BMW 340i 440i 540i 740i B58 Decat Downpipe – 4.5 inch SS304 TIG Welded Performance Upgrade
Unlock serious performance and sound from your BMW B58 engine with our 4.5 inch stainless steel decat downpipe. Designed for the BMW M140i, M240i, 340i, 440i, 540i and 740i, this catless downpipe delivers faster turbo spool, sharper throttle response, reduced backpressure and a more aggressive exhaust note. Built from SS304 aircraft-grade stainless steel and TIG welded in house, it is a proven performance exhaust upgrade for B58-powered F and G series models.
We have tested this product and found increases of around 20 to 25 bhp. Customers consistently report excellent fitment, a noticeable improvement in drivability and a sound that transforms the car.
- 4.5 inch B58 decat downpipe made from SS304 aircraft-grade stainless steel
- TIG welded in house for strength, durability and a premium finish
- Mandrel-bent for maximum internal diameter and optimal gas flow
- Faster turbo spool and sharper throttle response
- Reduces exhaust backpressure and helps lower exhaust gas temperatures
- Noticeable power gains with a more aggressive, motorsport-inspired exhaust note
- Substantial weight saving versus the factory catalytic converter
- Direct-fit design for B58 turbo outlet with OEM-style connections
- Lifetime warranty for complete peace of mind
Important compatibility note: This will not fit 2018 onwards models equipped with a PPF/OPF unless it has been coded out and physically removed.
Vehicle compatibility – B58 engine only
- BMW M140i 2016+ F20 F21 and xDrive
- BMW M240i 2016+ F22 and xDrive
- BMW 340i 2016+ F30 F31 and xDrive
- BMW 440i 2016+ F32 F33 F36 and xDrive
- BMW 540i 2016+ G30 and xDrive
- BMW 740i 2016+ G11 G12 and xDrive
Installation and recommendations
- Professional installation is recommended. Tolerances can vary slightly between cars.
- You must swap the gasket at the turbo end of the downpipe. Failure to do so can cause a fuel smell in the cabin.
- We recommend a Lambda Sensor Spacer (O2 spacer) to help prevent a check engine light in most cases. Search our other items to add one to your basket.
- Need fitting? Choose Nforcd in Warwickshire. Request a fitting quote: Sales@nforcd.com.
Track use only: Decat downpipes are intended for off-road or track use where emissions compliance is not required.
Why choose this B58 decat downpipe
If you are searching for a BMW B58 decat downpipe, catless downpipe, 340i downpipe, 440i downpipe, 540i downpipe or 740i downpipe upgrade, this 4.5 inch SS304 TIG welded unit is the go-to choice for performance, reliability and sound. We use it ourselves and our customers love the fit, finish and results.