6" B58 CATTED DOWNPIPE - 240i 340i 440i 540i 640i 740i

The ARM 6" B58 Catted Downpipe gives you the performance of a catless B58 downpipe without the odor of increased emissions. It uses a 6" high-flow 200-cell ceramic catalyst to significantly improve exhaust flow over the restrictive factory downpipe — unlocking power and torque, letting you safely run Stage 2+ tunes, and bringing out a more vibrant B58 sound, while keeping emissions in check.

Highlights

• 6" 200-cell high-flow catalyst.
• Improved exhaust sound and louder burbles, even on the OEM tune.
• Faster turbo spool.
• Stage 2+ tune compatibility.

Construction

Starts with a 4.5" precision CNC-machined turbo V-band flange (matches the OEM turbo or upgraded turbos with an OEM flange), then transitions rapidly to the 6" OD high-flow catted section. Two O2 sensor bungs retain the factory sensors — the pre-cat bung sits closer to the turbo to avoid stretching wires, the post-cat bung has a built-in extension to reach around the 6" section. It reduces to OEM size to connect to the OEM or ARM B58 midpipe, with a flex section to relieve turbo stress and a 2-bolt bracket using the OEM mounting points.

Fitment (B58 3.0L)

BMW F22/F23 M240i, F30/F34 340i, F32/F33/F36 440i, G30 540i, G32 640i, G12 740i, G15 840i (incl. xDrive); Toyota A90 & A91 Supra.

What's included: ARM 6" B58 catted downpipe.

Backed by ARM Motorsports' lifetime warranty against defects in craftsmanship and fitment.

Emissions disclaimer: This product is intended for off-road, race, or closed-course competition use only and is not legal for use on pollution-controlled vehicles operated on public roads in most states and provinces. You are responsible for compliance with all applicable emissions laws. Please check your local laws before purchase and installation.

Ships from our Vancouver shop — KORE SPEED is proudly Canadian-owned, with no surprise cross-border duties for Canadian buyers. Questions on fitment? Email support@korespeed.com.