Performance Koyo Radiator, BMW Z4, 3.0L, 2018+, Toyota Supra, 3.0L Engine, 2020+, 48mm, (KH423660)

Koyo HH Series Remote Radiators (Left & Right) — KOYO-KH423660 / HH423660

High-Density Twin Radiator Upgrade for Toyota A90 Supra & BMW Z4 (B58 Engine)

Koyorad introduces its high-performance all-aluminum auxiliary (remote) radiators for the 2020+ Toyota Supra GR A90 and 2018+ BMW Z4 (G29) with the 3.0L I6 B58 Turbo engine. These HH Series radiators are engineered as a direct-fit replacement for the OEM side-mounted radiators, significantly enhancing heat dissipation and long-term durability.

Designed to perfectly integrate with OEM air ducts and rock guards, Koyo’s twin Hypercore radiators retain all factory mounting provisions and quick-connect fittings. The 48mm Hypercore is nearly 80% thicker than OEM, greatly increasing thermal efficiency and endurance — ideal for spirited street driving or aggressive track use.

Features:

• Includes Left & Right Radiators: Full pair for direct replacement of both auxiliary units.

• 48mm High-Density Hyper Core: Significantly improves coolant capacity and thermal transfer vs. OEM.

• All-Aluminum Construction: Replaces failure-prone plastic tanks with TIG-welded, furnace-brazed durability.

• OEM Fitment: Retains factory quick-connect fittings, air guides, shrouding, and rock guards.

• Easy Installation: Installs with basic hand tools in approximately 30 minutes per side.

• Precision Engineering: Triple pressure tested for leak-free reliability; engineered for exact fit and factory airflow dynamics.

OEM Cross Reference:

• OEM Part Numbers: 16400WAA04, 17118672237

• Koyo Part Numbers: KH423660 (International) / HH423660 (Koyorad USA)

Vehicle Fitment:

• Toyota Supra GR (A90) — 2020+

• BMW Z4 (G29) — 2018 to current
  (Both with 3.0L B58 I6 Turbo engine)

Installation Notes:

• Reuses OEM rock guards and air guides

• Follows OEM coolant fill procedures

• Left and right radiators included in packaging

Customer Reviews

⭐️⭐️⭐️⭐️⭐️
"Massive cooling upgrade for the A90 Supra! These radiators dropped coolant temps noticeably during back-to-back sessions on track. The install was simple — everything just clipped right in like stock. Worth every cent."
— Anthony D.

⭐️⭐️⭐️⭐️⭐️
"The OEM aux rads started showing signs of fatigue after a year of hard driving. These Koyos feel bulletproof. Quality welds and fitment were spot on. Car runs cooler and no more worries about cracked end tanks."
— Rachel M.

⭐️⭐️⭐️⭐️
"Packaging and build quality were excellent. Install took under an hour total. I’d give 5 stars if the instructions were a bit more detailed for first-timers, but overall very happy with the product."
— David Y.