BMW M3 G80 / M4 G82 / M2 G87 | Stainless Steel Downpipe (De-Cat)

BMW M3 G80 / M4 G82 / M2 G87 Stainless Steel Downpipe (De-Cat)

Engineered for BMW M3 G80, M4 G82, and M2 G87 owners, this Stainless Steel Downpipe is built catless (de-cat) to deliver maximum post-turbine exhaust gas flow on the S58 platform. Imported from leading manufacturers around the world and quality-controlled by BYC Performance, it bolts directly to the OEM v-band flange, no welding required.

The catless de-cat design minimizes post-turbine flow restriction, producing noticeably sharper high-RPM response across the S58's 473-543 hp (M3/M4) and 460 hp (M2 G87) output range. Because the de-cat downpipe will trigger a CEL, a supporting tune (software calibration) is required; this is the configuration of choice for track-focused and enthusiast drivers. For daily driving, choose the 200-cell catted variant.

Key Features

• Catless (De-Cat) Flow: Minimum post-turbine restriction, maximum hp and response gain.
• T304 Stainless Steel: Corrosion-resistant premium alloy, high-temperature rated.
• OEM V-Band Compatible: Bolts directly to factory flange, mates to mid-pipe or catback without modification.
• CNC-Bent Piping: Smooth internal surface, flow-optimized geometry.
• Turbine Flange Direct Fit: Matches S58 twin-turbo flange dimensions perfectly, leak-free.
• More Aggressive Exhaust Note: No catalyst restriction, fuller, more metallic high-RPM tone.
• Track-Oriented Design: Optimized for track-day and enthusiast use.

De-Cat vs. 200-Cell Catted Downpipe

This product is the catless (de-cat) variant:

• De-Cat (this product): Maximum flow, more aggressive sound, significant high-RPM response gain, but triggers CEL and requires a supporting tune
• 200-Cell Catted: Road use and inspection rules depend on your car and where you drive.
• For track, race, and tuned cars: de-cat preferred
• For daily driving: choose the 200-cell variant

Tune Requirement: Important

After fitting a de-cat downpipe, the OBD will read a lower lambda fault code and the CEL will illuminate. To resolve:

• A supporting tune (MHD, bootmod3, etc.) is used to disable the lower lambda
• The tune also extracts the maximum flow benefit from the downpipe
• De-cat is not recommended for street-legal inspection

Installation Notes

Downpipe replacement requires lift access and turbine bay work; professional installation is required. General steps:

1. Lift the vehicle and remove the underbody shield.
2. Loosen the stock downpipe turbine flange bolts (disconnect lambda sensors).
3. Release the mid-pipe v-band clamp and remove the stock downpipe.
4. Install the new downpipe to the turbine flange with a fresh gasket and torque to spec.
5. Refit the upper lambda sensors into the new downpipe bungs. The lower lambda bungs are disabled via the tune.
6. Tighten the mid-pipe v-band clamp (torque: 12 Nm).
7. Flash the tune file and run an OBD scan for fault codes.

Care & Maintenance

T304 stainless is corrosion-resistant and high-temperature rated. Re-check turbine flange torque after the first 500 km. Keep the tune calibration up to date.

FAQ

Does it require a tune?
Yes. The de-cat downpipe triggers a CEL, so a supporting tune (MHD, bootmod3, etc.) is required.

Does it fit the M2 G87?
Yes. The shared S58 engine makes this downpipe fully compatible with the BMW M2 G87 Coupe (2023+).

Compatible with M3 / M4 Competition and CS / CSL?
Yes. All trims share identical turbine flange geometry.

Compatible with previous-gen F80 / F82?
No. S55-powered F-generation models use a different turbine flange; this downpipe is S58-only (G80/G82/G87).

Inspection and road use?
The de-cat variant alters emissions values and is not suitable for inspection. For daily driving, choose the 200-cell catted variant.

Does it fit the M4 G83 Convertible?
Yes, fully compatible with the BMW M4 G83 Convertible (Cabriolet).

Shipping time?
In-stock items ship within 1-3 business days via partner couriers. Parts sourced to order are delivered within 30 days of the order date at the latest.

Warranty?
Manufacturing defects are covered by a 24-month BYC warranty, in addition to your legal rights.

Why BYC Performance?

BYC Performance is a Turkey-based performance tuning specialist sourcing premium parts from leading manufacturers around the world and supplying them to the Turkish market. Our catalog includes BMW M3 G80 de-cat downpipes, BMW M4 G82 catless downpipes, BMW M2 G87 downpipes, and many more high-quality S58 performance components.