5″ GM Duramax 6.6L L5P 2500 3500 2017-2023 Race Exhaust (4-BOLT Flange)

Here’s the complete technical breakdown for the 5″ L5P Duramax Race Exhaust (4-Bolt Flange) for 2017-2023 HD trucks:

Critical Identification: 4-Bolt Flange System

🔍 Verify Your Connection Type

• 2017-2023 L5P uses one of two turbo connections:

  • Early L5P (2017-2019 Mid): 3-bolt triangular flange

  • Late L5P (2019+-2023): 4-bolt square flange (this kit)

• Visual Check:

  • 4-bolt = Square flange with evenly spaced bolts

  • 3-bolt = Triangular pattern

System Specifications

✅ Diameter: 5″ mandrel-bent (30% more flow than stock)
✅ Deletes: DPF + DOC (Catalyst) – Off-road only
✅ Flange Type: Laser-cut 4-bolt with reinforced gasket
✅ Material Options:

• T409 Stainless (most common)

• T304 Stainless (premium corrosion resistance)
  ✅ Hardware Included:

• Grade-8 flange bolts

• OEM-style donut gasket

• V-band clamp for mid-pipe connection

Performance Gains (With Tuning)

• Turbo Spool: 300-400 RPM sooner

• EGT Reduction: 150-200°F under load

• Power Potential: +25-50HP (when tuned)

• Sound: Aggressive turbo whistle + deep tone (no muffler)

Installation Requirements

🔧 Tools Needed:

• 13mm & 15mm sockets

• Torque wrench (55 lb-ft for flange bolts)

• Exhaust hanger pliers

⚠️ Critical Steps:

1. Disconnect Batteries (prevents ECM damage)

2. Retain Sensors:

   • Exhaust Backpressure (EBP) sensor

   • All temperature probes

3. Apply Nickel Anti-Seize to flange bolts

Tuning Requirements

🚨 Immediate Tuning Necessary – Without:

• Limp mode in <50 miles

• Regen attempts will continue

Recommended Tuners:

• MM3 (EcoFlash) – Full DPF/DEF delete

• PPEI L5P Suite – Smoothest power delivery

• Duramaxtuner – Towing-optimized maps

Legal & Warranty Consequences

Supporting Upgrades

1. EGR Delete Kit (Recommended for tuned trucks)

2. S&B Cold Air Intake (+12-15HP)

3. Banks iDash Gauges (Monitor EGT/Boost)