Upstream of each intake port, a metal partition acted as a tumble generator valve TGV to increase air tumble and create vortices within the combustion chamber.
The variable valve lift system only changed the lift of one of the intake valves for each cylinder since the other intake valve always provided high lift.
Furthermore, the coolant flow rate within the cylinder head was increased and improved cooling around the spark plugs and injectors raised the knock limit for more reliable performance.
By using EGR, combustion temperatures were reduced such that the engine was less susceptible to knock and injection timing could be advanced.
Camshafts and dual AVCS The FB20 engine had double overhead camshafts that were driven by a maintenance-free chain.
Effectively replacing the , the FB20 engine was a member of Subaru's third generation 'FB' boxer engine family which also included the , ,.
Block and crankcase The Subaru EJ20X and EJ20Y engines had an aluminium alloy block with 92.
According to Subaru, higher strength material for the connecting rod bolts enabled higher pressure to be withstood in the cylinders.