The ARM 6" B58 Downpipe is one of the foundational upgrades for giving your B58-powered BMW more power, torque, and sound. The stock B58 downpipe comes from the factory with a catalyst that severely restricts exhaust flow, causing excessive backpressure with increased boost. Upgrading to the ARM 6" B58 Downpipe unlocks power, improves turbo spool, allows you to safely run stage 2+ tuning, all while improving the sound of your B58-powered BMW.

The ARM 6" B58 Catted Downpipe is perfect if you're looking for all of the performance of a Catless B58 Downpipe without the odor associated with increased emissions. Our B58 Catted Downpipe design incorporates a 6" high-flow 200 cell ceramic catalytic converter, making it a standout choice for those seeking power without while reducing emissions. The increased volume and improved turbo spool that from the catless variations are still present in our 6" B58 Catted Downpipe.

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The ARM 6" Catted B58 Downpipe replaces the restrictive factory downpipe with a 200 cell catalyst with a 6" diameter that significantly improves exhaust flow. This upgrade unlocks additional power and torque while reducing emissions compared to a full catless B58 downpipe, allowing you to safely run Stage 2+ tunes and enjoy a more vibrant sound from your B58-powered BMW.

Highlights

• 6" 200 Cell High-Flow Catalyst
•  Improved Exhaust Sound
• Faster Turbo Spool
• Stage 2+ Tune Compatibility

ENHANCE THE SOUND OF YOUR B58

The ARM 6" B58 Catted Downpipe amplifies the overall volume of your B58's exhaust, bringing out the burbles and enhancing the audible presence of the turbo spool, even on the OEM tune.  Below is a sound clip of the ARM 6" Catless Downpipe, paired with our B58 Midpipe, and Single Exit Exhaust. 

CONSTRUCTION

The ARM 6" B58 Catted Downpipe starts with a 4.5" diameter precision CNC machined turbo V-band flange which matches up perfectly to the OEM turbo or upgraded turbo with an OEM flange.  It then rapidly transitions to the 6" OD high-flow catted section. 

The ARM 6" B58 Catted Downpipe features two O2 sensor bungs to allow for reinstallation of the OEM oxygen sensors.  The pre-catalyst O2 sensor bung is located closer to the turbo on the ARM 6" B58 Downpipe to avoid stretching the O2 sensor wires during installation.  The post-catalyst O2 sensor bung comes with a built-in extension to allow the sensor to reach around the 6" section of the downpipe.  

The ARM 6" B58 Downpipe then reduces to the OEM size to allow it to connect to the OEM midpipe or the ARM B58 Midpipe Upgrade.  The flex section is incorporated into the ARM 6" B58 Downpipe to relieve stress on the turbo during aggressive driving.

The ARM 6" B58 Downpipe is further secured by the 2-bolt bracket which utilizes the OEM downpipe mounting points.

Fitment

• 2019+ G20, G22 & G26 BMW M340i & M440i & xDrive
• 2019+ F22 BMW M240i & xDrive
• 2021+ G42 BMW M240i & xDrive
• 2019+ G05 BMW X5 40i & xDrive
• 2019+ G29 BMW Z4 M40i
• 2019+ G14/G15/G16 840i & xDrive
• 2019+ G14/G15/G16 840i & xDrive
• 2016+ F22/F23 BMW M240i & M240i xDrive
• 2016+ F30/F31 BMW 340i & 340i xDrive
• 2016+ F32/F33/F36 BMW 440i & 440i xDrive
• 2016+ G30 BMW 540i & 540i xDrive
• 2016+ G32 GT BMW 640i & 640i xDrive
• 2016+ G11/G12 BMW 740i & 740i xDrive
• 2020+ Supra A90/A91 3.0T

Every ARM Motorsports product is backed by a lifetime warranty which is automatically issued at the time of purchase. Your warranty protects you against any defects in craftsmanship or fitment. The warranty entitles you to a replacement unit.