3.5" N55 Downpipe Upgrade for 2012 – 2013.7 BMW M135i/335i/M2 F20/F21/F22/F30/F32/F33/F87

Unlock the True Potential of Your N55

The N55 3.0L TwinPower Turbo is BMW's legendary inline-six — and the factory catalytic converter is the biggest bottleneck in the entire exhaust path. It chokes post-turbine flow, slows spool, raises EGTs, and caps your power ceiling. On the early PWG (Pneumatic Wastegate) N55 produced from 2012 through July 2013, the turbo outlet uses a 3.5-inch (90 mm) v-band flange — BMW switched to a 4-inch flange starting 08/2013 on the EWG (Electronic Wastegate) version. Verify your production date before ordering.

This Flashark 3.5-inch catless downpipe replaces the factory cat section with a straight-through mandrel-bent T304 stainless steel pipe, purpose-built for the PWG N55's turbo outlet geometry. The result: 15–25 WHP gains with a Stage 2 tune, faster turbo spool, sharper throttle response, and a deeper, more aggressive exhaust note — all without the cabin drone that ruins daily drivability.

This downpipe fits ONLY the 3.5-inch flange PWG N55 (production date 2012 through 07/2013). If your car was built 08/2013 or later with the EWG N55, you need the 4-inch version. Check your driver's side door jamb for the exact production month/year before ordering.

Key Features

3.5" (90 mm) V-Band Flange — PWG N55 Only — Precision-matched to the 3.5-inch turbo outlet on Pneumatic Wastegate N55 engines (2012–07/2013 production). This is NOT the 4-inch EWG version — verify your production date on the driver's door jamb before ordering

Catless Straight-Through Design — Eliminates the factory catalytic converter, the N55's single largest exhaust restriction. Unrestricted post-turbine flow means faster spool, lower EGTs, and measurable power gains above 3,000 RPM where the OEM cat chokes hardest

15–25 WHP Gains with Stage 2 Tune — Dyno-validated power increase when paired with a proper Stage 2 ECU flash (BM3/Bootmod3 or MHD). Catless downpipe + Stage 2 tune is the highest-ROI modification on the N55 platform

T304 Stainless Steel Construction — Grade 304 stainless provides superior heat resistance and corrosion protection compared to 201 stainless or aluminized steel. T304 is the industry standard for turbo downpipes operating at extreme EGTs directly off the turbine housing

TIG-Welded Seams — All joints are handcrafted TIG-welded for consistent penetration and leak-free sealing under boost. No weak spots, no porous welds, no cracking under thermal cycling

Mandrel-Bent Piping — Smooth radius bends maintain consistent inner diameter through every curve — no crush-bent restrictions, no turbulence pockets, zero flow bottlenecks from turbo flange to outlet

Pre-Welded O2 Sensor Bungs (Factory Position) — All factory O2 sensor bungs retained in their original locations and depths. Simply transfer the sensors from the stock downpipe — no drilling, no welding, no splicing

100% Bolt-On Installation — Direct replacement using OEM mounting points and flange patterns. No cutting, no welding, no permanent modification required. Compatible with both the stock cat-back and all aftermarket exhaust systems

Engineered for Quality

• 100% Bolt-On Installation: No cutting, welding, or permanent modification required. All factory O2 sensor bungs are retained in their original positions.

• Maximum Flow: The smooth mandrel-bent tubing ensures zero internal restrictions, unlike the crimped factory piping.

• Complete Hardware Kit: Every downpipe comes with the necessary gaskets and high-strength bolts to ensure a leak-free seal from day one.

Specifications

Material: T304 Stainless Steel

Piping Diameter: 3.5" (90 mm) mandrel-bent

Inlet Flange: 3.5" v-band (PWG N55 turbo outlet, production date 2012–07/2013)

Design: Catless straight-through (race/off-road)

Catalytic Converter: No — catless

O2 Sensor Bungs: Pre-welded (2×), factory position and depth

Construction: Handcrafted, TIG-welded joints

Surface Finish: Polished stainless steel

Fitment Type: 100% direct bolt-on (OEM mounting points)

Cat-Back Compatibility: Stock OEM and all aftermarket exhaust systems

Wastegate Type: PWG (Pneumatic Wastegate) only — NOT compatible with EWG (Electronic Wastegate)

Net Weight: ~5.5 kg

Estimated Install Time: 2–4 hours

Tuning Required: Yes — Stage 2 ECU tune required (BM3/Bootmod3 or MHD recommended)

Warranty: 1 Year

Pro Tip for BMW Owners:

To get the most out of this hardware and avoid a "Check Engine Light" (CEL), we highly recommend a Stage 2 ECU Flash (like Bootmod3 or MHD). This will calibrate your engine for the increased airflow and maximize your Horsepower gains!

What’s in the Box?

3.5" N55 High-Flow Downpipe