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

3.5" N55 Downpipe Upgrade for 2012 – 2013.7 BMW M135i, M335i Flashark

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

Name: 3.5" N55 Downpipe Upgrade for 2012 – 2013.7 BMW M135i/335i/M2 F20/F21/F22/F30/F32/F33/F87
Brand: Flashark
SKU: FLJN-EXS22-00043002
Price: 266.0 USD
Availability: InStock
Rating: 5.0 (3 reviews)

SKU: FLJN-EXS22-00043002

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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

Year	Model	Chassis	Engine
2012–07/2013	BMW 135i / M135i	F20/F21	N55 3.0L
2012–07/2013	BMW 335i / 335i GT	F30/F34	N55 3.0L
2012–07/2013	BMW 435i	F32/F33/F36	N55 3.0L

Q: How do I know if I need the 3.5" or 4" N55 downpipe?

A: This is the single most important question before ordering. BMW used a 3.5-inch (90 mm) v-band flange on N55 engines with a Pneumatic Wastegate (PWG) built from 2012 through July 2013. Starting 08/2013, BMW switched to an Electronic Wastegate (EWG) with a 4-inch (102 mm) flange. The two flange sizes are NOT interchangeable. To verify: check the production date sticker on your driver's side door jamb. If your car was built 2012–07/2013, you need this 3.5" version. If built 08/2013 or later, you need the 4" EWG version.

Q: Will this fit my 2013 BMW 335i (F30)?

A: It depends on your exact production month. If your F30 335i was built between January 2012 and July 2013 (PWG N55 with 3.5" flange), this downpipe fits. If it was built August 2013 or later (EWG N55 with 4" flange), this downpipe will NOT fit — you need the 4-inch version. Check your door jamb production date sticker. The VIN production date can also be decoded — the 10th digit of your VIN indicates the model year, and BMW dealer tools can pinpoint the exact build month.

Q: Does this fit the BMW M2 (F87)?

A: This downpipe fits early-production M2 (F87) with the PWG N55 — specifically the 2016 model year M2s built before the mid-2016 switch to EWG. The M2 Competition (2018+, S55 engine) is NOT compatible. The later-production M2 (2017+ with EWG N55) requires the 4-inch downpipe version. Verify your M2's production date and wastegate type before ordering.

Q: Do I need a tune after installing this downpipe?

A: Yes, absolutely required. This is a catless downpipe — it removes the factory catalytic converter. Without a Stage 2 ECU tune, your BMW will trigger a check engine light (CEL) for catalyst efficiency below threshold. You need a tuning solution such as BM3 (Bootmod3) or MHD to disable the secondary O2 monitoring, clear the CEL, and retune fueling and boost targets for the increased exhaust flow. The tune is also what unlocks the full 15–25 WHP power gains — a downpipe without a tune leaves most of the potential untapped.

Q: Is this downpipe catted or catless?

A: Catless. This downpipe removes the factory catalytic converter entirely for maximum exhaust flow. It is designed for off-road, track, and competition use only. Street use on public roads may violate federal and state emissions laws — particularly in California and other emissions-controlled states. Check your local regulations before purchasing.

Q: How much horsepower will I gain?

A: With a proper Stage 2 ECU tune, expect 15–25 WHP and 20+ lb-ft of torque over a stock-downpipe tune on the PWG N55. The gains come from three sources: (1) the catless downpipe eliminates the largest exhaust restriction, allowing the turbo to breathe freely and spool faster, (2) the Stage 2 tune increases boost pressure and optimizes timing for the reduced backpressure, and (3) lower EGTs allow sustained peak output. Gains are most noticeable from 3,500 RPM to redline. Combine with an intake and cat-back for a full Stage 2 package delivering 40–60 WHP over stock.

Q: Can I install this myself?

A: Yes — this is a 100% bolt-on installation requiring no cutting or welding. Plan 2–4 hours. You'll need basic hand tools (metric sockets, ratchet with extensions, O2 sensor socket) and access to a lift or jack stands. Soak all factory exhaust fasteners in penetrating oil 24 hours before — BMW exhaust bolts seize with age. Key steps: disconnect O2 sensors, unbolt the factory downpipe from the turbo v-band and mid-pipe connection, install the Flashark pipe with the supplied gaskets and hardware, transfer the O2 sensors, and reassemble. Re-use the factory v-band clamp at the turbo housing if it's in good condition. Professional installation is recommended if you've never worked on a BMW exhaust.

Q: How does this compare to CP Racing or Vanguard downpipes?

A: CP Racing and Vanguard catless downpipes for the N55 PWG typically cost $500–$900+. They use comparable T304 stainless construction and similar 3.5-inch piping. The Flashark delivers the same fundamental benefit — unrestricted catless flow with pre-welded O2 bungs, TIG-welded T304 stainless steel, and complete hardware — at roughly one-third to one-half the price. The trade-off: CP Racing and Vanguard carry stronger brand recognition in the BMW tuning community and may offer longer warranty terms. Flashark includes a 1-year warranty and US-based email support. For a budget N55 Stage 2 build, the Flashark is the highest-value catless downpipe on the platform.

Q: Why T304 stainless steel — is it better than 201 stainless?

A: Yes, significantly. T304 stainless steel contains more chromium and nickel than 201, giving it superior corrosion resistance and heat tolerance — both critical for a turbo downpipe operating at extreme exhaust gas temperatures directly off the turbine housing. T304 is the industry standard material for quality turbo downpipes. 201 stainless is adequate for NA exhaust components but marginal for turbo downpipe conditions. Flashark uses T304 on this N55 downpipe because the turbo environment demands it.

Q: Will this pass emissions inspection?

A: No. This catless downpipe removes a federally mandated emissions control device. It will fail a visual inspection (missing catalytic converter), an OBD-II scan (catalyst efficiency codes), and a tailpipe sniffer test where applicable. This product is intended for off-road, competition, and track use only. If your state performs emissions testing (California, New York, Colorado, parts of Texas, etc.), do not install this downpipe on a street-registered vehicle.

Q: Do I need to upgrade anything else to get the most out of this downpipe?

A: The minimum requirement is a Stage 2 ECU tune (BM3/Bootmod3 or MHD). Beyond that, the recommended Stage 2 package for the PWG N55 includes: (1) catless downpipe (this part), (2) aftermarket intake (Eventuri, BM3 intake, or aFe Power), (3) cat-back or axle-back exhaust (Akrapovič, Remus, or MST), and (4) Stage 2 ECU flash. This full bolt-on package delivers 40–60 WHP over stock on the PWG N55. The next step beyond Stage 2 is a charge pipe upgrade and an intercooler — these become relevant at higher boost targets.

Q: What's your return policy and warranty coverage?

A: Flashark offers a 30-day return policy — if you're not satisfied, return the downpipe in unused, original condition for a full refund with no restocking fee. For installed products, contact our support team at support@flasharkracing.com and we'll work with you on a resolution. The downpipe is covered by a 1-year limited warranty against manufacturing defects including weld cracks, flange warping, and material corrosion. This warranty does not cover damage from improper installation, collision, or misuse. US-based email support is available for fitment questions, installation guidance, and warranty claims.