ARM Motorsports N55 CATTED DOWNPIPE - F3X - 4" EWG

The ARM 4" Catted Downpipe for BMW F-Series N55 vehicles is one of the most effective hardware upgrades available for increasing power, improving turbo spool, and enhancing exhaust sound. Designed for N55 models equipped with the 4" electronic wastegate (EWG) turbocharger, this downpipe delivers gains of up to 23whp and 29wtq while reducing backpressure and dramatically increasing exhaust flow.

The factory downpipe contains a restrictive catalyst that limits turbo efficiency. By replacing it with the ARM high-flow 200-cell sport catalyst, exhaust velocity increases, turbine response improves, and the vehicle becomes capable of safely running Stage 2+ tuning. Even on a completely stock exhaust system, the catted downpipe increases overall volume, sharpens burbles, and makes turbo spool more audible.

Constructed from mandrel-bent SS304 stainless steel, the downpipe starts at the turbo with a precision-machined 4" v-band flange, transitions into the high-flow catalyst, and tapers smoothly to match the OEM midpipe connection. Two O2 sensor bungs are positioned higher on the pipe to prevent wire tension during installation. A tune or CEL-delete solution is required to avoid check engine lights.

For drivers planning higher boost levels, this upgrade is essential. Most performance software already includes downpipe-required calibrations such as Stage 2 and E30 maps. Paired with an upgraded FMIC, many N55 vehicles reach approximately 400whp and 400wtq.

The ARM 4" Catted Downpipe is fully compatible with the OEM cat-back system as well as any aftermarket exhaust designed to fit the stock downpipe connection.

Fitment:
(Fits N55 engines with 4" EWG turbocharger only.)
• BMW F20 M135i – N55 3.0L
• BMW F20 M135i xDrive – N55 3.0L
• BMW F21 M135i – N55 3.0L
• BMW F21 M135i xDrive – N55 3.0L
• BMW F22 M235i – N55 3.0L
• BMW F23 M235i – N55 3.0L
• BMW F30 335i – N55 3.0L
• BMW F30 335i xDrive – N55 3.0L
• BMW F31 335i – N55 3.0L
• BMW F31 335i xDrive – N55 3.0L
• BMW F32 435i – N55 3.0L
• BMW F32 435i xDrive – N55 3.0L
• BMW F32 435i Gran Coupe – N55 3.0L
• BMW F33 435i – N55 3.0L
• BMW F33 435i xDrive – N55 3.0L
• BMW F34 335i – N55 3.0L
• BMW F34 335i xDrive – N55 3.0L
• BMW F34 335i Gran Coupe – N55 3.0L
• BMW F36 435i – N55 3.0L
• BMW F36 435i xDrive – N55 3.0L
• BMW F36 435i Gran Coupe – N55 3.0L
• BMW F87 M2 – N55 3.0L