BMW Z4 M40i OPF Decat Downpipe with Heat Shield - B58
Unlock serious performance and sound with our BMW Z4 M40i OPF decat downpipe for the B58 engine, complete with an integrated heat shield. Manufactured from SS304 aircraft-grade stainless steel, TIG welded in-house and mandrel bent for maximum flow, this catless downpipe is designed to reduce backpressure, improve turbo spool and deliver a sharper throttle response. Expect a deeper, more aggressive exhaust note and a noticeable increase in power on OPF and PPF equipped B58 models.
Key features
- SS304 aircraft-grade stainless steel construction with premium TIG welds for strength and durability
- 4.5 inch stainless steel decat downpipe with a 3.5 inch section straight out of the turbo for optimal gas flow
- Integrated heat shield to help manage under-bonnet temperatures
- Mandrel-bent tubing for maximum internal diameter and superior flow without sacrificing mid-range torque
- Reduced exhaust backpressure and lower temperatures that aid turbocharger efficiency
- Noticeable power gains and a significantly more aggressive exhaust tone
- Substantial weight saving versus the factory catalytic converter
- Precisely engineered for OPF and PPF B58 applications for an excellent fit
Tested performance
We have tested this product and found increases of around 20 to 25 bhp, alongside faster spool and crisper throttle response. Our customers consistently report excellent fitment, a transformative sound and impressive performance gains.
Vehicle compatibility - B58 with OPF or PPF only
- BMW G20/G21 M340i 3.0L 285 kW / 374 PS 2019 OPF model
- BMW G22 440i 3.0L 285 kW / 387 PS 2019 OPF model
- BMW G30/G31 540i 3.0L 250 kW / 340 PS 2018 OPF model
- BMW G32 640i 3.0L 250 kW / 340 PS 2018 OPF model
- BMW G11/G12 740i 3.0L 240 kW / 326 PS 2019 OPF model
- BMW G14/G15/G16 840i 3.0L 250 kW / 340 PS 2019 OPF model
- BMW G29 Z4 M40i 3.0L 250 kW / 340 PS 2019 OPF model
- Toyota Supra MK5 A90 GR 3.0L 250 kW / 340 PS 2019 OPF model
OEM reference: Original BMW part number 18329897313.
Fitting and installation
Professional installation is recommended. We are happy to help with supply and fitment at Nforcd in Warwickshire. Request a quote via Sales@nforcd.com.
Important: please swap the gasket at the turbo end of the downpipe from your original unit. Not swapping the turbo-end gasket can cause a fuel smell in the cabin.
To help prevent an engine management light in most cases, we recommend adding a lambda sensor spacer (O2 spacer). You can find suitable spacers in our other items.
Why choose this B58 OPF decat downpipe
- Proven gains of around 20 to 25 bhp in our testing
- Enhanced turbo response and stronger mid-range pull
- Aggressive, motorsport-inspired exhaust sound
- High-quality SS304, TIG welded, mandrel bent for long-term reliability
- Heat shield included for better thermal management
- Excellent feedback on fitment and performance from Nforcd customers
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For motorsport and off-road use where local laws permit. OPF and emissions system modifications may not be road legal in your region.