Wagner Tuning BMW F-Series N55 Sport Cat Downpipe Kit -6/13

Wagner Tuning BMW F-Series N55 Sport Cat Downpipe Kit (Up to 06/2013)

This downpipe kit from Wagner Tuning is a direct replacement for the standard downpipe on BMW’s N55 turbocharged engine. It pairs a larger-diameter pipe with a high-flow sports catalytic converter to reduce exhaust back pressure – the resistance that slows down exhaust gases leaving the engine. The result is improved exhaust flow, which helps the turbo work more efficiently and allows the engine to produce more power and torque.

It’s a well-engineered upgrade for owners of the BMW M135i, 335i, or 435i who want to get more from their car without making dramatic changes to the rest of the drivetrain.

What’s Included and How It’s Built

The kit centres around a 76mm diameter downpipe – wider than the factory item – made from 1.4301 grade stainless steel (also known as SS304), which is resistant to corrosion and built to handle the high temperatures found close to the turbocharger. The pipe is CAD-designed (engineered digitally to ensure precise, accurate fitment) and is intended to replace the original BMW part number 18328603875 with no additional modification needed.

The sports catalytic converter uses a 200 CPSI cell density. CPSI stands for cells per square inch – a lower number than the standard OEM catalyst means less restriction, better gas flow, and improved performance, while still maintaining catalytic function. The connection diameter at the rear of the kit measures 105mm for a clean, secure join to the rest of the exhaust system.

Two lambda probe connections are included (lambda probes are the sensors that measure exhaust gas composition), making the kit compatible with various sensor configurations found across the supported model range.

Performance Benefits

• Reduced exhaust back pressure for improved turbo efficiency and power delivery
• Noticeable gains in torque, particularly in the mid-range
• Less heat build-up around the turbocharger compared to the more restrictive standard pipe
• Direct OEM replacement fitment – no cutting, welding, or major modifications required
• Durable stainless steel construction for long-term reliability

Technical Specifications

Vehicle Fitment

This kit is designed for BMW F-Series models fitted with the N55 engine, built up to June 2013 (6/13). Specifically, this covers the M135i(x) F20/F21, the 335i(x) F30/F31/F34, and the 435i(x) F32/F33. Please use the vehicle lookup tool on this page or check the Vehicle Fitment tab to confirm compatibility with your specific car before purchasing.

Please note: an error display in the DME (the engine management system) is possible following installation of this downpipe. This is a known characteristic and may require attention from a specialist, typically through a software adjustment.

Important Notice Regarding Catalytic Converter Use and Warranty

Wagner Tuning sport catalytic converters are designed for motorsport and off-road use. Fitment of this product may affect your vehicle’s road legality and emissions compliance, depending on the regulations in your country or region. It is the buyer’s responsibility to ensure the product is used in accordance with local laws.

Installation of this kit may also affect the manufacturer warranty on related drivetrain or emissions components. If you are unsure, consult a qualified specialist before fitting.