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Turbo Downpipe Options for my AAN powered 80 Avant

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  • Turbo Downpipe Options for my AAN powered 80 Avant

    I'm in the process of converting my 80 Avant to a S2 spec or similar and I am looking for downpipe that will fit the build.

    Currently I have the original AAN turbo downpipe which simply does not fit the B4 chassis shape.
    My options would be:
    - cut the factory turbo flange off and have something welded onto that (keen to keep this untouched to sell)
    - find a factory s2 downpipe (good luck for a reasonable price)
    - buy something aftermarket or have something made (leaning towards this)


    On the subject of something aftermarket has anybody had experience with this APmotorsport piece or can recommenced an alternative?

    http://shop.apmotorsport.pl/en/exhaust-systems/32-exhaust-downpipe-evo1-76mm-s2-rs2-s4-s6.html
    exhaust-downpipe-evo1-76mm-s2-rs2-s4-s6.jpg

    exhaust-downpipe-evo1-76mm-s2-rs2-s4-s6.jpg
    Last edited by 89 Coupe; 28 February 2023, 22:11.

  • #2
    That AP Racing one looks really nicely made and isn't that expensive, though neither is by any means cheap.

    A half decent exhaust fabricator should be able to make you up something for around half that price. The flanges can be purchased ready cut or the fabricator may have some in stock that'll do the job. The turbine exit is pretty generic it's a the waste gate one that's harder to find off the shelf.

    If you can weld then I'd make it yourself, use SS wire in a MIG and with spotless prep you'll get a tidy result, the various bends required and straight sections can be purchased very reasonably. I made up a Downpipe back system for my 3B using mild steel for about £100, though it would have only cost another 50 odd quid for SS pipe and bends, I went with MS as I wasn't sure how happy I'd be with end result. As it happens it turned out fine first try but the MS only had about a five year lifespan on salty UK roads.

    Have you got the rest of the system yet? As if you have then a second hand S2 one would probably be your best bet but if your starting from scratch you may as well simplify the design and opt for a single Cat, less weight and much easier to fabricate.

    I'd also avoid cutting up a perfectly good AAN downpipe just for a flange.
    1989 B3 2.0 3A 80 quattro... Budget 1.8T Project.
    1992 C4 100 2.8 Avant quattro... Mobile Sitting Room.
    1995 RS2... MTM K26/7 380 BHP Conversion.
    1990 Corrado G60... Breaking For Parts.

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    • #3
      Just an afterthought... You could fabricate your own wastegate flange out of some "1/4 plate using the the AAN one as a template, it would be little arduous but would only take a couple of hours with basic power tools and a couple of files. You can use MS for the flanges as they get so hot they'll only ever see light surface rust, it's best if you can bolt the main flange to a turbine housing to prevent warping when completing the weld.

      Also there must be a felixiable section between the wastegate outlet and the rest of the system as the sections will expand and contract at significantly different rates.

      I'm sure you could buy pre cut wastegate flanges from German eBay for about 20 euros for a pair, that's what I did when doing away with the screamer pipe.
      1989 B3 2.0 3A 80 quattro... Budget 1.8T Project.
      1992 C4 100 2.8 Avant quattro... Mobile Sitting Room.
      1995 RS2... MTM K26/7 380 BHP Conversion.
      1990 Corrado G60... Breaking For Parts.

      Comment


      • #4
        Thanks for such a detailed response Kit, it's given me a lot to think about.

        I know you are right about the fabrication option, it's probably going be the cheapest and best solution to the problem and I'll get exactly what I want that way.

        The plan is to mate the turbo and wastegate into a downpipe with a flexi like you said. Catless then join into a factory B5 S4 cat-back system. It is surprisingly similar to the B4, as we know it is derived from that anyway. I have already test fitted it and it wont take much to mount permanently.

        I do like the idea of having the wastegate separate as it's a fantastic noise but I think I'll keep it simple for starters.

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        • #5
          Unless you really like an unsettling noise every time you use some boost do not opt for a screamer pipe that vent's to straight to the atmosphere!!! They make one hell of a racket and I'd only ever consider using one on some sort of drag racing car. I thougt it would be a bit of fun, however I decided on my first test run that it had to go.

          I like the idea of using the B5 S4 exhaust, with no cat it should sound really nice without being too load... As you say they're almost identical underneath and yes, fit a flexi joint between this and the down-pipe.

          Jetex sell all the bends, pipes and flexi's required, they also sell generic three and four bolt flanges that could make mating your down-pipe to the rest of the system very straight forward.
          1989 B3 2.0 3A 80 quattro... Budget 1.8T Project.
          1992 C4 100 2.8 Avant quattro... Mobile Sitting Room.
          1995 RS2... MTM K26/7 380 BHP Conversion.
          1990 Corrado G60... Breaking For Parts.

          Comment

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