BMW Z4 G29 M40i B58 4.5 inch Stainless Downpipe with 200 Cell Hi-Flow Sports Cat and Heat Shield
Unlock the full potential of your BMW B58 engine with this premium catted downpipe. Engineered for the BMW Z4 G29 M40i and wider B58 platform, this 4.5 inch stainless steel downpipe with a 200 cell hi-flow sports cat and integrated heat shield delivers faster turbo spool, sharper throttle response, stronger mid-range pull and a deeper, more aggressive exhaust note. Built from SS304 aircraft-grade stainless steel with smooth mandrel bends and TIG welded construction, it is a serious performance exhaust upgrade designed to reduce backpressure, lower exhaust gas temperatures and save weight compared to the factory catalytic converter.
We have fitted and tested this downpipe on our own and customer cars across the B58 range and consistently seen gains of around 20 to 25 bhp, with excellent drivability and response. Feedback from customers has been outstanding, with many praising the fitment quality and the way the car comes alive under boost.
Key features
- B58 downpipe for BMW Z4 G29 M40i with OPF PPF
- 4.5 inch SS304 aircraft-grade stainless steel for maximum durability and flow
- TIG welded and mandrel-bent tubing for optimal gas flow and strength
- 200 cell hi-flow sports catalytic converter for performance and emissions compliance
- Integrated heat shield to manage under-bonnet temperatures
- Faster turbo spool and sharper throttle response
- Noticeable power gains with a deep, aggressive exhaust tone
- Reduced backpressure and lower EGTs to relieve the turbocharger
- Maximised internal diameter maintains performance without sacrificing mid-range torque
- Significant weight saving versus the factory catalytic converter
Vehicle compatibility - OPF PPF models only
- BMW G20 G21 M340i 3.0L 285 kW 374 PS 2019 OPF
- BMW G22 440i 3.0L 285 kW 387 PS 2019 OPF
- BMW G30 G31 540i 3.0L 250 kW 340 PS 2018 OPF
- BMW G32 640i 3.0L 250 kW 340 PS 2018 OPF
- BMW G11 G12 740i 3.0L 240 kW 326 PS 2019 OPF
- BMW G14 G15 G16 840i 3.0L 250 kW 340 PS 2019 OPF
- BMW Z4 G29 M40i 3.0L 250 kW 340 PS 2019 OPF
- Toyota Supra MK5 A90 GR 3.0L 250 kW 340 PS 2019 OPF
Real-world results
We have tested this product and found increases of around 20 to 25 bhp, alongside noticeably quicker turbo response and improved mid-range punch. The exhaust note becomes sportier and more purposeful without being intrusive on a cruise.
Emissions and legality
Euro 5 rated sports cat that should pass an MOT emissions test when fitted. Road legal when used as intended.
Fitting and support
Professional installation is recommended, as factory exhaust tolerances can vary. Customer feedback notes the fit is very straightforward.
Prefer us to fit it for you? Nforcd offers installation in Warwickshire. Request a fitting quote at Sales@nforcd.com.
Why choose this B58 catted downpipe
- Proven performance on the BMW Z4 G29 M40i and wider BMW B58 platform
- Quality materials and construction for long-term reliability
- Better flow and reduced backpressure for cooler, more efficient running
- Heat shield included to protect surrounding components
- Excellent customer feedback on fitment and results
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