High-Performance Auxiliary Radiator | BMW G8X M2/M3/M4

Engineered Cooling for Pushed S58 Builds The CSF Auxiliary Radiators are a natural extension of the proven G8X cooling architecture—but they’re purpose-built for cars that live beyond factory limits. In stock form, the OE auxiliary radiators perform well. Once power is increased and the car is driven hard—extended pulls, track sessions, high ambient temps—the factory system begins to show its ceiling. That’s where CSF steps in. As S58 owners continue to extract more performance, maintaining thermal stability becomes critical. These auxiliary radiators are designed to keep temperatures in check when it matters most. Motorsport-Grade Design Backed by 50+ Years of Expertise With over five decades of radiator engineering experience, CSF brings true motorsport cooling technology to the G8X platform. These high-performance auxiliary radiators are equally at home on the street or the track, making them an essential upgrade for high-horsepower builds and serious driving environments. At the core is CSF’s proprietary 2-row B-Tube technology . Unlike conventional oval (“O-tube”) designs, CSF’s brazed B-shaped tubes increase internal surface area by approximately 15%, improving heat transfer while allowing the use of thinner, lighter aluminum. The result is greater efficiency, increased structural strength, and dual-path laminar coolant flow within the same physical footprint. To complement the tube design, CSF employs ultra-efficient multi-louvered fins that are precisely aligned to maximize airflow through the core. Fin geometry is application-specific and validated in CSF’s wind-tunnel testing to ensure maximum heat rejection under real-world conditions. True Drop-In Fit, Built to OEM+ Standards CSF G8X M3/M4/M2 Auxiliary Radiators are engineered as a true drop-in solution with no cutting or modification required. CNC-machined, OE-style brackets provide durability and precise fitment, while inlet and outlet connections are designed to match factory interfaces—allowing reuse of OEM or aftermarket hoses. When reliability, fit, and thermal performance matter, these auxiliary radiators deliver cooling headroom you can trust—engineered to support the way your CarBahn-equipped G8X is meant to be driven. CSF Part Number: 8321