Through the use of oil pressure and spring force, the lash adjuster maintained a constant zero valve clearance.
In addition to preventing changes in bore shape, this design cooling around the deck surface and raised the knock limit.
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.
Furthermore, the connecting rod bearings were made from a copper-based alloy.
Furthermore, the intake ports and the diameter of the intake valves were designed to create a swirling effect for the air as it entered the combustion chamber.
Furthermore, cooling slits between the cylinder bores provided water cooling channels.
According to Subaru, higher strength material for the connecting rod bolts enabled higher pressure to be withstood in the cylinders.
Furthermore, the stem shape and tapering of the small end reduced connecting rod mass.