If I try to get a 3" downpipe made for 850R

Hi all,

For quite a while now I have been looking into upgrading the turbocharger of my 1996 850R, and doing a turbo back exhaust upgrade. Whilst turbos (and the ecu to take advantage of them), cat converters and cat back components look pretty easy to find, downpipes much under $1K seem rarer than hens teeth here in Australia.

After looking for these new and used for a long time, I'm thinking I might need to find a reputable shop that will fabricate a mandrel bent downpipe. I understand that I could take the car to one of these places and have them remove the existing downpipe, replicate it with 3" mandrel bent piping, and put it back together again, but since I'm considering going to the effort of a turbo upgrade (19T) i figure i might as well put in one of the larger outlet, angled flange turbos to get full returns for the effort.

The issue is that if i swap to this turbo, i can't exactly drive it to the shop with no existing downpipe to fit it, and I imagine it'd be pretty hard/impossible for them to determine dimensions for a downpipe to fit a turbo that isn't even on the car if i was to take it to them as is. I would think that they could manage to get the cat converter end made fine if i just bought in the downpipe, but as mentioned i reckon asking them to build a downpipe to fit a different turbo might be a big ask without it being fitted to the car.

Anyone had a similar dilemma, or know of any accurate plans getting around online that people have successfully had them fabricated from or anything?


  • Have car towed to exhaust shop for $80?
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    Yeah I agree, this is definitely a case of just get the car towed to the shop.
  • Yeah righto, either that or I'll drive it there, give them new turbo and tell them to install that while they are doing the exhaust work.

    I called a place in Newcastle today who said it'd be between about $1350-$1500 for turbo back system with downpipe made from mandrel bent sections. The guy didn't sound like a complete drongo so gave me some confidence, however i think he said that at least the dp would be mild steel. Given the popularity of SS systems, is this a deal breaker or a minor issue given we don't salt our roads etc.?
  • Vee_QueVee_Que (@Vee_Que) South Eastern suburbs Melbourne.
    edited March 2017
    Personally, I see no gain in a stainless system, it sounds tinier and will still rust, if you have mild steel coated in hpc coat or similar, and wrap it, they don't really give grief in Australia. It's more of A gimmick to charge more for thinner wall material. And stainless is harder to weld neatly, especially when thin.
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    edited March 2017
    @Julian I had a 2.5" turbo back system done at Performance Exhaust Centre in Northmead, $1200 fixed-price quote.

    Regarding stainless steel, I agree with @Vee_Que, we don't salt our roads or whatever so exhaust longevity is good.
  • GhettobirdJulian (@Ghettobird) Melbourne - SE Suburbs
    Drive it there with no downpipe... Itd be hilarious!

  • Lols
    Even 20v sounds like a tractor
  • Hey @jamesinc , did the exhaust you had made have a downpipe fabricated from several mandrel bent pieces of donut welded together, or was it one continuous mandrel bent sweep? The shop I talked to said they'd do it with multiple pieces welded, not sure if that's an issue or not, since even cheap brands like obx look to have a single bent pipe for dp.

    I'm thinking that since I'm not really sure about what ecu tune/upgrade is best for me (was thinking ARD but seems to be a large amount of negative feedback upon further research), i may just leave my standard turbo for now, but fit the larger angled flange compressor housing and have a turbo back exhaust built for that. Then I can just go and swap to a 19T later if i can decide on a reputable, tried and tested tune.

    I'm probably going to go for a 3" dp with 2.5" after that, which seem to be popular on here. Or is full 3" meaningfully beneficial? Out of interest, what muffler did you end up using? I want my car to be a bit louder but not "defect me please" loud, so would be good to hear how you've found yours.

  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    Several pieces welded together, which isn't a problem at all and looks fairly neat in the end.

    Having one continuous piece would make sense if you're mass producing it I'm sure, but otherwise you just make it from pre-bent pieces.
  • Vee_QueVee_Que (@Vee_Que) South Eastern suburbs Melbourne.
    I put 3" exhausts on any turbo car I work on. Muffler choice is important there, an offset straight through loses no flow, but loses a lot of noise, combined with a second straight through muffler that's well baffled, you won't get attention seeking loud.

    Going to a 2.5" you negate the work done at the downpipe, it slows the gas flow down as it just needs to escape on a turbo car. Honestly, going to a 2.5" is about laziness of the installer and the owner not wanting to spend another $200 for more flow.

    Cut and welded is normal for one off exhausts as you need a die to make a one peice unit.

    Will you be going bigger injectors also? That's important, as well as an all alloy intercooler, the stock ones are worn out at this point and susceptible to cracking etc.

  • edited March 2017
    Ok, I'll look into a full 3" system and see how much more they'd charge. Someone above mentioned getting a mild steel exhaust coated in hpc or wrapped for longevity- what is hpc and what is wrapping? Is this something a half reputable exhaust shop making a custom exhaust would do anyway, or is it important to ask for this?

    I'm not too concerned about injectors or IC at the moment, since I'm thinking that my first step will just be to put a 7cm angled flange turbine housing on my current turbo and get the turbo back exhaust done, with any change of turbocharger to come later once I've decided what tune to go with. So I'd imagine current fuelling and intake air cooling should still be adequate (correct me if I'm wrong though).

    I was about to buy a 7cm angle flange turbine housing, then saw that the seller also sells a plate to allow mating of a 3" pipe to the outlet. I take it i also need one of these for my 3" downpipe plans? These are $75, which seems pretty steep to me- reckon most exhaust shops would just machine up an adaptor for the exhaust, or would it be a good idea to supply them one?
  • SpacSpac (@Spac) Canberra-ish.
    HPC is a brand of ceramic coating. Good for appearance, and good for keeping heat in the pipe (and therefore out of the engine bay). Also very expensive last time I heard any dollar figures.

    Wrapping is a non-adhesive "bandage" that you wrap around the pipe and it acts as thermal insulation. Uglier than HPCoating, but significantly cheaper. Some horror stories about it holding water/oil/petrol and causing rust or fire issues, but these usually relate to rarely used cars (rust) or catastrophic failures (fire).

    Full 3" systems are prone to droning at constant throttle. This can be avoided with good muffler selection and some experimentation, but this can make the cost blow out.
    Dropping from 3" to 2.5" after the cat converter is a reliable way to avoid droning, without totally killing the power. Remember that the cat takes quite a lot of the heat out of the exhaust gases, so the cooler exhaust takes up less room - hence hurting the power output less than you'd probably think. But a full 3" system is definitely better for outright power (depending on what motor, how much boost, etc).

    I would buy the flange with the turbo. Most shops will change you at least that much, and will give you a perfectly functional but uglier hand-cut flange.
  • Righto, I've ordered a housing and the adaptor for 3" pipe now, so it's underway. Guess I'll go drop the car along with the housing at the 'zorst shop once they arrive! I'll ask the guy at the shop what he reckons between 2.5 and 3 inch cat back, see if he thinks drone will be bad with a 3 or if it can be cost effectively eliminated with mufflers
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    On Nina's 244 we're running a single muffler at the rear and a hot dog where the front is, 2.5" turbo-back, no drone at all. It's too quiet actually.
  • Vee_QueVee_Que (@Vee_Que) South Eastern suburbs Melbourne.
    edited March 2017
    My 740t wagon has little drone, with a bigger turbo and better flowing housing, and a full 3" exhaust, I went from a 2.5 on the car to a 3" and gained lower down boost, so it does make a difference if you actually want to go faster.....

    Ceramic coating is not cheap, but will reduce the chance of rusting. Most exhaust shops will say go for a 2.5 purely out of laziness, it takes more effort to do a 3" and order good mufflers to suit. Wrapping isn't normally done by the exhaust shop cheaply, i recommend doing it as you lose the factory heat shielding on the stock downpipe when you upgrade. Use titanium wrap, as it's less maintenance than fibreglass wrap too.
  • When I eventually get this gear into the car, will I need to modify anything to do with wastegate actuation? Just wondering if the wastegate arm will be in a slightly different position on the new turbine housing and will require me to change how the actuator is set, or whether I'll just disconnect the actuator arm and reconnect into the new turbine housing as is.
  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    The actuator arm probably just needs to match the cold side it's mounted to, but I could be wrong. The hot side should be the same relative dimensions regardless of flange type.
  • When I eventually get this gear into the car, will I need to modify anything to do with wastegate actuation? Just wondering if the wastegate arm will be in a slightly different position on the new turbine housing and will require me to change how the actuator is set, or whether I'll just disconnect the actuator arm and reconnect into the new turbine housing as is.

    No, Only 2 versions of the WG... one thats adjustable length and one fixed length
    Same WG works on Conical/flat/angeled housings
  • Ok cool beans, so even if mine is non adjustable the arm should just connect up to the new housing?
  • Ok cool beans, so even if mine is non adjustable the arm should just connect up to the new housing?

Sign In or Register to comment.