The right B58 downpipe depends first on which generation of B58 your BMW has. Gen 1 and Gen 2 cars (roughly 2016 to 2024, depending on model) share a downpipe layout with several brands, while the newer Gen 3 B58TU2 uses its own part. After you know your generation, the choice comes down to pipe diameter (4, 4.5, 5 or 6 inch), catless or catted, and whether your tune is ready for it.
This guide covers which cars have which B58, why the generations do not swap, how to read the sizes, and what to plan alongside the downpipe.
Which B58 Does Your Car Have?
BMW has used the 3.0 litre turbocharged B58 inline-six across a long list of cars since 2016. The fitment lists in our listings group them like this:
| Generation | Examples from the listings |
|---|---|
| Gen 1 | F20 M140i, F22/F23 M240i, F30/F31 340i, F32/F33/F36 440i, early G30 540i, G11/G12 740i, G01 X3 M40i |
| Gen 2 | G20/G21 M340i (2020–2024), G22/G23/G26 M440i, G42 M240i, G05 X5 40i, G06 X6 40i, G07 X7 40i, G14/G15/G16 840i |
| Gen 3 (B58TU2) | 2025+ G20/G21 LCI M340i, 2025+ G22/G23/G26 LCI M440i, 2024+ G60/G61 540i, G70 740i, 2025+ G45 X3 M50, 2023+ X5/X6/X7 LCI 40i |
The Toyota GR Supra also uses the B58, and some BMW downpipes list it in their fitment. Model years overlap at the changeovers, and some cars received updates mid-cycle. The safest way to confirm is your VIN. The Spool Gen 3 listing, for example, says it cannot guarantee fitment on every 2025 car and asks owners to check the parts diagram first. Do the same for any B58 part.
Why the Generations Are Not Interchangeable
The generations differ in their turbo and exhaust hardware, and brands design their pipes around those differences. That is why IRL lists separate MaxFlow downpipes for the F30 340i, the G-series Gen 2 and the Gen 3. Other brands, such as Palenon and Rvng, build one pipe that covers both Gen 1 and Gen 2 cars, then a separate pipe for Gen 3. Read the fitment list on the listing, not just the engine code in the title.
OPF and Non-OPF Cars
Some B58 cars, depending on market and year, have a gasoline particulate filter (OPF or GPF) in the exhaust. It is a separate part from the downpipe converter and affects which mid-pipe and tune setup the car needs. If your car has one, ask your tuner how they handle it before choosing a downpipe, and confirm the listing covers your exact car.
4 Inch vs 4.5 Inch vs 5 Inch vs 6 Inch
B58 downpipes are sold in several diameters. Bigger pipes have more flow area, and the listings describe the same goal: keep the diameter large right after the turbo, where pressure is highest, instead of necking down early.
- 4 inch: the Spool Gen 3 race pipe keeps a consistent 4 inch diameter with a machined v-band transition.
- 4.5 inch: Palenon's V1 and V2 Gen 1/Gen 2 pipes and Spool's 4.5 inch race pipe sit in the middle of the range and work with factory and aftermarket exhausts.
- 5 inch: Palenon's 5 inch Gen 1/Gen 2 pipe steps from 4.5 to 5 to 4 inch before meeting the factory connection; Rvng and Spool also offer 5 inch designs. Spool says the larger size gives a deeper tone.
- 6 inch: Rvng's XL Flow pipe for the Gen 3 B58TU2 has the largest inlet in their range, aimed at higher-power builds.
For a stock-turbo car with a tune, any of these will reduce backpressure compared with the factory part. The very large sizes make the most sense on higher-power or upgraded-turbo builds.
Catted vs Race Options
Most B58 pipes are race (catless) designs. Some are offered with a converter: the IRL Gen 2 and Gen 3 MaxFlow pipes come in Race, 200-cell and 400-cell options, and Spool sells its 5 inch pipe as a 200-cell catted version. Our catless vs catted downpipe guide explains the trade-offs in detail.
Catless and high-flow downpipes and other emissions-related parts are intended for off-road and competition use and may not be legal for road use where you live. Check your local laws and inspection rules.
What to Do at the Same Time
- Tune: listings note that a check-engine light may occur and recommend a supporting tune. Plan it before the install.
- Charge pipe: the factory plastic charge pipe is a known weak point once boost goes up. See our B58 charge pipe guide.
- Heat and hardware: check the condition of the factory clamps, gaskets and oxygen sensors while everything is apart.
Parts and Tools
- IRL F30 340i B58 MaxFlow Downpipe — Gen 1 F30 340i
- IRL G-Series B58 Gen 2 MaxFlow Downpipe — Race, 200-cell or 400-cell
- IRL B58 Gen 3 MaxFlow Downpipe — Gen 3 B58TU2
- Spool B58 Gen 3 4 Inch Race Downpipe — consistent 4 inch design for Gen 3 (also listed for the Toyota B58 Gen 3)
- Palenon B58 Gen 1 / Gen 2 5in Race Downpipe — one pipe for Gen 1 and Gen 2 cars
- Rvng Gen 3 B58TU2 6" XL Flow Downpipe — largest inlet for the Gen 3 engine
- Spool B58 5 Inch 200-Cell Catted Downpipe — catted option for Gen 1 and Gen 2
- O2 Sensor Socket & Thread Chaser Set — for moving the oxygen sensors across
See all B58 parts and tools in BMW B-Series (B38 / B48 / B58), or compare every downpipe in Exhaust & Downpipes.
Shop: BMW B58 Downpipes and BMW B58 Performance Parts.
Install Overview
Exact steps vary by chassis and xDrive vs rear-wheel drive, so follow the instructions supplied with your pipe. In general:
- Let the exhaust cool completely and raise the car on jack stands or a lift.
- Remove underbody panels and any heat shields in the way.
- Unplug and remove the oxygen sensors.
- Release the clamp at the turbo outlet and the joint at the mid-pipe, then remove the factory downpipe and its brackets.
- Fit the new pipe loosely, align the flex section without twisting it, then tighten from the turbo back.
- Refit the sensors, panels and shields, then start the car and check for leaks.
Many listings recommend professional installation. If you do it yourself, never work under a car held only by a jack.
Frequently Asked Questions
Will a Gen 1 B58 downpipe fit a Gen 2 car?
Sometimes. Some brands build one pipe for both generations and list both in the fitment; others sell separate pipes. Follow the listing's fitment, and never fit a Gen 1 or Gen 2 pipe to a Gen 3 B58TU2.
Does a B58 downpipe fit the Toyota Supra?
Only where the listing says so. The Rvng 5 inch Gen 1 and Gen 2 pipe, for example, is listed as also fitting the GR Supra.
Do I need a tune for a B58 downpipe?
The listings recommend a supporting tune, and a check-engine light may occur without one.
Which size should I choose?
For a stock-turbo car with a tune, 4.5 to 5 inch is the common range. The larger sizes are aimed at higher-power builds. Sound also changes with size, with Spool describing its 5 inch pipe as deeper in tone.