On the S63 V8 in the F90 M5, F91/F92/F93 M8 and F95/F96 X5M/X6M, the downpipes come in two sections. The primary downpipes bolt to the turbos inside the engine's "hot V", and the secondary downpipes continue down toward the rest of the exhaust. You can replace the primaries, the secondaries or both. Replacing both gives a fully freed-up path, and full race downpipe sets do the same job in one purchase. As with any downpipe, plan a supporting tune.
This guide explains the layout, what each section changes, which parts fit which car, and what else to plan.
The Hot-V Layout and Why There Are Primaries and Secondaries
On most V8s the exhaust manifolds sit on the outside of the cylinder heads. BMW's S63 reverses that: the exhaust ports face into the valley between the two banks, and the twin turbos sit there too. This "hot V" keeps the path from the exhaust ports to the turbos short, which helps response.
The trade-off is packaging. Exhaust gas leaving the turbos has to travel out of the valley and down past the engine and transmission before it reaches the underbody. That route is too awkward for one pipe, so the downpipe is split into a primary section (attached to the turbos, up in the V) and a secondary section (lower down, joining the mid-pipe). From the factory, the catalytic converters are housed in this downpipe path, which is why it is the main restriction behind the turbos.
What Each Stage Changes
| Option | What you replace | What it does |
|---|---|---|
| Primaries only | The sections bolted to the turbos | IRL calls the primaries the first step toward a freer-flowing S63 exhaust, improving sound and flow |
| Secondaries only | The lower sections | Reduces restriction further down the path; easier to reach than the primaries |
| Primaries and secondaries | Both sections | IRL describes pairing them as a fully freed-up S63 exhaust path |
| Full race downpipe set | The complete downpipe path | One purchase covering the whole section, such as the IRL MaxFlow Race or Spool race downpipes |
The Rvng XL Flow downpipes for the F90 M5 and F9X M8 can be ordered as primaries, secondaries or both, uncoated or with a high-temperature ceramic coating, so you can start with one section and add the other later.
F10 vs F90 vs X5M/X6M Fitment
The S63 has been through several versions, and the downpipes are not shared across every car that uses it.
| Car | Options in stock |
|---|---|
| F10 M5, F06/F12/F13 M6 | Palenon S63 Catless Race Downpipes |
| F90 M5 and F91/F92/F93 M8 | IRL primaries, IRL secondaries, IRL MaxFlow Race set, Rvng 3.5" XL Flow, Spool M5 and M8 race downpipes, STRATEC catted with heat shield |
| F95 X5M and F96 X6M | IRL primaries and secondaries (LCI), IRL MaxFlow Race (also lists S68), Spool race downpipes |
Pay attention to model-year notes. The IRL X5M/X6M primaries and secondaries are listed for the LCI cars, and the Spool X5M/X6M pipes give production date ranges. The G-chassis M550i, 750i and M850i use the related N63 engine and have their own downpipes, listed separately.
Catted vs Race
Most S63 options are race (catless) pipes. If you want to keep converters, the STRATEC F90 M5 catted downpipes use high-flow converters with an integrated heat shield. Our catless vs catted guide covers the trade-offs in sound, smell and emissions.
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.
Supporting Mods
- Tune: the Spool and Rvng S63 listings recommend a supporting tune, and the brands' power figures assume one.
- Low-pressure fuel: on higher-power builds, especially with ethanol, the in-tank pump becomes a limit. Spool offers Stage 3 LPFP kits for the F90 M5 and M8. See our HPFP vs LPFP guide.
- Intake: STRATEC sells a downpipe and intake kit for the F90 M5 and M8 that upgrades both sides of the turbos.
Parts and Tools
- IRL F90 M5 / M8 S63 Primary Downpipes
- IRL F90 M5 / M8 S63 MaxFlow Race Secondary Downpipes
- IRL F90 M5 / M8 S63 MaxFlow Race Downpipes
- IRL F95 X5M / F96 X6M S63 Primary Downpipes
- IRL F95 X5M / F96 X6M S63 Secondary Downpipes
- Rvng F90 M5 / F9X M8 3.5" XL Flow Race Downpipes — primary, secondary or both
- STRATEC F90 M5 Catted Downpipes with Heat Shield
- Spool Stage 3 Low Pressure Fuel Pump, S63 F90 M5
- O2 Sensor Socket & Thread Chaser Set
See all parts for these cars in BMW M5 and BMW M8, or compare every downpipe in Exhaust & Downpipes. If you are also servicing the engine, our N63/S63 timing chain and VANOS guide covers the timing side.
Shop: BMW S63 / N63 Downpipes.
Install Notes
Primaries sit in the hot V and are the harder job; secondaries are reached from below. Work only on a fully cold engine, as the turbos and pipes hold heat for a long time. Support the car on a lift or jack stands. Expect seized fasteners and oxygen sensors on older cars. Several listings recommend professional installation, and for primaries on these cars that is good advice.
Frequently Asked Questions
Should I do primaries or secondaries first?
IRL describes the primaries as the first step and pairing them with secondaries as the fully freed-up setup. If you plan to do both eventually, buying a full set or both sections at once saves doing the job twice.
Do F90 M5 downpipes fit the X5M?
No. The F95 X5M and F96 X6M have their own downpipes. Check the listing and model-year notes.
Do I need a tune for S63 downpipes?
A supporting tune is recommended in the listings, and the brands' power figures are quoted with a tune.
Are there catted S63 downpipes?
Yes. The STRATEC F90 M5 downpipes keep high-flow catalytic converters and include a heat shield.