Advice on exhaust fab materials?

  1. Finalreminder

    Finalreminder Professional amateur

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    245
    Location:
    Denbighshire
    I'm wanting to build my own Exhaust manifold for my S3 Landy.
    Where would I get the tubing from and have it bent?
     
  2. malcolm

    malcolm Hej!

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    Bedford UK
    Millner Offroad are good for pre-bent tubing in stainless. They can do the mounting flange for some engines too.
     
  3. Finalreminder

    Finalreminder Professional amateur

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    Denbighshire
    Sweet! Nice one Mal:)
     
  4. malcolm

    malcolm Hej!

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    Another think that's occurred to me - my local motor factors have a load of tube bends and straight pipe in their aftermarket exhaust catalogue. Guessing mild steel and more suitable for pipes than manifolds.

    Might have a check today - MOT man had insisted I get around to building that new exhaust.
     
  5. piman Member

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    1,704
    Location:
    Oswestry Shropshire
    Hello Egg,

    as you are on the Wirral, Demon Tweeks in Wrexham is not too far. They stock all sorts of bends, pipes, even perforated pipe to make your own silencers. Personally, stainless is rather expensive when you start adding all the bends you need.

    Alec
     
  6. Finalreminder

    Finalreminder Professional amateur

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    245
    Location:
    Denbighshire
    Yeah Demons isn't far, I'll have to nip in after work next week and see what they've got.

    Mal:
    Can I use mild steel? I'd rather use that if possible being cheaper.
    Or maybe build a prototype from mild steel
     
  7. malcolm

    malcolm Hej!

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    Nothing wrong with mild steel for manifolds. Manifolds get quite hot so don't tend to rust badly from the inside. You'll get surface rust on the outside though that's a decorative issue. Should go to 2mm wall thickness for a manifold.

    Demon Tweeks tend to be pricy.
     
  8. Finalreminder

    Finalreminder Professional amateur

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    Location:
    Denbighshire
    Aye you're not wrong about Demons:eyepatch:

    I've had a think and I've decided to go with stainless. that site you offered up is excellent, plus I dont want to fab another one up in 5-10 years.

    Cheers Mal, you've been a great help[​IMG]
     
  9. ngt Saturated..

    Messages:
    126
    Greece
    There are two types of stainless.
    304 which is non-magnetic and the 409 which is magnetic it does not hold polishing as 304 but its cheaper and i believe far superior than mild steel (i think most of the catalytic converters are from this type of steel)
    Since the store has that great variety of items go for stainless !
     
    Last edited: Mar 8, 2008
  10. Hitch

    Hitch Moderator Staff Member

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    11,959
    Somerset
    I would think 321 would be a good stainless to use, higher temperature restance. Costly stuff though :laughing:
     
  11. TechnicAl

    TechnicAl Member

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    Location:
    Rotherham
    As ngt says 409 is often used for exhausts and Cats. It has an advantage in that it is resistant to Sulphur in the fumes and its cheaper.
    The Nickel bearing stainless steels are prone to corrosion from the Sulphurous gases. 409 probably extends the life by a couple of years so to most of us it probably doesnt matter.
    The problem with 409 is that its not as easy to weld. The manufacturers use 307 grade which isnt that common. 309L will do the job.
     
  12. Finalreminder

    Finalreminder Professional amateur

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    Location:
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    I'll opt for 309L then. I'll get some 409 to experiment on.
     
  13. Avocet New Member

    Messages:
    3
    Location:
    Cumbria UK
    Hi everyone, I'm new on here and have just come across this thread in a search, so I'm resurrecting it, as it's pretty close to the question I was going to ask. I have an old and (nearly) worthless Landrover Freelander, whose centre silencer is starting to fail. For some bizarre reason, Landrover decided to make the centre box part of the same welded assembly as the cat! To replace it with genuine would cost more than the car is worth, however, I've bought a universal silencer of about the right dimensions on eBay for under £50. It's advertised as being T304 stainless. As far as I can tell, the pipes going into and out of the original Landrover system are 409 stainless. They're magnetic and not uniformly rusty, but do have a fair number of rusty surface "scabs" on them. It certainly doesn't look like aluminised mild steel.

    I'm not looking to make the car last forever (another couple of years perhaps, as the shell is remarkably rust-free so far) but was just wondering if anyone had any recommendations for a MIG wire to use to weld the two together? I currently have 0.6mm mild steel wire in there, and if that'll get me a couple of years, I'd be happy, but I'd also not be averse to buying a small roll of something better if it would give a significantly better job. Gas is Hobbyweld 5 (which I think is 93% Argon, 5% Co2 and 2% O2).
     
  14. gt6s Member

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    696
    Location:
    Newtownards Co Down Northern Ireland
    If you only want it to last a couple of years mild steel wire will do. Your gas will be fine too
     
  15. Avocet New Member

    Messages:
    3
    Location:
    Cumbria UK
    Thanks gt6s. Just for interest, what SHOULD I use for best results trying to join 409 to 304?
     
  16. gaz_moose Member

    Messages:
    937
    Location:
    tamworth staffordshire
    id just mig it with what ever wire is in the mig. it will be fine for an exhaust, no point buying a whole roll of wire for one job.
    most silencers fail where the pipe enters the box due to flexing, welding a 'brace' a couple of inches long from the boxes outer flange down to the pipe will massively reduce this.

    tbh for an exhaust on an old banger I would just sleeve the joint and use U-clamps.
     
  17. Avocet New Member

    Messages:
    3
    Location:
    Cumbria UK
    Thanks gaz_moose. Yes, I intend to brace the ends of the silencer to the pipe. I know the Freelander is only a "toy" offroader, but Landrover made the centre box the lowest part of the car - and right in the middle of the wheelbase too, so it's the first thing to get bashed if you go over a crest with a rock sticking up through it! They have a small piece of sheet steel going from the bottom edge of the silencer up to the underside of the exhaust pipe at about 45 degrees. I certainly intend to try and preserve that. I can't clamp it because there's a bend in the pope too close to the inlet to the box, so I'll have to weld.
     
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