The High Pressure Radiator Cap raises cooling system pressure from 1.1 to 1.3 bar.
This in turn increases the boiling point, thereby reducing the risk of overheating the engine under high speeds or loads.
The cap utilises silicon rubber for heat resistance & increased durability, and is identifiable by the bold STI logo situated on the top of the cap.
As used by Subaru Rally Team Australia on the championship winning Group N rally cars