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Thread: Pre-cat pipe = more noise?

  
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    Pre-cat pipe = more noise?

    Having recently purchased a Zafira Gsi, I have started the modification process in an attempt to make me feel less unhappy about having to let my coupe turbo go. I loved the exhaust I had on the coupe so went for an identical set up on the Gsi plus the addition of a pre-cat pipe.

    Even with a centre silencer built in, it seems so much louder than the system on my coupe. I have heard rumours that fitting a pre-cat will make a system louder, and can change tone higher up the revs - is this the case?

    It seems quite boomy up to around 3-3.5k RPM, then gets higher and rather tinny like an M3. Has anyone else noticed this?

    Is it worth getting a larger centre silencer fitted, or is it just a case of putting up with it after fitting a pre-cat?
    - 2004 Vauxhall Zafira GSi - Silver, work in progress..
    - 2003 BMW 325ti M Sport - Silver, 18" CSL wheels in matt anthracite, Eibachs, Full red leather

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    Replaced my Pre-Cat 2 weeks ago, and i have noticed it sound a little bit louder than before probarbly because it hasnt got to travel through that filter thing that is in the Pre-Cat.
    But u can tell the BHP has gone up a bit
    That Makes Alot Of Sense - Alot Of Nonsense

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    put up with it!!

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    Yep, deffo makes it louder.

    I noticed this afterI had put a cat back on my Mk4 SRi Turbo - made it that bit too loud!
    2006 Astra VXR on 19's in Arden Blue
    ExhaustsUK Catback, Eibach Sportlines, DS Ultima, Roose hose kit, Forge recirculating dump valve, Full self modded SMD conversion

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    lee gsi's Avatar
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    Mine is a bit louder and a different tone but its only noticable when your booting it.
    The truth is always the truth even if you haven't realised it yet...

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    It is quite a bit louder than I was hoping for, but my biggest problem is the change in tone higher up the revs as it's quite tinny and makes me feel paranoid that people will think it sounds like an old banger.

    Is this change to a 'tinny' tone at 3-3.5k rpm normal with a pre-cat?
    - 2004 Vauxhall Zafira GSi - Silver, work in progress..
    - 2003 BMW 325ti M Sport - Silver, 18" CSL wheels in matt anthracite, Eibachs, Full red leather

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    Are you sure its not leaking?

    Mine sounds nice and not tinny atall
    The truth is always the truth even if you haven't realised it yet...

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    what exhaust did you go for

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    Custom 2.5" powerflow cat-back system.

    But surely if it was leaking you would be able to hear it lower down the revs as well? Sounds normal up until around 3k rpm?
    - 2004 Vauxhall Zafira GSi - Silver, work in progress..
    - 2003 BMW 325ti M Sport - Silver, 18" CSL wheels in matt anthracite, Eibachs, Full red leather

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    Quote Originally Posted by Patrick View Post
    Custom 2.5" powerflow cat-back system.

    But surely if it was leaking you would be able to hear it lower down the revs as well? Sounds normal up until around 3k rpm?

    You see thats the problem all the powerfow/long life boxes are generic so they dont tend to sound that great should of got a Miltek/Jettex/mongoose as the quality would of beeen miles better and definately the sound would of been much more tastefull.

    As you already have the system take it back and get them to change the packing in the boxes which will in effet change the sound/tome.

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