Fabricating a new 3" downpipe

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  1. Fabricating a new 3" downpipe 
    #1
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    ok chaps. Im building my 325i up with a built motor and a custom top mount turbo GT30R for streetability.
    Has anyone got any tips or advices on how best to fab up a new downpipe for it.
    Shall I go 3" or 4"?? I may go to a T3 GT35R sooner rather than later so Im thinking 4" maybe better? and vent to atmosphere or back to the zorst?

    cheers :
     
     

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    #2
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    Suppose the only factors dictating which size would be best is cost of materials and what power levels are you aiming for?

    Coming from Subaru tuning, the majority of these cars are using 3 inch turbo back exhaust systems apart from the higher power cars which use 3.5 inch or 4 inch.

    You could maybe check out what some other BMW owners have done when using forced induction on their engines on www.boostjunky.com which is devoted to turbo'd BM's.

    Kris
     
     

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    Quote Originally Posted by big kris View Post
    Suppose the only factors dictating which size would be best is cost of materials and what power levels are you aiming for?

    Coming from Subaru tuning, the majority of these cars are using 3 inch turbo back exhaust systems apart from the higher power cars which use 3.5 inch or 4 inch.

    You could maybe check out what some other BMW owners have done when using forced induction on their engines on www.boostjunky.com which is devoted to turbo'd BM's.

    Kris
    Thanks Kris

    Thats a useful site and it seems 4" Dp is the way to go for future upgradeability :

    Less Backpressure can only be a good thing on turbo motor anyway
     
     

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