SPOOLOGIC 3in Turbo Downpipe

The SPOOLOGIC SL-520-023 3-Inch Turbo Downpipe upgrades the exhaust path on 2015.5–2016 Chevrolet Silverado and GMC Sierra pickups equipped with the 6.6L Duramax LML and a three-bolt lower exhaust connection. Mandrel-bent 3-inch tubing replaces the restrictive factory passage, while preinstalled heat wrap helps limit radiant heat around surrounding components. The black-finished pipe uses a turbo-side V-band flange, a bolted lower flange and a mounting bracket for the matching late LML layout.

Features

• 3-inch mandrel-bent tubing provides a smooth exhaust flow path
• Designed to reduce restriction after the turbocharger
• Preinstalled heat wrap helps limit radiant heat transfer
• V-band-style turbo connection and three-bolt lower exhaust flange
• Welded threaded ports
• Integrated mounting bracket
• Black exterior finish

Performance Benefits

The downpipe carries exhaust away from the turbocharger. Its 3-inch mandrel-bent tubing provides a smoother flow path than the flattened, restrictive sections of the factory pipe, helping reduce restriction after the turbine and support throttle response under load. Preinstalled heat wrap helps limit radiant heat transfer to nearby wiring, hoses and other components. Actual changes in performance and exhaust gas temperature depend on the complete exhaust system, engine condition and operating load.

What’s Included

• (1) 3-inch turbo downpipe with welded flanges, threaded ports and mounting bracket — SL-520-023
• (1) Heat wrap — preinstalled
• Heat-wrap retaining clamps — preinstalled

Common Downpipe Leak Symptoms

• Soot around the turbo outlet, downpipe flanges or pipe joints
• Ticking or hissing that becomes more noticeable under load
• Visible cracks, damaged sealing surfaces or severe corrosion
• Rattling caused by a loose mounting bracket or contact with nearby components

Inspect the downpipe, connections and supports to confirm the source of the problem. These symptoms can also come from other exhaust components.

Installation Notes

Check the lower exhaust connection before removing the original pipe. Transfer the required original sensors and exhaust fuel injector connections to the matching ports, following the factory service procedure. Inspect the turbo outlet clamp, lower connection and mounting hardware, and renew disturbed seals as required. Align the pipe and support bracket before final tightening, maintain clearance from wiring and hoses, and check all serviced connections for leaks.

Fitment

• 2015.5–2016 Chevrolet Silverado GMC Sierra 2500 3500 — 6.6L Duramax LML with a three-bolt lower exhaust connection

⚠️ Check the connection where the bottom of the downpipe meets the exhaust system, especially on 2015 trucks. This version requires the three-bolt lower flange. For the earlier circular-clamp configuration, use SL-520-022.

OEM Cross-References

• Turbo downpipe — GM: 12674630 / 12655717

OEM numbers are provided for identification only. This is a SPOOLOGIC replacement part.

⚠️ Not for Sale in California

This product is not CARB approved and is not legal for sale or use in California.

1-Year Limited Warranty

Every SPOOLOGIC turbo downpipe is covered by a 1-Year Limited Warranty against defects in materials and workmanship from the date of purchase. Warranty coverage requires that the downpipe first be shipped back to SPOOLOGIC for inspection. If SPOOLOGIC determines the failure was caused by a defect in materials or workmanship, the downpipe will be repaired or replaced at SPOOLOGIC’s discretion. Warranty does not cover damage from improper installation, over-torqued or mis-torqued flange hardware, cracked flanges from improper install sequence, damage from cutting, welding, or modification, heat wrap discoloration or degradation, EGTs beyond the downpipe’s rated operating range, tuning or fueling that exceeds safe exhaust gas temperatures, corrosion from road salt or contaminated environments, use outside the listed fitment, cosmetic wear, or normal heat cycling marks. Warranty does not cover labor, shipping, towing, downtime, gaskets, hardware, or any other costs outside the downpipe itself.