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.
In addition to preventing changes in bore shape, this design cooling around the deck surface and raised the knock limit.
Specifications for other markets may vary.
According to Subaru, fuel efficiency was improved by reducing coolant flow volume and retaining higher oil temperatures at the cylinder block walls.
The hydraulic lash adjuster — located at the fulcrum of the roller rocker arm — consisted primarily of a plunger, plunger spring, check ball and check ball spring.
While the cylinder block had an open-deck design, Subaru claimed that lowering the water jacket achieved the same block stiffness as a semi-closed structure.