Description
3.5" High-Flow Turbo Downpipe for 2017-2023 Chevrolet/GMC 6.6L Duramax L5P Turbo Diesel
Replace the restrictive factory downpipe on your 2017-2023 Chevrolet Silverado or GMC Sierra 2500HD/3500HD with the 6.6L Duramax L5P Turbo Diesel using this mandrel-bent 3.5" downpipe. The OEM downpipe is one of the most restrictive components in the L5P exhaust system, featuring a pinched cross-section designed to clear the firewall that severely limits exhaust flow. Our 3.5" mandrel-bent downpipe eliminates this bottleneck for dramatically improved turbo response, lower EGTs, and increased power.
Why Upgrade Your L5P Downpipe?
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OEM Restriction: The factory L5P downpipe uses a flattened, ovalized design to clear chassis components – this creates significant backpressure right at the turbo outlet where flow matters most.
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True 3.5" Mandrel-Bent Flow: Our downpipe maintains full 3.5" internal diameter from the turbo V-band flange all the way to the exhaust connection – zero flow restriction.
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Lower EGTs: Free-flowing exhaust at the turbo outlet reduces exhaust gas temperatures by 50-150°F, critical for towing heavy loads up long grades.
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Faster Turbo Spool: Reducing backpressure allows the VGT turbocharger to spool faster, improving throttle response and reducing lag.
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Foundation for Future Upgrades: The stock downpipe becomes the limiting factor after any performance tuning. Our 3.5" downpipe supports 600+ HP builds.
Vehicle Compatibility
| Year |
Make |
Model |
Engine |
| 2017-2023 |
Chevrolet / GMC |
Silverado 2500HD / Sierra 2500HD |
6.6L Duramax L5P V8 Turbo Diesel |
| 2017-2023 |
Chevrolet / GMC |
Silverado 3500HD / Sierra 3500HD |
6.6L Duramax L5P V8 Turbo Diesel |
Premium Build Quality
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T409 Mandrel-Bent Stainless Steel: Consistent 3.5" diameter throughout – no crush bends, no diameter reduction, no flow restriction.
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V-Band Turbo Flange: Precision CNC-machined V-band flange ensures a perfect, leak-free seal at the turbocharger outlet.
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OEM Hanger Points: Pre-welded hanger brackets use factory exhaust hanger locations for true bolt-on installation.
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Corrosion-Resistant: T409 stainless offers excellent durability in all climates, road salt exposure, and under-hood heat cycling.
Performance Benefits
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+10-20 HP / +20-40 lb-ft Torque: Eliminating turbo outlet restriction frees significant power.
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50-150°F Lower EGTs: Critical for safe towing temperatures on long grades.
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Faster Turbo Spool: Immediate improvement in throttle response and reduced turbo lag.
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Deep Exhaust Tone: Fuller, deeper turbo diesel exhaust note.
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Supports High-HP Builds: Flows enough for 600+ HP with supporting modifications.
Installation Overview
This downpipe is designed for bolt-on installation using factory mounting points. The turbo-side connection uses a V-band clamp (included). Estimated installation time: 2-4 hours with basic hand tools, a floor jack or lift, and moderate mechanical experience. Access to the turbo outlet requires working from underneath the vehicle. No welding required.
Frequently Asked Questions
Q: Will this fit my 2022 Silverado 3500HD L5P?
A: Yes. This downpipe fits all 2017-2023 Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD models with the 6.6L Duramax L5P engine. All cab configurations (Regular, Double, Crew) and bed lengths are supported.
Q: Can I install this without a tune?
A: Yes. The downpipe itself does not require tuning and will not trigger a check engine light when installed on its own. However, for maximum performance benefit, a tune is recommended to optimize fuel and boost parameters for the increased exhaust flow.
Q: Do I need any special tools?
A: Standard hand tools plus a V-band clamp tool are helpful. Access to the turbo outlet requires working from underneath the truck – a lift or tall jack stands are recommended. Penetrating oil on the factory V-band clamp is essential.
Q: How does this compare to the factory downpipe?
A: The OEM downpipe is a flattened, oval design that necks down at multiple points, creating significant restriction. Our 3.5" mandrel-bent design maintains full diameter throughout, reducing backpressure by 30-50% at the turbo outlet.
Q: Will I hear a difference?
A: Yes. The 3.5" design produces a deeper, fuller exhaust tone with more pronounced turbo whistle at idle and under acceleration.
Q: Is this compatible with the factory exhaust system?
A: The downpipe connects at the turbo outlet (V-band) and to the factory exhaust or aftermarket system at the lower connection point. Fully compatible with OEM and most aftermarket exhausts.
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⚠️ Off-Road Use Only: This product is intended for off-road/competition use only. Not legal for highway use on emissions-controlled vehicles. Always check local and federal regulations before purchasing.
