According to Subaru, higher strength material for the connecting rod bolts enabled higher pressure to be withstood in the cylinders.
Furthermore, the connecting rod bearings were made from a copper-based alloy.
Furthermore, roller lifters were used as contacts between the pump and camshafts to reduce friction; a pulsating damper was also integrated in the pump to reduce fuel pressure fluctuations.
In addition to preventing changes in bore shape, this design cooling around the deck surface and raised the knock limit.
Through the use of oil pressure and spring force, the lash adjuster maintained a constant zero valve clearance.
Specifications for other markets may vary.