FSI Exhaust Back Box / Silencer

[markhux33]

Morning all and happy Easter,

The back box pipe on my FSI has rusted through just behind the sleeve clamp that joins the mud box to the back box (where the hangar attached). It completely snapped the pipe in half so not repairable.

I think the easiest route is to replace the whole back box and sleeve clamp. As seems to already have been identified on here...the FSI back box doesn't seem to be available anywhere anymore.

So the options seem to be:

1. Buy the 1.4 back box and adapt the 50mm FSI centre pipe to the 45mm 1.4 pipe.

2. Buy a universal free flow back box from power flow or cherry bomb or some such.

Any thoughts from anyone. My main concerns are changing the torque or fuel economy characteristics of the FSI from changing the back pressure.

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[Deleted member 20348]

Hi
If you have the funds, get a custom stainless steel box made to resemble the original one in order to preserve its aerodynamic design qualities.

Edit, have been looking at the cherry bomb gallery photos they do varied work and would most likely be a good choice to manufacture your item.

If going the Power Flow franchised dealership route, read some reviews of the garage first off.

 

[PlasticMac]

I think, the back box is the NOx storage cat.
Mac.

 

[Deleted member 20348]

Hi,
Thanks @PlasticMac.
I always forget how different the BAD engine and parts are compared to the BBY/AUA.

I took the opportunity to look up the 7ZAP data and there are a lot of manufacturers of pattern parts.
@markhux33, quite possibly that you will have already seen this data. Could be of use to others though?

 

[PlasticMac]

There's also a German company that does FSI exhausts, with wizzy twin pipes if you want.
No UK distributor though, so you're into duty payment on import, but I think they ship net of German TAV.

https://www.fox-sportauspuff.de/en/

Mac.
Edit: There’s a UK company,

Fox Stainless Steel Performance Exhaust Systems And Rear Boxes

Fox are a German performance exhaust manufacturer with a huge range of stainless steel sports exhausts with a wide choice of tailpipe designs and duplex exhaust systems

www.dcperformance.co.uk

who list Fox stuff, but not A2. I've messaged them, to see if they can order the FSI parts.
Mac.

 

[markhux33]

Interesting, I'll check those German ones out.

You're correct that the 8Z0253609 is the part I need but if you look closely on the parts catalogue there is a different letter at the end for each engine code.

The FSI specific part number is not available anywhere as far as I can see. There are loads of pattern ones available but they're all for the 1.4.

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[vagdream]

I had one of the Longlife exhaust franchises (Chester) knock up a copy box in Stainless Steel, seems to do the job, but not cheap.

 

[PlasticMac]

There's also a German company that does FSI exhausts, with wizzy twin pipes if you want.
No UK distributor though, so you're into duty payment on import, but I think they ship net of German TAV.

https://www.fox-sportauspuff.de/en/

Mac.
Edit: There’s a UK company,

Fox Stainless Steel Performance Exhaust Systems And Rear Boxes

Fox are a German performance exhaust manufacturer with a huge range of stainless steel sports exhausts with a wide choice of tailpipe designs and duplex exhaust systems

www.dcperformance.co.uk

who list Fox stuff, but not A2. I've messaged them, to see if they can order the FSI parts.
Mac.

DC Performance have replied to say that they can supply any of the Fox range.
Mac

 

[markhux33]

Thanks, those fox exhausts look lovely. Way too expensive for me right now though. I can get a pattern version of the BBY exhaust for £72 so I think I'll try that first.

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[Deleted member 20348]

Hi @markhux33,
When you are fettling the exhaust to fit your car would you have time to take photos of your work and add them to this thread? I'd like to see the process that you took making the adaptations to fit the back box.

As always good luck.

 

[PlasticMac]

What about the NOx storage cat? The combined NOx Sensor, and post cat lambda are mounted at the end of it.
Mac.

 

[Deleted member 20348]

Do you have a photo or close up of the section you are describing please Mac?

 

[markhux33]

What about the NOx storage cat? The combined NOx Sensor, and post cat lambda are mounted at the end of it.
Mac.

Mac I think the section you are talking about is forward of what I need to replace. I'm just replacing the back box (8Z0 253 609). Number 1 in the diagram here: https://audi.7zap.com/en/rdw/audi+a2/a2/2004-248/2/253-253080/

Worth mentioning: The BAD part number ends in a P. There are only 3 pattern parts listed for that.
The newest revision of the BBY (1.4) exhaust ends in an N and is very common.

The TDi version ends in an S and may also fit the FSi I guess?

 

[Deleted member 20348]

That's good info @markhux33

Do you know the diameter of the diesel rear silencer/back box pipework?

I could measure it on my vehicle if it's helpful?

 

[markhux33]

Looks like it's 50mm as well. So that would be a better fit than the 45mm 1.4 box but the only one I can find is the BBY 1.4 box (8z0 253 609N)

 

[Deleted member 20348]

Hi,
There's this for the Tdi 90
Have not researched it to check fitment.

Does it look right?
90tdi part code
8Z0253609S
Found another image in this post.

New Tdi 90 rear silencer.

I collected my new rear silencer from Audi Wakefield today. Being unique to the Tdi 90 it only took two days and that was on back order. I was pleased to see that it includes the new bracket and rubber hanger which appear to be its weak point. . Ta Dave :)

www.a2oc.net

 

[Deleted member 20348]

Another one on Ebay looks to be in good condition. Seller may split apart from the front section and just sell the rear, be worth asking them?

 

[markhux33]

Right, I've ended up ordering the Klarius AU363C which is a pattern version of the 8Z0 253 609S for the 42L tank version of the 1.4 TDi AMF / BHC.

Not sure if this will arrive or not as it's off ebay and it seems very uncertain if stock actually exists but it said it does so I went for it and if not I will get a refund.

After reading the German forums on A2-freun.de it seems the extra can / flap on 1.6 FSi is for extra quietness rather than anything to do with performance so the TDI version should be fine and at least it's also 50mm so won't require the adapter unlike the 1.4 petrol BBY.

If it doesn't show up I think I'll just put a flexi pipe and a cherry bomb universal back box on it and call it done. I think the world's supply of actual A2 back boxes is rapidly drying up. I called Klarius this morning and they said they haven't made any of the A2 boxes for years now so there's only what is still out there in warehouses.

I've attached a few photos of the removal tonight for interest.

 

[markhux33]

Hi all,

Thought I'd just update this thread now I've fitted the replacement. I ended up buying a Klarius AU363C off ebay. It's a pattern replacement for the 8Z0253609S that comes with the 1.4 TDi AMF and BHC engines. I went for this as it has a 50mm pipe (same as FSi) and the 1.4 petrol has a 45mm pipe.

As expected it didn't have that coke can type appendage attached to the back box and the back box itself seems to be slightly physically smaller.

The mounting hangars were in the same place though. The only issue was the pipe was about 80mm longer than the old one and the end of the pipe where it joins the mid box was flanged out to 52mm to overlap the mid-box pipe. Not sure if that's because the TDi has a different layout or it's just one of those inconsistencies of a pattern part.

Either way I cut 80mm off the end of the pipe to make it a normal 50mm OD tube and connected it to the old mid-box pipe (also 50mm OD) with a standard 50mm sleeve clamp and some exhaust jointing compound.

Driven it about 50 miles so far and seems good. Power and MPG are normal and it sounds as it did when I bought it.

From combing the german forum it looks like the coke can thing was a valve to help reduce the noise for german regulations at certain RPM so I think it's fair to say that if you don't care about that the 1.4 TDi box is a good replacement.