BMW 3 Series Exhaust System: Specs, Fitment & Common Faults
A genuinely useful finding: these engines can automatically sense when a regen is needed and raise the exhaust temperature themselves — plus a technical clarification about the separate SCR system, and a genuine fix for a downpipe rattle caused by loose bolts.
Illustration for editorial purposes
Opens live listings in a new tab.
The Part That Announces Its Own Problems
Where a lot of BMW 3 Series parts fail silently until you spot something visually wrong, this one tends to make noise first — a rattle, a drone, an audible change that wasn't there recently. That's a useful early-warning system if you're paying attention.
OEM Part Number: confirm via VIN — Rear silencer (aftermarket) Bosal 247-981 / Walker 05924
| Rear silencer (back box) — aftermarket | Walker 05924 (1170 mm); Bosal 247-981, 247-413; MTS 01.63390 (1100 mm); Ernst 275088, 251006; Polmo 03.28, 03.07; Vegaz BS-49, BS-83, BS-451; Hella 8LD 366 026-991 |
|---|---|
| Centre / intermediate silencer — aftermarket | Vegaz BS-294IMA, BS-295, BS-134, BS-136, BS-140; Polmo 03.51, 03.63; Ernst 275002, 275040; 4MAX 0219-01-00318P; No Bosal, Walker or MTS. |
| Front pipe / catalytic converter (DPF on diesels) — aftermarket | Bosal 090-261 (Euro 6), 090-201 (Euro 4/5); Walker 28182 (420 mm, with manifold), 28197 (650 mm); Ernst 750141 (manifold cat, Euro 3, cyl 1-3, probably not G20); Vegaz BK-304 (Euro 6 manifold cat); JMJ 1080006 and 1080164 (engine M47/M47N, an old diesel code, probably not G20); BM Catalysts BM91184H |
| Genuine (OE) numbers quoted | None quoted in catalogue listings — order genuine parts against your VIN |
| Fitment notes | Petrol, diesel, PHEV and mild hybrid; not engine-specific. |
M340i and M performance variants use a genuinely different exhaust system, including an electronically controlled valve that alters the exhaust note depending on drive mode — this is a distinct part from the standard 320i/330i exhaust and not a simple like-for-like swap. Catalytic converter theft is also a real risk on this car, as with most modern turbocharged petrol vehicles, given the precious metals used.
BMW 3 Series Exhaust System: What It Does
Away from the engine, through the silencer, and often through a catalytic converter and particulate filter before reaching the tailpipe — that's the BMW 3 Series's exhaust job in three steps. Petrol and diesel versions frequently need different systems entirely, since their emissions treatment isn't the same.
BMW 3 Series Exhaust System: Watch: Replacing It
F30 rear silencer work on a diesel.
Opens live listings in a new tab.
A Genuinely Useful Finding Worth Knowing About Regeneration — BMW 3 Series Exhaust System
If you're worried about the DPF on this diesel, this is genuinely useful to know: these engines can genuinely sense when the DPF needs to regenerate and will automatically raise the exhaust temperature to clear it during normal driving, meaning there's no need to manually select sport mode or a manual gear specifically to try to trigger this process yourself. It's also genuinely worth knowing a useful preventative tip if your regular driving is mostly short journeys: giving the car a proper, sustained run at higher revs for around 20 to 30 minutes every six to eight weeks has been documented as a genuinely useful way to ensure the DPF gets a proper opportunity to regenerate fully.
It's also genuinely worth knowing that a rattle or leak from the exhaust downpipe area has, in documented cases, simply been down to loose connecting bolts, worth checking and tightening these first before assuming a full pipe replacement is needed.
BMW 3 Series Exhaust System: Warning Signs, DIY Difficulty & Aftermarket Advice
These are the same regardless of make or model — see our full Exhaust System Guide for warning signs and fault codes to watch for, confirming fitment against your VIN, and which aftermarket brands are worth trusting.
More BMW Exhaust System
The same part, covered across other BMW models.