HKS 1.1 Bar Limited Edition Radiator Cap - 2002-2024 Subaru WRX / STI / 2011-2014 Forester / 2010-2014 Legacy

HKS 1.1 Bar Limited Edition Radiator Cap - 2002-2024 Subaru WRX / STI / 2011-2014 Forester / 2010-2014 Legacy1. 1 Bar Limited Edition Radiator Cap for Subaru WRX, STI, and Other Models The HKS 1. 1 Bar Radiator Cap is a precision pressure radiator cap for 2002 2024 Subaru WRX and STI, 2011 2014 Forester, and 2010 2014 Legacy applications. The 1. 1 bar pressure rating (approximately 16 psi) is slightly higher than some OEM caps, which raises the boiling point of the coolant and provides a small margin of additional cooling system capacity for high load

1.1 Bar Limited Edition Radiator Cap for Subaru WRX, STI, and Other Models

The HKS 1.1 Bar Radiator Cap is a precision-pressure radiator cap for 2002-2024 Subaru WRX and STI, 2011-2014 Forester, and 2010-2014 Legacy applications. The 1.1 bar pressure rating (approximately 16 psi) is slightly higher than some OEM caps, which raises the boiling point of the coolant and provides a small margin of additional cooling system capacity for high-load driving. The Limited Edition designation refers to the finish and packaging.

Specs & Highlights

• 1.1 bar / approximately 16 psi pressure rating
• Raises coolant boiling point relative to lower pressure caps
• Precision pressure relief valve
• Compatible with OEM and aftermarket overflow systems
• Fitment: 2002-2024 Subaru WRX / STI / 2011-2014 Forester / 2010-2014 Legacy

1.1 Bar, ±0.05 Bar Tolerance, 69mm Wide Neck

The 1.1 bar rating raises the coolant boiling point by approximately 3°C compared to a 1.0 bar cap and approximately 6°C compared to a 0.9 bar OEM cap, when calculated against the 50/50 ethylene glycol/water mixture used in most Subaru cooling systems. The pressure relief valve tolerance is ±0.05 bar, tighter than OEM cap specifications which typically allow ±0.1 bar variance. Cap outer diameter is 69mm, compatible with the standard Subaru wide-neck radiator filler neck used across the WRX, STI, and legacy Forester applications listed.

How Cap Pressure Affects Coolant Boiling Point

Radiator cap pressure directly affects the coolant's boiling point. A higher pressure cap means the coolant must reach a higher temperature before boiling, providing more headroom before a cooling event occurs. For track use, spirited driving, or any high-load situation where coolant temperatures rise, the additional margin of the 1.1 bar cap is a worthwhile investment.

Compatible with Standard Wide-Neck Subaru Radiators

Installation is a direct cap swap. Verify that your overflow reservoir and upper radiator hose are rated for the operating pressure before installing any upgraded radiator cap. The HKS 1.1 bar cap is within the tolerance range of most factory Subaru cooling systems.

The FT Breakdown

The radiator cap is the smallest and cheapest upgrade on the cooling system with a real engineering basis. The HKS cap is a precision part with a consistent pressure valve: not a marketing item. For Subaru performance builds, it is a logical starting point for cooling system work. The ±0.05 bar tolerance is tighter than most OEM cap specifications and significantly tighter than cheap aftermarket replacements. A cap that opens at 0.9 bar instead of 1.1 bar is providing less boiling point protection than its rating implies; a cap that opens too late risks system overpressure. HKS's tight tolerance means the cap you install is actually providing the 1.1 bar protection the specification promises.