Among the components designed to weigh less in the FB engine are:
- Connecting rods shaped to help keep engine width the same as the EJ while allowing longer stroke
- Pistons with a smaller bore, requiring less material and having less reciprocating mass
- Wrist pins with smaller diameters, requiring less material
Along with an efficient and compact oil pump, the lightweight components reduce friction loss by approximately 30 percent, improving fuel efficiency and engine response.
The double overhead camshafts are driven by chains rather than toothed belts. The chains are maintenance free and do not require replacement, helping to lower the cost of ownership.
The use of chain drive allows smaller sprocket diameters at the crankshaft and camshafts. That helps to keep engine width within convenient dimensions.
Compared with the previous non-turbocharged EJ25 engine, the FB25 produces:
- The same horsepower, but at lower rpm
- Slightly higher torque at lower rpm
- Improved fuel economy
That makes the Forester's new FB SUBARU BOXER engine more responsive, especially at lower engine speeds, while allowing the vehicle to travel farther on the same amount of fuel.