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Thread: what bhp from a backbox on a mk5?

  
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    dunkz2006's Avatar
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    what bhp from a backbox on a mk5?

    just speaking to mate and he is thinking of a powerflow backbox on his 1.6vvt mk5 astra what sort of bhp increase should he expect? about 5bhp? and about 10bhp on a full system?

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    mania's Avatar
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    I would have thought 5bhp for a backbox would be a bit optimistic... but really have no idea .

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    Probably wont see any power/bhp increase just different sound tbh
    Astra coupe turbo 280bhp-sold
    BMW E60 5 Series M Sport

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    Pah...

    I'd say a full catback may see 5-10bhp, sort any relevant airbox mods and you may see 15+ total over manufacturers figures. My Z16XE rolls 19bhp up on the standard 98bhp with catback exhaust and airbox mods only, plus similar gains on the torque - 131ftlbs vs the OEM 113ftlbs figure.

    All depends how restrictive the OEM exhaust system is on the MK5's really though.

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    rizo's Avatar
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    as above you wont gain any performance gains, if you do it will be minimal.
    Astra VXR - Arden Blue, Diamond cut 19's, Cruise Control, Debaged, Folding Mirrors, CD70 NAVI and CID + Aux-In, Factory Bluetooth, Piano Black Interior Trim, Full Milltek Unresonated Exhaust

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    SXT's Avatar
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    tbh the backbox only muffles the sound (sure there will be a wee bit of restriction in there - but not alot) get shot of the centre silencer... thats where the most restriction bar the manifolds are in vauxhalls, or so i have been told, by my other vauxhall chums!

    1-3 for backbox
    maybe 5-8 on catback

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    yeh pretty much what i thought guys was just sort of clarifying it for a friend

  8. #8
    fdrightup
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    Quote Originally Posted by SXT View Post
    tbh the backbox only muffles the sound (sure there will be a wee bit of restriction in there - but not alot) get shot of the centre silencer... thats where the most restriction bar the manifolds are in vauxhalls, or so i have been told, by my other vauxhall chums!

    1-3 for backbox
    maybe 5-8 on catback
    had the same problem on mine where the centre box had 3 compartments all i did was use a golf/jetta gti box vk202 and this has a straight though baffle type design and the inside diameter of the baffle is 55mm, but some times just changing the back box slows down the engine then you have to put the system back in balance ie more inlet pressure

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