If you just purchased the Koyo Radiator, you can maximize the performance with the Koyo 1.3 Bar High-Pressure Radiator Cap! 

These radiator caps from Koyo is finished in Blue, and reviewers of this radiator cap have been pleased with the looks, and performance of this radiator cap. 

This Koyorad Hyper Cap withstands an increased valve pressure rating of 1.3kgf/cm2 (1.3 bar) (18.9 psi) (130 kPa) which increases the boiling point of water and relieves high-performance engines of excessive heat. These are highly recommended for use with every KoyoRad All Aluminum Radiator (when applicable). 

The KoyoRad Hyper cap is crafted in Japan from high-quality materials to ensure longevity and performance from your KoyoRad Racing Radiator

Note: Product not recommended for use with stock OEM radiator. This cap is intended for use with Koyorad all-aluminum radiator part #VH012663.