Downpipe Exhaust For BMW 3 series M3, 4 series M4 - S55 Engines | SPELAB

Who This Is For

2015-2020 BMW M3 (F80) and M4 (F82/F83) owners with the S55 twin-turbo inline-6 who want a 3" high-flow catless downpipe for quicker turbo spool, stronger top-end power, and a deeper M exhaust note.

Key Features

• 3" diameter for maximum exhaust flow
• Stainless steel construction with mirror-polish finish
• Direct bolt-on replacement for factory downpipes
• Sharpens turbo response and increases top-end power
• Unlocks a deeper, more aggressive M exhaust note

Product Specifications

• Engine: BMW S55 3.0L Twin-Turbo
• Pipe Diameter: 3 inch
• Material: Stainless Steel
• Finish: Mirror Polish
• Configuration: Catless
• Flange Type: V-Band
• Weight: 4.92 kg (4920 g)

What's Included

• Downpipe (pair — twin-turbo)
• Mounting hardware

Check Before Choosing

• CEL behavior: A catless S55 downpipe triggers catalyst-efficiency CEL codes. Suppress them with a Bootmod3, MHD, or JB4 Stage 2 tune.
• Tune required: Yes — a Stage 2 tune is required to suppress the CEL and unlock the full power gain.
• M2 Competition (F87): The M2C (F87) shares the S55 engine but has a different underbody. Verify fitment before ordering.
• Street legality: No — off-road / race use only under the Clean Air Act.

Vehicle Fitment

Compatible vehicles: BMW M3, BMW M4 Coupe, and BMW M4 Convertible (2015–2020).

Installation Guide

Pre-Installation Checklist

• Confirm your engine code and model year match the fitment list above
• New gaskets and mounting hardware ready
• 22mm slotted O2 sensor socket + PB Blaster on hand
• a Stage 2 tune (Bootmod3 / MHD / JB4) to clear CEL

Installation Steps

1. Lift the vehicle and secure it on jack stands
2. Soak the O2 sensors and flange bolts with PB Blaster for 30+ minutes
3. Unplug and remove the O2 sensors with the slotted socket
4. Remove the factory downpipe and discard the old gasket
5. Bolt on the new downpipe with a fresh gasket
6. Reinstall and reconnect the O2 sensors
7. Flash your tune to suppress the check engine light

Installation Notes

• Never reuse the old gasket — it will cause an exhaust leak
• Use a slotted O2 socket, not a wrench — the sensor threads strip easily
• A catless downpipe triggers a CEL until the ECU is tuned
• Expect a stronger raw exhaust smell (normal for catless)

FAQ

Is this catted or catless?

Catless.

How much power will I gain on the S55?

The S55 responds strongly to a catless downpipe — expect noticeably quicker turbo spool and stronger top-end power. A Stage 2 tune is required.

Does it fit the M2 Competition?

The M2C (F87) shares the S55 engine but has a different underbody. Verify fitment before ordering.

Is it street-legal?

No — off-road / race use only under the Clean Air Act.