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Anyone Cut Open A Backbox? Tdi 8p Chassis...

Discussion in 'A3/S3/Sportback (8P Chassis)' started by Tom93, Aug 18, 2014.

  1. Tom93
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    Tom93 New Member

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    [Aug 18, 2014]
    Yo, im thinking of cutting open the backbox on my A3 and attempting to remove everything from inside so its empty then welding it shut again, just wandering if anyone has done this before? It would cost me nothing to do but if someones already had a go and its a complete nightmare it might not be worth my time... Cheers me dears! :kissmyrings:
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  3. peaky83
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    peaky83 Member

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    [Aug 18, 2014]
    Hi Tom,

    What do you aim to gain from this? And from my experience of cars, what exactly do you think the back box is 'full' of? :uhm:

    They aren't really full of anything you could remove I don't think... You'd be better removing the middle silencer or baxkbox alltogether, but I go back to my original question of what are you trying to achieve?

    Cheers,

    Dan
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  4. Gazwould
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    Gazwould Active Member

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    [Aug 18, 2014]
    Surgery on silencers is best done with leaving a straight through pipe inside.
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  5. Dan-Jnr
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    Dan-Jnr Active Member

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    [Aug 18, 2014]
    Some back boxes have material inside them to dampen the exhaust noise, and some have baffles.
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  6. Tom93
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    Tom93 New Member

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    [Aug 18, 2014]
    Just trying to get some more noise from it really, i imagined it would be a maze of pipe work, cheese graters and wire wool, but i havent took many backboxs apart so im unsure! Im well aware putting a pipe in would be the best situation but then i might aswell just make a backbox bypass pipe... This was literally an idea that would cost me nothing and well im a tight arse. I got a quote from powerflow for a full turbo back system but its just so much money when i made a full 2.5" system for my 205 for about 50quid! But it was a bit **** and only really good for a peugeot, the Audi deserves something decent. Hence the full empty OEM idea... Its just an idea, i might be a little bit mad.
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  7. hollow
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    hollow Active Member

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    [Aug 18, 2014]
    just done this on a mk5 golf gt tdi which uses the same back box just converted it to the r32 look .there wass nothing inside the back box .no baffles at all just the 2 exhaust pipes that run nearly the full length of the box and the inlet that runs the opposite way.tbh never seen a box so full of soot . but there well constructed and are twin wall stainless .took a few hours to re construct the exhaust outlets ,weld up etc .no difference in noise at all
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  8. desertstorm
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    desertstorm Well-Known Member

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    [Aug 18, 2014]
    I cut open the rear box and middle box o my Passat 1.9 TDI and found the rear box to be full of baffles and several tuned pipes with holes in and was designed to be a muffler. The middle box was a lot less restrictive and was just a resonator.
    I found replacing the rear box with a straight through pipe slitghtly improved the pick up and performance but didn't get too much of an increase in volume. Even with a completely straight through system with no cat the exhaust is not that loud.
    These are pictures of the rear box in my Passat

    [​IMG]

    [​IMG]

    Karl
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  9. Tom93
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    Tom93 New Member

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    [Aug 18, 2014]
    Thats what i imagined it would look like ^^ My idea was to literally pull all of that out so its an empty box and put it back, surely its the change of direction to the exhaust gas that kills performance...

    But i wont be doing it if hollow has the same box as me, i was guessing it would be something like the one pictured above...
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  10. thesmileyone
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    thesmileyone Member

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    [Aug 18, 2014]
    I spent ages trying to find this out Tom, even offered £5 to anyone on here who could find me one...no luck.

    I spoke to a shop today about having it cut open, sorted and re-welded looking about £150. My car is a 1.8 TFSI though, at the moment it is pretty much silent so I wanted to subetly change it.

    I have done the res already and it just made my car gurgly and not really in a good, refined way, I have also done backbox delete with straight pipe both with and without the res in, without it sounds like an OTT racecar/saxo, with it sounded good but droned to the point of annoyance and headaches.

    I have decided to try fitting a mk5 gti backbox (they are the same as mine but with less baffles inside I believe).

    I also did a kind of silly experiment of driving hard and spraying cold water inside the backbox (well documented on BMW forums, people do it to brand new M3's!!!!) to try and break down the fiberglass insulation, which has not worked and leads me to believe there is no insulation, just baffles.
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  11. hollow
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    hollow Active Member

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    [Aug 19, 2014]
    the one I did was for family .my sister in law to be exact so didnt cost her a penny of cash or sweat . the tdi box on the a3 is wider than longer goes nearly the whole width of the boot pipe enters in the middle of the best way to describe pancake box and thexits to the left with twin pipes . by the time it was finished the box was empty and the twin exhaust pipes exit approx 8" apart it does seem to make a difference in power .could just be a placebo effect but it removes alot of oiping restrictions . anyone wanting it done pm me .
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  12. Tom93
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    Tom93 New Member

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    [Aug 20, 2014]
    Well i have bought some pipe to just make something instead of faffing about with the box, will just lop it off and put some pipe in. Will cut out the resonator box aswell if i have enough pipe. Also i will make a guide so everyone knows how i done it, where should i put a guide? Just a new topic in here labeled guide? Or is there a section i have missed? Sorry im new :meeting:
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  13. thesmileyone
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    thesmileyone Member

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    [Aug 22, 2014]
    Do you have pics of the inside?
    My backbox is the same as a tdi backbox, which is also the same as a mk5 golf gti backbox...atleast from the outside.
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  14. thesmileyone
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    thesmileyone Member

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    [Aug 22, 2014]
    Should have bought mine - I have a rear backbox replacement for sale :p
    [​IMG]
    http://www.audi-sport.net/xf/threads/custom-exhaust-parts.224006/#post-2230928
    #13

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