CSF Auxiliary Radiator (BMW F80 M3, F82 M4, F87 M2C)M3 F80 CSF Auxiliary Radiator Note: if you require TWO CORES, add 2x quantity at checkout. Like the other cooling systems on the F8X, the factory auxiliary radiators do a pretty good job in stock form. However, once you start adding a lot of power and pushing the car in aggressive driving conditions, the factory systems start to show its limitations. As more and more owners have pushed the limits of their S55, CSF saw the need and demand. The F8X