BMW 3 Series G20 / 4 Series G22 B48 | Heat-Shielded Stainless Steel De-cat Downpipe

BMW 3 Series G20 / 4 Series G22 B48 Heat-Shielded Stainless Steel Downpipe (De-cat)

Engineered for BMW 3 Series G20 (Sedan, 2019+) and BMW 4 Series G22 (Coupé, 2020+) with the B48 1.6L or 2.0L turbo engine, this Heat-Shielded Stainless Steel De-cat Downpipe completely removes the catalyst restriction at the turbo outlet for maximum airflow and the most aggressive exhaust note. This track/race-focused variant is designed to be paired with an ECU tune. Imported from leading manufacturers around the world and quality-controlled by BYC Performance, the system bolts directly to the OEM downpipe v-band.

Heat-wrap insulation lowers engine bay temperatures, keeps intake air cooler, and sharpens turbo response. The B48 engine character gains a deeply metallic and aggressive exhaust note: built for 320i/330i/420i/430i owners chasing maximum performance via tune or preparing for the track.

Key Features

• De-cat (Catless) Design: No catalyst restriction, maximum exhaust flow and highest power potential.
• Heat Wrap Insulation: Reduces engine bay temperatures, keeps intake air cooler, sharpens turbo response.
• T304 Stainless Steel: Corrosion-resistant premium alloy, rated for post-turbo temperatures.
• CNC-Bent Piping: Smooth internal surface, flow-optimized geometry.
• OEM V-Band Fitment: Direct bolt-on to factory turbo flange and catback v-band. No welding required.
• O2 Sensor Bung: OEM lambda sensor installs directly; ECU tune required to clear CEL.
• Stock Catback Compatible: Works with both the OEM catback and aftermarket valvetronic catback systems.

De-cat vs. 200 Cell Catalyst: This Is De-cat

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

• De-cat (this product): Maximum flow, most aggressive sound, highest power potential. Triggers CEL (check engine light): requires ECU tune to suppress. Fails emissions inspection.
• 200 Cell Catalyst (separate SKU): Usually no tune required. Road use and inspection rules depend on your car and where you drive.
• For daily driving: 200 cell preferred
• For track/race + tune: de-cat preferred (this product)

Installation Notes

De-cat downpipe replacement requires access under the turbo and professional installation. General procedure:

1. Lift the vehicle and remove the underbody skid plate.
2. Carefully unscrew the OEM lambda (O2) sensor.
3. Loosen the turbo outlet flange bolts and the catback v-band clamp.
4. Carefully lower the OEM downpipe.
5. Attach the new de-cat downpipe to the turbo flange (torque: 22 Nm).
6. Tighten the catback v-band clamp (12 Nm).
7. Install the O2 sensor into the new bung.
8. Apply an ECU tune: mandatory to clear CEL and optimize air-fuel mixture.
9. Check for leaks then perform a test drive.

Care & Maintenance

T304 stainless is corrosion-resistant. Heat wrap insulation may emit slight smoke during first warm-up. This is normal. Re-check turbo flange and v-band clamp torque after first 500 km. Avoid pressure-washing the heat wrap directly.

FAQ

Will the de-cat downpipe trigger CEL (check engine light)?
Yes. Without a catalyst the secondary lambda sensor throws a fault and triggers CEL. ECU tune is required to clear it.

Does it require a tune (ECU software)?
Yes. The de-cat variant requires a tune to suppress CEL and optimize the air-fuel mixture.

Does it pass TÜV / vehicle inspection?
No. Without a catalyst it fails emissions inspection. This product is intended for track/race use.

Is it compatible with BMW M3 G80 or M4 G82?
No. M3 G80 / M4 G82 / M2 G87 use the S58 inline-six engine with a completely different turbo flange and downpipe geometry. This downpipe is for B48-engined G20/G22 only.

Is it compatible with M340i or M440i?
No. M340i and M440i use the B58 inline-six engine; a separate downpipe SKU is required.

Will it work with the stock catback?
Yes. OEM v-band flange is preserved, compatible with both stock catback and aftermarket valvetronic catback.

Shipping time?
In-stock items ship within 1-3 business days via partner couriers. International shipping available. 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 G20 downpipes, G22 B48 de-cat exhausts, 330i track downpipes, and many more high-quality performance components. All parts are built with motorsport-grade materials and undergo strict quality control.