do88 BMW B58 Gen 2 (M240I/M340I/M440I/Supra) Auxilliary Radiator

The B58 Gen 2 cooling system uses three frontal radiators, one large central radiator and two smaller auxiliary radiators positioned in front of each wheel. Tuned engines produce significantly more heat, making it genuinely challenging to maintain optimal engine temperatures during intense street, track, or drag strip driving. The OE auxiliary radiators use slim cores and plastic tanks, not ideal for tuned cars pushing beyond factory power levels.

Fortunately, the available design space allows for both increased frontal surface area and core thickness on both sides of the car. The OE radiator is identical for both sides, and do88's Performance Radiator is designed the same way, a genuine drop-in replacement for either the left or right position. The double-row core measures a substantial 40mm thick, expanding cooling surface area considerably over the factory slim-core design, with all-aluminium construction and durable TIG-welded end tanks replacing the OEM's plastic tanks. Installation uses CNC-machined mounting brackets and OE-style quick-connect inlet/outlet connections, and the OE stone guard can be easily attached to this radiator for continued protection against road debris.

Important: for M240i, M340i, M440i, and Z4 applications, this radiator is only suitable for cars fitted with the factory remote radiator (OE part 17118672237) on the right side, included as part of the M Technology Package (option code 33T). Confirm your car has this factory-fitted before ordering. The Toyota GR Supra fitment does not carry this restriction.

Sold individually. do88 recommends upgrading both sides together for the best result, order a quantity of 2 for a full left and right set.

Why Choose This Auxiliary Radiator

• Increased frontal surface area and core thickness over the factory slim-core design
• 40mm double-row core, a genuine step up from the OEM's slim single-row unit
• All-aluminium construction with durable TIG-welded end tanks, replacing OEM plastic tanks
• Increased liquid volume for optimal heat dissipation
• CNC-machined mounting brackets and OE-style quick-connect fittings for easy installation
• OE stone guard compatible, continued protection against road debris

Compatibility

• Toyota GR Supra MK5 (A90, 2020+, B58)
• BMW G42 M240i/M240iX (B58, 2022+) — requires factory remote radiator (option 33T)
• BMW G20/G21 M340i/M340iX (B58, 2018+) — requires factory remote radiator (option 33T)
• BMW G22/G23/G26 M440i/M440iX (B58, 2021+) — requires factory remote radiator (option 33T)
• BMW G29 Z4 M40i (B58, 2017+) — requires factory remote radiator (option 33T)

Sold individually. Order quantity 2 for a complete left and right set.