Hi. I've recently bought a 65 plate 2.0tdi instead of a 2010 vrs tdi.

Looking underneath there's a 'thing' in the exhaust towards the front under a heat shield that wasn't there on the old car. It looks like some sort of valve like is on my BMW RT bike.

What is it?

Thanks

Edited 2 April2 Apr by PhilChapman1964

On 03/04/2026 at 08:27, PhilChapman1964 said:

What is it?

CAT?

Flexible coupling?

Flange?

muffler?

DPF?

Turbo???

I dunno man, maybe post a photo man, then we can have a look and a better guess man

Edited 5 April5 Apr by BlueWagon

Funnily enough, I asked the same question when my mechanic had my car up in the air last week. I thought it was a "valve tronic" type jobbie, so when you put your foot down it opens more, but apparently not.

If its the same thing you're talking about, its a valve which opens/closes when doing a DPF regen. So it restricts the flow and increases pressure in the DPF, to make it run hotter, for a more effective regen.

At least, that's what the mechanic told me, and how I interpreted it anyway.

Others here may be able to elaborate, or tell me i'm wrong. 🤷‍♂️

That's interesting and thanks for replying.

I've not had the chance to get under again to look. I know that the other car didn't have one.

So it must affect performance if it's restricting flow.

Cheers

Not to worry, floor the accelerator and you might be near twice the national speed limit in the UK before you need to lift off.

Its probably the back pressure control valve, I just found mine has one (2015 vRS TDi) and it wasn't plugged in, since plugged it in and the cars running much better now... which is probably not a surprise.

I imagine that the valve will open and close at different rates, depending on how you are driving the car.
Open when giving it some beans, as the DPF will be getting plenty of flow anyway.
And closed when sat in traffic etc.

From what I understand it is all linked to the fuelling and the EGR system, so DPF as well as noted above. Not entirely sure how it all ties in but helping with regen of the DPF makes sense.

3 hours ago, PhilChapman1964 said:

That's interesting and thanks for replying.

I've not had the chance to get under again to look. I know that the other car didn't have one.

So it must affect performance if it's restricting flow.

Cheers

It will restrict flow, along with the carbon buildup, DPF, catalytic converter, EGR system, backbox, resonator(s), the OE downpipe diameter, exhaust tubing, bends, joins and seals, along with the (if we're being specific) the turbo turbine housing and intake elbow.

It's a TDI. If you're mentioning restrictions and haven't gutted the DPF and done an EGR/swirl flap delete, you need to do some more research.

Without a photo, there isn't much we can work with - a 'thing' by the heat shield isn't very specific.