K-TUNED HIGH PRESSURE RADIATOR CAPK Tuned High Pressure Rad Caps were designed specifically to end the confusion over which cap is used with our upper coolant neck filler option. Also keep in mind that these rad caps can also be used on the actual rad neck on several applications. Our high pressure caps increase the system pressure before opening from 1. 1 to 1. 3 kg cm. This effectively raises the boiling point of the coolant which in turn improves overall cooling performance. The