CAT DIAMETER!!! Straight Through Side Exit

[GPGP]

Why does the standard CAT on a 1litre micra have an exit bore of around 70mm when the exhaust connecting to it has a much smaller diameter (around 30mm). There is also no taper to the smaller exhaust pipe!!! This will be harmful to exhaust exit speed!!! I have just connected a side exit straight through exhaust from the cat back and was surprised at the size of the cat compared to exhaust.

Apart from a back box, is there any way of quietening the exhaust down??
I heard that putting a series of small holes in the exhaust will quieten it down??

 

[Alienfish360]

a cat will make it quieter, and inline silencers

 

[Swiper]

I heard that putting a series of small holes in the exhaust will quieten it down??

i would've thought this would make it louder as the exhaust will blow.

 

[Alienfish360]

it would, unless wrapped in exhaust wadding and then sealed with a bigger box, lol

 

[K10Daz]

If its straight through then thats why its so loud because there are no baffles to quieten it down!

 

[Ian]

Why does the standard CAT on a 1litre micra have an exit bore of around 70mm when the exhaust connecting to it has a much smaller diameter (around 30mm).

because then nissan only need to make 1 cat for all of their cars and not a seperate one for each car which would cost more money.