B909-C909 2018-2022 Ford Mustang GT Fastback 3in Catback Exhaust

Thermal R&D 3 Inch Catback Exhaust for the 2018-2022 Ford Mustang GT Fastback Without Active Valves

The Thermal R&D B909-C909 is a complete 3 inch catback exhaust system built specifically for the 2018-2022 Ford Mustang GT Fastback on vehicles without the factory Active Valve Performance Exhaust. Starting with 3 inch T304 stainless steel mandrel-bent tubing and adding a center straight-through muffler, the B909-C909 delivers a deep, aggressive V8 tone while incorporating True Helmholtz Technology to eliminate cabin drone at highway speeds. Dyno-tested to produce gains of 17 rear-wheel horsepower over stock, the system features brushed finish tubing, polished mufflers, and polished 4 inch quad angle-cut tips. Six specialized clamps are included for ease of installation and proper tip alignment. Adapters are also included for builds running performance headers. Manufactured from high-grade T304 stainless steel by Thermal Research and Development with a Limited Lifetime Warranty to the original vehicle owner.

Key Features

• 3 Inch T304 Stainless Steel Mandrel-Bent Tubing — Full 3 inch diameter for maximum flow and deep V8 tone
• True Helmholtz Technology — Cancels cabin drone at highway cruising speeds
• Polished 4 Inch Quad Angle-Cut Tips — Bold finish that complements the factory Mustang GT rear bumper
• Center Straight-Through Muffler — Maximum flow with aggressive sound character
• 17 RWHP Gain — Dyno-verified rear-wheel horsepower improvement over stock
• Brushed Finish Tubing and Polished Mufflers — Premium factory-plus appearance
• Fastback-Specific Fit — Does not fit convertible models
• Header Adapters Included — Ready for performance header fitment
• Limited Lifetime Warranty — To the original vehicle owner, non-transferable, excludes racing and commercial use
• Made in the USA — Manufactured in Lancaster, California

What's Included

• Complete 3 inch catback exhaust system
• Polished 4 inch quad angle-cut tips
• Six specialized clamps for proper alignment
• Header adapters for performance header compatibility
• Thermal R&D installation instructions

Specs

Fitment

Frequently Asked Questions

What is the difference between the B909-C909 and the B918-C918?
Both are 3 inch catback systems for the 2018-2023 Mustang GT Fastback. The B909-C909 is for vehicles WITHOUT the factory Active Valve Performance Exhaust. The B918-C918 is the newer generation system. If your Mustang has the factory active valve exhaust, do not use the B909-C909.

Does the B909-C909 fit my 2021 Ford Mustang GT Fastback without active valves?
Yes. The B909-C909 fits 2018-2022 Mustang GT Fastback models that are not equipped with the factory Active Valve Performance Exhaust system.

Will there be drone on the highway?
No. True Helmholtz Technology cancels the resonance frequencies that cause drone at 65 to 80 mph. Owners report deep, aggressive V8 tone under throttle with zero drone at highway cruising speeds.

How much horsepower does the B909-C909 add?
Thermal R&D dyno-tested the B909-C909 and measured a gain of 17 rear-wheel horsepower compared to the factory exhaust on the 2018+ Mustang GT 5.0L.

Does this require cutting or welding?
No. The B909-C909 is a bolt-on replacement. Six specialized clamps and all necessary hardware are included. No cutting, welding, or drilling is required.

Does this fit the Mustang GT convertible?
No. The B909-C909 is designed specifically for the Fastback body style only and does not fit convertible models due to differences in the exhaust tunnel and tip exit position.

Are adapters for performance headers included?
Yes. Header adapters are included for owners who plan to run performance headers, making the B909-C909 compatible with popular header upgrades.

What warranty does the B909-C909 carry?
Thermal R&D covers this system with a Limited Lifetime Warranty to the original vehicle owner, non-transferable. The warranty covers defects in materials and workmanship and does not apply to racing, commercial use, or improper installation. Manufactured in Lancaster, California.

Will the tips fit within the factory Mustang GT rear bumper?
Yes. The 4 inch quad angle-cut polished tips are positioned to fit cleanly within the factory 2018-2022 Mustang GT rear bumper cutouts without modification.

Installation Instructions

Apply penetrating fluid to all factory exhaust hangers and clamps prior to beginning the installation, especially on higher-mileage vehicles. With the vehicle safely raised on jack stands, unclip all rear hanger isolators and disconnect the stock catback at the catalytic converter outlet clamps. Remove the factory system. Install the B909-C909 mid-pipe first at the OEM catalytic converter outlets, leaving the six provided clamps hand-tight. Route the muffler and tip section, seating all hangers, and center the quad tips within the rear bumper cutouts before torquing all clamps to specification. Start the engine and inspect all joints for leaks. If you plan to run performance headers, use the included adapters at the header connection point.

WARNING: This product can expose you to chemicals including nickel compounds, which are known to the State of California to cause cancer and reproductive harm. For more information, go to www.p65warnings.ca.gov.