BMW 1 Series Exhaust System: Specs, Fitment & Common Faults
A genuinely important, technical clarification: there's a separate SCR component after the DPF that combines exhaust with AdBlue to convert NOx — simply fitting a cat without the DPF won't achieve much and will likely fail an MOT emissions test.
Illustration for editorial purposes
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OEM Part Number: confirm via VIN — Rear silencer (aftermarket) Bosal 247-037 / Walker 05924
| Rear silencer (back box) — aftermarket | Walker 05924 (1170 mm); Bosal 247-037, 247-413, 247-981; Ernst 251006; MTS 01.60519 (580 mm); Polmo 03.28, 03.07 (without cat); Vegaz BS-451 (999 mm), BS-83, BS-376; Hella 8LD 366 026-991 |
|---|---|
| Centre / intermediate silencer — aftermarket | Vegaz BS-134, BS-136, BS-140, BS-294IMA, BS-295 (centre); Polmo 03.51, 03.63; Ernst 275002, 275040 (repair, 750 mm); 4MAX 0219-01-00318P; No Bosal, Walker or MTS. |
| Front pipe / catalytic converter (DPF on diesels) — aftermarket | Bosal 090-201 (Euro 4/5); Vegaz BK-315 (Euro 6), BK-303, BK-843; BM Catalysts BM92647H (Euro 6, with FK92647); JMJ 1091548 (pair), 1091524, 1091729; Ernst 465144 (flex pipe only) |
| Genuine (OE) numbers quoted | None quoted in catalogue listings — order genuine parts against your VIN |
| Fitment notes | Petrol 116i-M135i and diesel 116d-120d; not engine-specific. |
BMW 1 Series Exhaust System: The Part That Announces Its Own Problems
On the BMW 1 Series, you'll typically hear this fault developing long before you'd ever see it — a new rattle, an odd drone, noise levels creeping up from one week to the next. That early audible warning is a genuine head start on catching the problem before it worsens.
BMW 1 Series Exhaust System: What It Does
The BMW 1 Series's exhaust does more than just carry gases away from the engine — it also handles noise reduction through the silencer and emissions treatment via a catalytic converter and particulate filter. That's why petrol and diesel versions can use entirely different systems.
BMW 1 Series Exhaust System: Watch: Replacing It
F21 3-door shares the F20 platform; back box delete.
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A Genuinely Important, Technical Clarification Worth Knowing — BMW 1 Series Exhaust System
If you're considering having the DPF removed on this diesel, this is genuinely important to know: there's a genuinely separate component fitted after the DPF, called an SCR system, which combines the exhaust gases with AdBlue in the presence of a catalyst specifically to convert harmful nitrogen oxides into nitrogen and water. Simply fitting a standard catalytic converter without the DPF won't achieve much on its own, and the car will very likely fail an MOT emissions test as a result — worth understanding this distinction before assuming a simpler exhaust modification will work as expected.
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.
BMW 1 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.