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

The ARM 6" B58 Downpipe is the largest catless downpipe available for the B58 platform — and the sound will astonish you. The stock downpipe's catalyst severely restricts exhaust flow and builds excessive back-pressure as boost rises. Upgrading unlocks power, improves turbo spool, lets you safely run Stage 2+ tuning and deepens the note of your B58-powered BMW.

Highlights

• 6" high-flow section — the largest available for the B58.
• Improved exhaust sound and louder burbles, even on OEM programming.
• Faster turbo spool; safely flash Stage 2+ tunes.
• SS304 stainless steel, TIG-welded.

Construction

Starts with a 4.5" precision CNC-machined turbo V-band flange that rapidly transitions to the 6" OD high-flow section, then reduces to the OEM 3.1" diameter to connect to the OEM or ARM B58 midpipe. Two O2 sensor bungs retain the factory sensors — the pre-cat bung sits closer to the turbo to avoid stretching wires, and the post-cat bung has a built-in extension to reach around the 6" section. A flex section relieves turbo stress, and a 2-bolt bracket uses 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, G05 X5 40i (incl. xDrive); Toyota A90 & A91 Supra.

What's included: ARM 6" B58 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.