[BMWDavid]

Take a look at the Porsche 4.0L GT3-RS, 500 HP. That's 125 HP per liter. Engine revs to 8500 rpm. Has many costly bits inside; Ti rods, ported heads, fancy valve springs and etc. Don't forget that Porsche has variable valve timing as well as a different valve lift at a higher rpm.

So the FA20 @ 2L would be at 250 HP if Subaru went this way. Surely would be a pricey engine. Now if they took it to 2.5L, about the same cc per cylinder as the Porsche 4.0L, then we are talking 312 HP.

I agree that it should not be a turbo with weight penalty over the front end. Plus a NA engine has a better feel as it revs. Not that a torquey turbo engine is a bad thing, but I think it would be out of charactor for the BRZ.