BULL BOOST PERFORMANCE Performance Cylinder 4 Coolant Mod for Subaru WRX STI EJ20/EJ25 Engines

BULL BOOST PERFORMANCE Performance Cylinder 4 Coolant Mod for Subaru WRX STI EJ20/EJ25 Engines

Part Number: 720053572377

Improve cooling balance across your Subaru EJ engine with the BULL BOOST PERFORMANCE Cylinder 4 Coolant Mod. Designed to increase coolant flow specifically to cylinder #4, this upgrade helps reduce localized hot spots and promotes more even temperature distribution across all cylinders.

By improving coolant flow to cylinder 4, this modification helps reduce the risk of knock and detonation—two common contributors to EJ-series engine failures such as ringland damage. Ideal for performance builds, track cars, and modified daily drivers.

Features

• Direct coolant flow upgrade for cylinder #4
• Helps reduce cylinder 4 coolant temperatures
• Promotes more even engine cooling across all cylinders
• Reduces risk of knock and detonation
• Improves long-term engine reliability in tuned applications
• Simple bolt-on style installation

Fitment

Compatible with Subaru EJ-series engines:

• EJ20 engines
• EJ25 engines

Vehicle Applications:

• 2002–2014 Subaru WRX
• 2004–2020 Subaru STI
• 2004–2008 Subaru Forester XT
• 2005–2009 Subaru Legacy GT

Package Includes

• (1) Cylinder 4 Coolant Mod
• (1) T-Fitting
• (2) Hose Clamps

Notes

• Installation recommended for experienced builders or professional shops
• Designed for performance and reliability-focused cooling improvements

All warranties, claims, and product-related issues must be handled directly through BULL BOOST PERFORMANCE.