Audi A4 Exhaust System: Specs, Fitment & Common Faults
On the A4, power loss and heavy smoke that looks like DPF failure can genuinely be a faulty exhaust back pressure sensor giving incorrect readings — plus a legal clarification that DPF deletes aren't actually legal in the UK.
Illustration for editorial purposes
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OEM Part Number: confirm via VIN — Rear silencer (aftermarket) Bosal 105-031 / Walker 13379
| Rear silencer (back box) — aftermarket | B8: Bosal 105-031, 105-127, 105-017, 105-137 (all need accessories); Vegaz AS-44 (940 mm, 5.24 kg), AS-86IMA (1070 mm), VS-37 (1040 mm), AS-190 (1070 mm), AS-313AT (1060 mm); Polmo 01.124 (with cat) / 01.14 (without) / 01.05 (manual); Izawit 15.003; Imasaf 13.51.07 (940 mm); Hella 8LD 366 026-701 (two-piece set). / B9: same Bosal 105-xxx set; Walker 13379 (1050 mm, code 53, OE 893253078C); Vegaz AS-44, AS-190, AS-313AT; Polmo 01.124/01.14; Izawit 15.003; Hella 8LD 366 026-701. |
|---|---|
| Centre / intermediate silencer — aftermarket | B8: Bosal 105-109, 220-015, 105-159; Walker 21575 (790 mm, code 52), 22719 (760 mm, code 62), 21903 (850 mm, code 52); Ernst 153003 (810 mm), 202046 (830 mm), 233026 (1080 mm), 114172 (900 mm); Asmet 21.009; MTS 01.59790 (880 mm), 01.59810 (900 mm), 01.53750 (1140 mm); Vegaz VS-293AT; Polmo 01.106/01.104/01.62/01.251 (with cat), 01.08 (front, without cat) |
| Front pipe / catalytic converter (DPF on diesels) — aftermarket | or DPF: Walker 28853 (610 mm, code 91, with fitting parts); Ernst 760737 (650 mm, Euro 4/5, set with mounting kit); Vegaz AK-890 (620 mm, Euro 5, OBD), AK-839 (650 mm, to Euro 5), AK-348 (Euro 6); JMJ 1091592 (620 mm), 1091566 (570 mm; engine codes CABA, CABB, CDHA, CDHB, CJEB, CAED, CAEA, CDNB, CFKA, CAEB, CDNC, CNCD, CPMA, CPMB); BM Catalysts BM92801H (Euro 5, only with FK92801), BM92109H, BM92110H, BM92108H (Euro 5). Bosal not listed for cat. |
| Genuine (OE) numbers quoted | None quoted in catalogue listings — order genuine parts against your VIN |
| Fitment notes | B8 engine range 1.8 TFSI to 3.0 TDI quattro with no per-part mapping; JMJ 1091566 engine codes (CAB*, CDH*, CAE* etc.) are the 2.0 TFSI/TDI B8 engines. |
Audi A4 Exhaust System: The Part That Announces Its Own Problems
On the Audi A4, sound is usually the first clue here, ahead of any visual sign — a rattle, a drone, noise that's crept in gradually or arrived overnight. It's one of the more forgiving faults in that sense, since your ears will likely flag it before it becomes a bigger problem.
Audi A4 Exhaust System: What It Does
The Audi A4's exhaust system handles three things at once: clearing burnt gases from the engine, cutting noise via the silencer, and treating emissions through a catalytic converter and particulate filter. Because petrol and diesel emissions requirements differ, it often uses genuinely different exhaust systems depending on engine type.
Audi A4 Exhaust System: Watch: Replacing It
Title only; B8 vs B9 not verified. B8 alt: https://www.youtube.com/watch?v=z3yquEC8JBU (muffler/resonator delete). B9 alt: https://www.youtube.com/watch?v=fs2IZ2SqVfo (iE catback vs stock).
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A Genuinely Money-Saving, Real Finding Worth Knowing Before Assuming DPF Failure — Audi A4 Exhaust System
If you're facing power loss and heavy smoke alongside a warning light, this is genuinely worth knowing before assuming the DPF itself has failed: one documented case saw these exact symptoms traced to a faulty exhaust back pressure sensor, which was giving incorrect readings and causing incomplete DPF regeneration cycles. Replacing this specific sensor and cleaning the exhaust system resolved the fault entirely.
It's also genuinely worth knowing an important legal clarification: removing emissions control equipment fitted to achieve type approval is already a legal requirement not to do in the UK, and while a "DPF delete" might currently pass an MOT test, this doesn't make the practice itself legal — worth knowing this carries genuine legal risk regardless of current MOT outcomes.
Audi A4 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 Audi Exhaust System
The same part, covered across other Audi models.