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I knew i'd need to replace the P38's exhaust ever since buying it. It failed its first MOT on major exhaust leaks from a hole in the rear box and a big leak from the flange between the downpipe and midbox. I'd stuck some epoxy putty on there to get it thru the test and started looking for replacement bits.

I wanted stainless and cheap. Not an easy combo. Kept my eye on ebay and found this:

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Not ideal being straight piped, but cheap at 50quid and despite the listing not mentioning it, looked like stainless steel. So took a punt.

It arrived and seemed fine, so i decided to sort it out with a silencer. I had a stainless mid box that i'd removed from my brothers 320d BMW when he upgraded the exhaust, and figured it would fit nicely.

Removed old the rear box, it literally fell to bits:

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Then dug the small silencer box out the garage and welded it into the rear of the new exhaust, had it on and off the car about 6 times getting the alignment right, but got there in the end:

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I also had a nice tailpipe from an Audi A6, so carefully aligned and welded that on:

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Having got to this stage i had a working back box and was quite pleased, but the mid box needed attention. The front flange was leaking, and there was a hole rusted thru it beside the hanger, which had got much worse with all the hacking about thus far.

I decided to get a bit silly, and so used a bit of the old backbox pipe, to create a streight thru mid box. I plated over the hole in beside the hanger with some scrap steel (not shown in this pic, you can still see the hole):

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Having examined the front flange, i realised it was leaking because the round part on the downpipe side had crumbled away. After scratching my head i found an Audi exhaust clamp in the garage. These are nice, as they're designed to sleeve over the pipe and clamp on. So i cut the remains of the busted front flange off and set about figuring out how i can use the clamp.

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The clamp was designed for 65mm pipe, but the downpipe was 55 and the silencer was 60. Luckily i had some pipe kicking around so sleeved the box and downpipe up to 2.5" to accept the clamp.

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I didnt get it fully finished, as i took the backbox back off to paint up the welds to protect them, and proceeded to drop the damn thing on the ground and get the wet paint covered in mud.

So maybe tonight i'll repaint it and get the backbox re-hung.

It is LOUD. I only took it for a quick spin around the block, and that was also before i fixed the leaks. As expected really, my plan is to get a stainless mid-box for it as well, so i'll have it apart again at some point to sort that out, and that will make it somewhat more sensible. In the mean time i figured i'd enjoy a bit of V8 roar!

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I like it when people are inventive! Can you record the sound to make us jealous?
BTW, there are more Audi-parts that fit a P38, a heatercore for example. Then you are entitled to feature a new badge on the tailgate:
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To be completed with "quattro" if you wish :)

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I'll try to make a recording. I suspect it'll sound much worse on video than it does in real life, they often do! Camera phone mics just arent upto capturing such sounds!

First i need to finish reinstalling the backbox. I repainted it yesterday afternoon and left it to dry, but the wife was out in the evening and by the time i got the wee man to sleep it was too late to go start trying to fit the exhaust.

Just trying to decide how large a middle box to buy. I dont want to go too big and over-silence it again, but at the same time i dont want a sore head on the motorway!

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One I've just done has cats and middle box only,, straight through after that, certainly lets people know it's a v8, I've worked on quite a few with that set up. I got stainless all the way ( including hi flow cats) from east coast for less than 200quid, the cats are still in my garage, will/ might get round to fitting at some point, I like the quietness, then the rumble as you floor it, then they know it's a v8 😁

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full stainless for £200 sounds bargainy, not found anything remotely close to that, was that new?!

Theres some on ebay for £250ish, but they're only mid/rear and only for dual silencer cars.

When i looked at the exhaust, the rear box was fairly small and is a straight thru design anyway. The middle box is huge and uses a reflection design where the gas bounces around and changes direction numerous times inside. As a result the general concensus seemed to be that the mid-box is doing most of the silencing, and is the one to change as it frees up the breathing as well. But then my rear fell apart anyway, so i figure i do both.

Exhaust place online has suggested a 6x15" box to replace the middle i think. Not sure if i weld it in myself, or pay someone to do it though. I've only got mild steel wire in the MIG (hence painting all the welds), and trying to sort the exhaust alignment on my own while laying under the car isnt easy!

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I was once helping a mate fit the exhaust to a kit car that used a Ford V6 Essex engine. He'd got a set of tubular manifolds but the engine was converted to dry sump so the manifold hung down much too low so had to be modded. After cutting lumps out of it, we tried to tack weld it in place and then remove it to weld it properly but couldn't get in there easily to tack weld. Then we had a brilliant idea, Superglue it together in situ then take it off and seam weld it on the bench. Not such a good idea, the Cyanide fumes from hot Superglue damn near gassed the pair of us.....

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haha! Yeh, the other one i've seen with welding is folk cleaning parts with chlorinated brake cleaner. If theres any residue, when heated it turns to phosgene gas. I'm not sure the stuff we get here in the UK has tetrachloroethylene in it, but certainly in the US it comes in both flavours.

http://www.brewracingframes.com/safety-alert-brake-cleaner--phosgene-gas.html

Managed to get the backbox refitted earlier and fired it up. No leaks first time which was pleasing.Took a short video after a test drive:

https://www.youtube.com/watch?v=-LsUKMUO7XM&feature=youtu.be

The noise is interesting, from inside when driving its quite deep and boomy, but only when on the gas accelerating, cruising along is quite civilised. From outside when revving it, it sounds epic, like some sort of muscle car. Clearly its too much for daily use and it'll get fixed properly with a new centre box at some point, but it certainly puts a smile on my face :)

If we can end up with as much of the muscle car sound as possible, but just trim out a bit of the deep booming inside the car, that would be ideal. I suspect that dampening the deep boom will also kill some of the v8 rasp though :(

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Lol, epic is word :) you should be on Roadkill with a noise like that!

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yeh its not quite muscle truck territory, but its pretty decent!

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Sounds a little bit raspy to me, you need larger bore pipe to get it to rumble. Bit late now though.......

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yeh too big and it ends up droning though. I quite like the rasp! Oddly it only does that when revving it in neutral. When driving its a much deeper noise. You can sort of hear it at the end, unfortunately the wife stopped the video right as i opened the throttle!

The rear pipe is 2.5", the midbox is 60mm, and the downpipe is much smaller with a really nasty Y collector on it. I will eventually replace the mid section with 2.5 to match the rear. The downpipe niggles at me at i really want to sort it properly with a decent collector thats not horribly restricted like the factory one, but its too much work for little gain i think.

It also still has cats, and i doubt we'll achieve maximum V8 noise with those still present, but i dont really want to take them out as its MOT/Emissions hassle i dont need.

My end goal is something civilised but with a distinct V8 note though. This is just an interim step for a bit of fun. Once i get a new middle box and figure out how i'm fitting it it should be a bit more sensible.

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My only reference is this stainless system I had for my Classic, it gave a deep low rumble like a wooden classic boat. When revving it didn't get much louder.
Indeed no cats but I doubt it will make much difference because they are up front while the sound is composed during it's travel through the pipe.
There are also sportcats that give minimal restriction.
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