The TwinAir Ice Flow Radiator Cap increases the boiling point of water in your motocross radiator by increasing the pressure inside the radiator. The difference between a stock radiator cap and a high pressure cap is dramatic.
The radiator cap on a motorcycle is similar to the safety valve found on a pressure cooker cauldron like a Presto. Since the boiling point of water increases when water is pressurized, a radiator cap has a coil spring located between two rubber gaskets. The stiffness of the spring will determine the water pressure. As the water heats up, it expands. This expansion puts pressure on the radiator cap spring. When the internal pressure of the radiator exceeds the spring force of the radiator cap, hot coolant escapes and overflows between the two rubber seals and comes out through the overflow hose. But until the spring tension is overcome, the water will not boil.
Without any pressure, the water will boil at 212 degrees Fahrenheit (at standard temperature and barometric pressure); however, a cooling system pressurized below 15 pounds will allow pure water to reach 250 degrees before boiling. For every pound of pressure exerted on the coolant, the static boiling point is increased by 3 degrees.
Most Japanese motocross bikes come with a 1.1bar Radiator Cap, while KTMs and Husqvarna come with a 1.8bar Radiator Cap. The 1.1bar cap can withstand 14.22 psi before the coolant opens the valve and steam comes out of the overflow. By increasing the radiator cap to 1.8bar, the radiator can withstand 25.6 psi, while a 2.0bar caps out at 28.45 psi. The higher the pressure, the longer the water in your radiator will resist boiling.
Twin Air offers a 1.8bar radiator cap to replace the original 1.1bar caps on Japanese motocross brands like Honda, Yamaha, Kawasaki and Suzuki. For KTM and Husqvarna, they are delivered with 1.8bar caps, you can replace them with a 2.0bar cap.