Flowmaster’s “Active” American Thunder Exhaust Brings S550s to Life

Flowmaster exhausts may be synonymous with Fox-body Mustangs in many minds (let’s be honest — there’s just something about a street Fox with “Flowmasters”), but the brand is constantly evolving and bringing new applications and products to the market. Your 2018-2020 Mustang GT can now roar to life (or keep quiet) with Flowmaster’s American Thunder Axle-Back Exhaust System with Active Valves (PN: 817859).

When the box arrives on your doorstep, you’ll have everything you need for a painless at-home installation.

The new exhaust system features what Flowmaster calls its W.A.V.E. Technology. That’s short for Wireless Active Valve Exhaust. The system comes with two wireless remotes that control the exhaust’s actuators and exhaust valves, and the system’s specially designed mufflers feature Flowmaster’s “Outlaw” technology. When those valves are closed, the Mustang will emit a moderate exterior and interior tone. But when they’re open? That’s when the fun begins. All one must do is push the remote causing the valves to open, allowing the Mustang to roar to life. Do yourself a favor and watch the video above to hear the before and after-installation difference.

The exhaust system itself is built from 3-inch mandrel-bent 16-gauge 409S stainless steel tubing for high flow and durability, and features quad tips built from 4-inch polished 304 stainless steel. All parts and hardware needed for installation are included in the kit, and detailed instructions allow for easy at-home installation, utilizing factory hanger locations. It is protected by the Flowmaster Lifetime Limited Warranty.

This system fits all 2018-2020 Mustang GT coupes and convertibles without the Factory Active Performance Exhaust option.

Article Sources

About the author

Stephanie Davies-Bardekoff

Stephanie Davies-Bardekoff got her start in automotive media while attending Rutgers. She worked for Roush Performance for a while, before eventually landing here at Power Automedia. Her Coyote-swapped 1992 Fox-body drag car is her prized possession.
Read My Articles

Blue Oval Muscle in your inbox.

Build your own custom newsletter with the content you love from FordMuscle, directly to your inbox, absolutely FREE!

Free WordPress Themes
FordMuscle NEWSLETTER - SIGN UP FREE!

We will safeguard your e-mail and only send content you request.

Ford Muscle - The Ultimate Ford Mustang Magazine

We'll send you the most interesting FordMuscle articles, news, car features, and videos every week.

Ford Muscle - The Ultimate Ford Mustang Magazine

FordMuscle NEWSLETTER - SIGN UP FREE!

We will safeguard your e-mail and only send content you request.

Ford Muscle - The Ultimate Ford Mustang Magazine

Thank you for your subscription.

Subscribe to more FREE Online Magazines!

We think you might like...



Muscle Car & Hot Rods

Drag Racing

Ford Muscle - The Ultimate Ford Mustang Magazine

Thank you for your subscription.

Subscribe to more FREE Online Magazines!

We think you might like...

  • Next-Gen Ford Performance
  • Muscle Car & Hot Rods
  • Drag Racing

Ford Muscle - The Ultimate Ford Mustang Magazine

Thank you for your subscription.

Thank you for your subscription.

Ford Muscle - The Ultimate Ford Mustang Magazine

Thank you for your subscription.

Thank you for your subscription.

Loading