L5P Downpipe 3.5 Inch Turbo Direct Pipe | 2017-2026 GMC Chevrolet

Introduction

This L5P downpipe is a 3.5' turbo direct downpipe made for 2017-2026 GM Duramax 6.6L L5P pickup trucks. It bolts directly to the turbocharger and replaces the factory downpipe that contains the DOC (Diesel Oxidation Catalyst) filter.

Removing the DOC right after the turbo allows exhaust gases to flow out faster. This helps the turbo spool quicker, reduces exhaust restriction and improves overall engine performance. This downpipe is commonly used on off-road and competition trucks where maximum exhaust flow is needed.

Technical Specifications

Vehicle Fitment

Why an L5P Downpipe Replaces the Factory DOC

On GM L5P Duramax engines, the DOC is positioned immediately after the turbocharger. While necessary for emissions compliance, it creates a major restriction in the exhaust path. Installing an aftermarket L5P downpipe is the primary method to remove this restriction at its source.

A larger 3.5' Duramax down pipe allows exhaust gases to exit the turbo more efficiently, reducing backpressure while improving throttle response, turbo sound and engine efficiency. This modification is commonly performed as part of a complete L5P delete exhaust system intended for off-road or competition use.

Because the DOC is an emissions-controlled component, professional custom tuning is required after installation to prevent check engine lights and ensure proper engine operation. This product is not emissions compliant and is not legal for street-driven vehicles.

L5P Downpipe Features

• 3.5' stainless steel L5P turbo downpipe
• Approximately 20% improved exhaust flow over the factory Duramax down pipe
• Completely removes the factory L5P DOC
• Heat wrap included to reduce engine bay temperatures
• Improved heat retention for stronger exhaust velocity
• 4-bolt turbo flange with two pre-installed studs
• Built for maximum flow in off-road and competition applications
• 2020+ trucks may require minor hanger adjustment

Benefits

• Reduced exhaust restriction directly at the turbocharger
• Improved turbo response and throttle feel
• Lower exhaust backpressure under towing or heavy load
• Supports higher horsepower and torque with proper tuning
• Enhanced turbo sound compared to the stock L5P downpipe

Installation & Notes

• Bolt-on installation at the turbocharger using the factory mounting location
• Basic hand tools required
• Designed to work with DPF delete pipes and full exhaust systems
• Custom tuning required
• For off-road and competition use only

Frequently Asked Questions (FAQ)