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Has anyone done this yet? I have my car booked in to get the back box removed and replaced with a straight pipe with twin tailpipes. I don't want my car to be to loud and I presume it will be fine as there is the cats and centre boxes which should remove most of the sound

Any opinions greatly appreciated

Thanks Buster
 

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Well It'll be louder no doubt about it.
Most people just get rid of the center silencer not the back box...
 

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Think you will find that is the main silencer .. :(
 
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The Cats will do bugger all in reducing noise, and the mid-silencers are small. The back box does most of the muffling. If you leave it off your exhaust will be very noisy, possibly not passing your next MOT.
 

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Cats help silence the noise.
As mentioned, the rear silencer is a major component in reducing noise.

Cats plus mid silencers should keep noise within limits but don't expect it to be nice.
 

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Hello I'm thinking of doing this too; why would it lose power?
It's best to think as the induction system + engine (valve timing, ignition advance) + exhaust as a pulsed gas pumping system where any change will affect results. Changes to pipe diameter or length and/or backpressure and resonance effects all affect the efficiency of the exhaust side of the 'pump'. Since the 'pump' must operate at variable gas velocities and pulse frequencies it's easy to introduce uneven efficiency that shows up as 'flat spots' in throttle response. Simply changing the volume and gas path length of the back part of the exhaust will tend to move the powerband higher up the rev range. If the stock exhaust volume and length is designed to be most efficient at say 5,000-6,500rpm and the modifications shift that to 7,000-8,500rpm it's not really helpful for power.
 
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