DRY EHXAUST vs WET EXHAUST-MATERIAL CHOICE

Discussion in 'DIY Marinizing' started by MihaS, Sep 20, 2013.

  1. MihaS
    Joined: Jan 2011
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    Location: Adriatic

    MihaS Junior Member

    Hello

    I have some problems about using material of building exhaust for my new project of marinising diesel engine.

    Engine is inline 6cyl turbo engine,with 160-190ps.
    Head is made from cast iron.

    1. which turbo diesel engines have wet/dry exhaust,hot do they resolve heat problems in dry exhaust.

    2. which material is best for make it.

    for wet exhaust:
    Im not so happy to use SS, AL is hard to weld nice.

    I speak with some guy which make before exhaust but he make it from steel pipes used for heating(MANESMAN PIPES) and steel shet used for making boiler(i use google translate)
    And can be welded good and its cheap.

    for dry exhaust :
    i dont know much



    Thanks for help


    my engine runing you tube:

    http://www.youtube.com/watch?v=U_XXONehPXs
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Wet and dry exhaust are handled very differently.

    Wet, once out of the manifold can be handled with standard exhaust hose, which permits fairly easy routing around things to it's through hull fitting. The manifold is typically cast iron (understandably), but if you want to make one, stainless steel would be the first choice, with mild steel a distant but easier welded second. The manifold material needs to be relatively thick as it's going to rust.

    A dry stack is easier, except you have very hot piping everywhere. It's treated just like any exhaust system, commonly with mild steel, but the pipes need lots of insulation if below decks and the exit will need special attention, again because of the heat. Dry setups are typically used when you can get the exhaust pipe out of the engine compartment and below deck areas quickly and up a stack. I've done some dry systems with triple wraps of header tape, backed by a reflective shield, but even with this arrangement, below deck heat will still be an issue.
     
  3. tom kane
    Joined: Nov 2003
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Build exhaust with 316 titanium stabilized Stainless Steel and water jacket the hot parts.Dry insulate the exhaust as well in case your water supply stops.
     
  4. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    With a wet exhaust, your biggest propblem is corrosion as you will be injecting salt water right before the manifold (unless you have an unlimited supply of fresh water).

    You also need a vacuum valve to prevent water in the "wet box" from being sucked up by the engine when it cools. You need also a high temperature hose to connect from the manifold to the wet box. There is some math involved to calculate the volume of water that will remain in the manifold and the wet box. This is the amount of water that will be "potentially" ingested by the engine when it cools unless a vacuum valve is inserted, Placement of the wet box comes into play.

    See Vetus for several types of wet box. Volvo Penta has some informative articles on the wet type volume calculations.

    As for the materials, I have used a high temperature fiberglass wet box and a heat sensor/alarm to monitor failure of the water pump/exhaust temp.

    For the dry type, your problem would be volume due to the bulk of insulation. Fiberglass/ceramic wool can be used to insulate, aluminum clad fireproop insulating canvass to cover, and perforated stainless steel to protect the insulation. On areas where it exits a bulkhead or deck, a fire resistant membrane is used to separate the hot exhaust tube from the structure. On areas where insulating material is not used (outside of the hull) you need a large gap between the tube and the protective cover (perforated steel). Air dissipate the heat,
     
  5. MihaS
    Joined: Jan 2011
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    Location: Adriatic

    MihaS Junior Member

    I have in mind doing something like this,but maybe not with tank on exhaust.

    http://www.youtube.com/watch?v=7SLLuxniVXk

    For SS ,I will probably dont use it. Because friend of mine make/produce 120 sets of mercruiser/volvo velded SS exhaust but people was vry disapointed. Some cracks inside, some gets water in engine, in one engine bolts was puled out of head. One customer said that engine got fire because those exhaust. I realy dont know and I dont want to test on me.
    SS is very tough and big shrinkage and elongation, I think.

    Engine will be cooled with fresh water,so also in exhaust manifold will be fresh water. Salt water will go thru heat exchanger and then to turbo elbow on the end.

    I also heard that must be exhaust manifold from material which is made engine head. Because when engine cools down or getting heat, gets temperature with same speed/time or geting of temperature. (MAYBE) .

    In VW marine engines they use ALU exhaust, and their engine head is ALU.

    VM have cast iron(gus) heads and they have made exhaust manifold from cast iron.

    I will probably get welded with seamless tubes and kness.

    My first choice was casting alu exhaust but there is some problem how to get sand out of product. So here is some drawaing I have made for casting.

    Also I remember that Yanmar 6lpty, have dry exhaust manifold i think. So exhaust is placed between engine block and header tank.

    Like you know this engine is base from BMW 3.0 d turbo aspirated
     

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  6. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    Can't see much from the video.

    Maybe you are talking of closed circuit heat exchanger?

    Wet exhaust means metered spraying an unlimited supply of water on the exhaust before it is discharged.

    It takes some engineering to do that that is why I gave you the leads on Vetus and Volvo. Things like heat, cracking, water ingestion can be solved and I have outlined the ways.
     
  7. MihaS
    Joined: Jan 2011
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    MihaS Junior Member

    On the video you can see how he made exhaust and intake manifold together. I will make the same process but just exhaust.

    I know that wet exhaust means spaying water before outlet.

    Ok closed cooling exhaust. Maybe.

    But like i wrote yanmar series 6lp ,havent been exhaust collector cooled with water.I think!?
     
  8. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Most cars and trucks have dry exhaust with common off the shelf cheap tubing.

    The simplest (if it can be fitted) is to run the exhaust pipe inside some of the SS fireplace exhaust . This locks together and is well insulated and cheap, its not marine $toopid bucks.

    Remember there are many uses for the heat IN the dry exhaust , drying a hanging locker, heating the interior of the boat , or placing a coil or tank to heat water for instant coffee or tea , or as a true domestic HW source with a bigger heat tank.

    Free energy is always fun!
     
  9. sdowney717
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    Location: Newport News VA

    sdowney717 Senior Member

  10. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    For most boats a std truck mugffler will work fine in a dry exhausr.

    Fir those with thicker wallets that can pay for the sound of silence,

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  11. tom kane
    Joined: Nov 2003
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Flexible metal tubing including Stainless Steel is available and also metal bellows,good for many exhaust designs wet and dry.
     

  12. MihaS
    Joined: Jan 2011
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    Location: Adriatic

    MihaS Junior Member

    Decision was made

    I was on meeting with some welding ing. from Welding institute in Slovenia. I we discous about material to use in this matter ,and he also prefered black steel(use in fireplace).
    Hasteloy is also good but hard to work with it.

    Inox i dont want to use because friend of my, have made them a lot and get all rejected,but he made for mercruiser and volvo gas engines.

    In few days you will get some pictures of making it. Now i draw it and give all parts to laser cuting company.

    Regards

    Miha
     
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