine cradle, as mentioned.