4-Inch Stainless Steel Downpipe

The ARM Motorsports N55 Downpipe is a critical hardware upgrade for N55-powered F-Series BMWs seeking to maximize performance. The stock downpipe features a catalyst that significantly restricts exhaust flow, hindering power output. This 4-inch diameter downpipe from ARM Motorsports liberates exhaust gases, resulting in enhanced turbo spool, a more audible exhaust note, and the capability to run Stage 2+ tuning. It's considered the first essential hardware upgrade for any N55 owner looking to unlock the full potential of their engine. Constructed from mandrel-bent SS304 stainless steel, this downpipe is built for durability and backed by ARM Motorsports' Lifetime Warranty. The design begins with a 4-inch diameter at the turbo v-band connection, smoothly transitioning to a flared joint that matches the stock midpipe's v-band connection for an optimized flow path. Two O2 sensor bungs are integrated to allow for the reinstallation of factory oxygen sensors, positioned higher on the downpipe to prevent strain on the wiring during installation. A tune or CEL delete is necessary to prevent a check engine light. By improving exhaust flow, this downpipe prepares your F-Series BMW for higher boost tunes, often pre-loaded in existing software. Most performance tunes require an upgraded downpipe and potentially a Front Mount Intercooler (FMIC) to function optimally. When paired with appropriate tuning, Stage 2 N55 engines can achieve approximately 400 wheel horsepower and 400 wheel torque. The downpipe also contributes significantly to the exhaust's sound, increasing volume and turbo audibility, even with stock exhaust systems. It is compatible with aftermarket exhausts designed to connect to the stock N55 downpipe. The ARM F-Series N55 Downpipe is specifically designed for vehicles equipped with a 4-inch EWG Turbocharger. Fitment includes various BMW models such as the F20 M135i/M135i xDrive, F22/F23 M235i, F30/F31/F34 335i/335i xDrive, F32/F33/F36 435i/435i xDrive, and the F87 M2, all powered by the N55 3.0L engine. This product is intended for Off-Road Use Only and is illegal to use on public roads in most jurisdictions.