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  1. #1
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    Downpipe + full exhaust

    Hi everyone, I need some help. I posted this in exhaust thread, but might as well post it here to get more views.

    Yesterday I hit a lost tire on the highway, it broke my downpipe on the ZJ 5.9

    I would like to replace downpipe and full exhaust.

    I don't have money for DT headers, so I would like to get fab a custom downpipe into a custom 3'' exhaust. What is best downpipe size ? I can get a flowmaster Y pipe 2.5'' inlets and 3'' outet for cheap where I live. Is this a good Y pipe ? 2.5'' downpipes can fit onto stock exhaust manifolds ?

    Also, what are the best parts to get for a complete 3'' exhaust ?

    thank you

  2. #2
    Forum CONDUCTOR Man Z88Z's Avatar
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    You might have to get it custom made if you want better than factory.

    A shop that specializes in performance exhaust should be able to do it - just make sure you tell them what you want, no crimps or crushes, tight bends, etc.

    They should also be able to put together a good 3" exhaust, but it takes a good shop to make a good over the axle pipe without crimps etc. You want mandrel bent.


    I think there used to be a semi performance downpipe offered for these, but not sure if it's still made or how "performance" it was.

    I'd check Summit or Jegs to see if they still carry it. I think you can find full 3" kits on there too.

    There's several different cats and mufflers that will work, although you'll get many opinions on which is better.

    Kolak in our vendors section makes a nice 3" kit btw

  3. #3
    im super special x10radsponge's Avatar
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    I have had custom down pipes made. Email me a x10radsponge@gmail.com letting me know who you are and I will send photos. I love what was done.

  4. #4
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    what is best for y pipe :

    2.25 engine pipe to dual 2.25 to single 2.5 y pipe, then weld a 2.5 to 3'' adapter for 3'' cat

    or

    2.25 engine pipe to dual 2.5 to single 3'' y pipe, then 3'' from there

    or

    2.5 engine pipe to dual 2.5 to single 3 y pipe

    ??

  5. #5
    RallyJeep GO
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    You can get a dual 2.25" to 3" merge. I'd just do that and run the 2.25" pipes down from the manifolds to the merge, and then 3" right into the cat.
    1998 ZJ 5.9 Limited - Deep Slate
    Mods: Big trans cooler, 231 swap, Indy MA-X heads prepped by IMM, Comp 20-744-9 cam, 1.7 HS roller rockers, 52mm TB, Airgap manifold, DT headers and full 3" exhaust, SCT tune homebrewed by me, Martin Saine valve body, B&M tranny pan, magic suspension made from unicorn tears, power steering cooler, lots of lighting mods

  6. #6
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    thank you Sir !

    I too think it's best to get 2.25'' downpipes since manifolds exit in 2.25''.

    For a muffler, I was thinking to buy Dynomax Super Turbo 17744, any comments on that choice ?

  7. #7
    RallyJeep GO
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    People generally like the super turbos, they're not too loud and sound pretty good. I've never run one personally, so I've got no firsthand experience.
    1998 ZJ 5.9 Limited - Deep Slate
    Mods: Big trans cooler, 231 swap, Indy MA-X heads prepped by IMM, Comp 20-744-9 cam, 1.7 HS roller rockers, 52mm TB, Airgap manifold, DT headers and full 3" exhaust, SCT tune homebrewed by me, Martin Saine valve body, B&M tranny pan, magic suspension made from unicorn tears, power steering cooler, lots of lighting mods

  8. #8
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    I ran Super Turbos on my 401 Cherokee Chief and loved them. For casual driving they were pretty tame sounding, even quiet, but when you put your foot down they really opened up... but that was on dual shorties where I needed more muffling, and they wouldn't flow as well as some others on a single exhaust (though probably better than Flomasters).
    On my niner I use the Magnaflo 12589 which I love at least as much. It flows much better because it's a straight-through design, is a little more audible in casual driving, has an almost subsonic rumble at idle, and they absolutely scream like an angry tyrannosaurus when opened up. It's a big muffler, so has a very deep tone that makes the 5.9 sound like a 6.9.
    I'd give the edge to the Magnaflo for the application, but I think you'll be happy with either.

  9. #9
    RallyJeep GO
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    I've got the slightly quieter, split-core version of that Magnaflow on mine (the 12579). It's a center in/out unlike the 12589, so I'm running an s-pipe behind it to line up with the tailpipe. I've also got a Vibrant ultra-quiet resonator in front of it, so it's fairly quiet at idle and in normal driving (barely louder than stock), flows pretty well (resonator is straight through, muffler is a y split, 2 straight through tubes and then a merge). It's really deep sounding most of the time and has a nice howl to it when you get into it.
    1998 ZJ 5.9 Limited - Deep Slate
    Mods: Big trans cooler, 231 swap, Indy MA-X heads prepped by IMM, Comp 20-744-9 cam, 1.7 HS roller rockers, 52mm TB, Airgap manifold, DT headers and full 3" exhaust, SCT tune homebrewed by me, Martin Saine valve body, B&M tranny pan, magic suspension made from unicorn tears, power steering cooler, lots of lighting mods

  10. #10
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    Quote Originally Posted by carlmon View Post
    I ran Super Turbos on my 401 Cherokee Chief and loved them. For casual driving they were pretty tame sounding, even quiet, but when you put your foot down they really opened up... but that was on dual shorties where I needed more muffling, and they wouldn't flow as well as some others on a single exhaust (though probably better than Flomasters).
    On my niner I use the Magnaflo 12589 which I love at least as much. It flows much better because it's a straight-through design, is a little more audible in casual driving, has an almost subsonic rumble at idle, and they absolutely scream like an angry tyrannosaurus when opened up. It's a big muffler, so has a very deep tone that makes the 5.9 sound like a 6.9.
    I'd give the edge to the Magnaflo for the application, but I think you'll be happy with either.

    thank you for detailed reply.

    Here, Dynomax is half the price of Magnaflow, and I want it to sound quiet while driving in town, and some sound when I smash it, much like stock exhaust.

    I'll give it a try and if I don't like it, I'll change it next year.

    thanks again to everyone for all answers ! really appreciated.

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