Noise goes during DPF regeneration

[AnneTeak]

Hi, I wondered if someone could explain anything that changes within the car's mechanicals when a DPF is regenerating... Is it largely just a temperature increase in the exhaust? It's a Volvo D5 engine.

The reason for asking is I have a strange vibration noise which only occurs at a certain RPM (2k, in all gears and neutral). Here's a video of the noise. However when the DPF is regenerating (the car tells you this), the noise completely disappears. The noise is louder when the car is cold, although never completely goes, expect during a regen.

Any ideas?

[E-bmw]

As you say, the main one is heat.

Heat....Noise....Expansion.....Heat shield would be my first port of call.

[anonymous-user]

No ideas I'm afraid, but how does the car tell you the DPF is regenerating? I've had a few Volvo D5s of various models and vintages and without VIDA never known how to tell!

[AnneTeak]

Does anything happen different in the engine and it’s pipes? The exhaust gas always goes through the DPF/cat box (on the downpipe), therefore is the only difference when re-generating that the exhaust gasses are trapped in the box on its way through?

@dme123 you can tell from going into the car menu and clicking DriveE > Start/Stop and It’ll say “engine management system” (when you click it says parciulate filter regeneration). You can also hear a different noise from the exhaust pipes (hissing).

[GreenV8S]

AnneTeak said:

Does anything happen different in the engine and it’s pipes?

As I understand it, active regen consists of injecting extra fuel and changing the injection timing to raise the exhaust temperature; it doesn't involve any changes to the exhaust system or DPF operation.