ARM Motorsports 4.5" Catless Downpipe
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The ARM 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 your downpipe unlocks power, improves turbo spool, allows you to safely run stage 2+ tuning, all while increasing the sound of your B58-powered BMW.

The ARM B58 Downpipe will increase the overall volume of your BMW, open up the exhaust burbles even on OEM programming, and make the turbo spool significantly more audible. The M240i in the video below is only equipped with the ARM B58 Downpipe, it is otherwise on a 100% stock exhaust. The car has never been flashed, it is on the original DME programming from BMW.

The ARM B58 Downpipe is built with SS304 stainless steel and backed by the ARM Motorsports Lifetime Warranty. The ARM B58 Downpipe starts with a 4.5" diameter precision CNC machined turbo v-band flange. The ARM B58 Downpipe then gradually reduces to a 3.1" diameter before the flex section. The flex section is incorporated into the ARM B58 Downpipe to relieve stress on the turbo during aggressive driving. The ARM B58 Downpipe is further secured by the 2-bolt bracket which utilizes the OEM downpipe mounting points. The 3.1" diameter continues after the flex section to allow for an easy installation to the OEM midpipe, or any midpipe that connects to the OEM B58 downpipe.

The ARM B58 Downpipe features two O2 sensor bungs to allow for reinstallation of the OEM oxygen sensors. The O2 sensor bungs are located closer to the turbo on the ARM downpipe to avoid stretching the O2 sensor wires during installation. A tune or CEL Delete will be required to avoid a check engine light from displaying on instrument panel.

By improving the exhaust flow on your B58 BMW with the ARM B58 Downpipe, you're prepared for the higher boost tunes. If you already have a software program for your B58 chances are these tune files are already pre-loaded into your software waiting for you to flash after your downpipe is installed. Most tunes require an upgraded downpipe to run properly.

Features:

• Increase Power and Torque
• Faster Turbo Spool
• Improved Exhaust Sound
• Safely Flash Stage 2+ Tunes
• SS304 Stainless Steel

What's Included:

• ARM Motorsports 4.5" Catless Downpipe