Oem downpipe diameter

[Doug_RS6]

Anyone happen to know what the oem down pipe diameter is? One of the flexis on mine is looking a bit worse for wear and planning to replace just the flexi on both downpipes as there is nothing wrong with the exhaust otherwise.

I have two 70mm diameter flexis lying around from something previous. I think they should fit as I seem to recall the RS6 having a 70mm exhaust.

[IanH755]

I think the entire stock/OEM exhaust is 2.5in (63.5mm) based on the Milltek Cat-Back being 2.75in (70mm) and being 0.25in wider than the downpipe when fitted.

However it';s been a long time since I touched an exhaust so my memory may not be perfect

[Doug_RS6]

Thanks. I don't suppose anyone has access to measure the downpipe just before the flexi to save me going out in the pouring rain?

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[Jim Haseltine]

As far as I can tell, with my calipers directly beside the flexy weld it's 67mm OD.

[Doug_RS6]

Yep. Pipe is 64.5mm checked it and realised i needed to order a different flexi.

[Jim Haseltine]

Judging by the carbon staining on the RH flexy I saw when I was using the calipers I suspect it's a job I need to do fairly soon so I'd appreciate info about what you use.

[Doug_RS6]

Will do. My intention was to cut off before the downpipe gets to the flexi and use a clamp joint there and then weld it to my secondary decat pipe which goes to the center section of the miltek exhaust.

[Jim Haseltine]

Cut open my wrecked flexy and the OD of the downpipe is pretty much spot on 64.5mm - give & take as it's not perfectly round.

[Doug_RS6]

I haven't revisited it yet. Mostly as I'm debating if there is enough straight pipe on the downpipe to clamp a sleeve joint on. Ideally I'd use v-bands but welding in situ would be difficult if not impossible.

[Jim Haseltine]

Correction - cleaned up the edges of the downpipe (there's a lot less inside the ends of the flexy than I thought there would be) and remeasured both of them, they're a touch under 64mm. I've found some turbo rated (triple layer, just like OE) flexy joints in T304 stainless which I'll offer up for fit later in the week.

[Doug_RS6]

Let me know how you get on please and if possible could you link them?

[Jim Haseltine]

https://www.profusionexhausts.com/63mm- ... tube-pipe/
I ordered them at around 3pm yesterday afternoon, they arrived just before 9am this morning. I've got to tidy up the old welds and the ends of the down pipe a bit more and take some burrs off the ends of the flexy so the parts will slide together without having to use a lot of force.

[Doug_RS6]

Are you welding them on at both ends?

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[Jim Haseltine]

Both ends. I cobbled a jig together with using some scraps of wood before I cut the old flexy and put some alignment marks on the pipe but even so getting both ends of the downpipe to sit in the correct plane will be awkward but at least the flexy means that they don't have to be 100% accurate.

[Doug_RS6]

Ah right. See i was going to make a sleeve joint at the down pipe end and then weld the other end to make one section from there to the centre section.