New Pipes

[honan]

Hi guys, i have just had a new catback built today.

3inch stainless with A M Performance 3 inch resonator and 4 inch twin pipes at the rear.

the twin pipes are internally baffled, kind of the same way cannon mufflers are.

The car still has a 3 inch dump and front on it.

The issue is now with this set up is louder than my setup with just a cannon..it sounds 50,000 times better BUT for street its a tad to much.

was thinking a 3 inch muffler box that would bring it down a little but not to an overly quiet level

or should i replace the gutted cat with a 100cpi metal cat.

really need this effin exhaust finished

Edited February 17, 2011 by honan

[75coupe]

twin 4" pipes out the back... so is it purely a cosmetic exhaust?

[The Bogan]

You need a rear exhaust box with some volume to it, if its those exhaust tips that are not much bigger than the pipe they really do nothing in reducing the DB.

A straight through 3.5" rear box with the lenght of 450mm, width of around 250mm and a height of around 150mm fits and keeps it just legal, It does on mine anyway

Mark

[honan]

the twin pipes are still mufflers, i just want a muffler of some sort in the centre.. i got the twin 4 inch muffler pipes because they fit the standard cutout in the rear bar

[The Bogan]

I have one in the center as well, 3.5" about 350mm long and 150mm round, but it still needs the box at the rear to keep the DB down.

Mark

[R31Nismoid]

Well i'd argue the "pipes" are mufflers, i mean a tiny bit of baffle does sweet fk all, so does the resonator.

CAT realistically wont drop the noise much either.

You need to either put a decent mid-muffler in, or live with it

[honan]

thats what im saying...what mid muffler would you recommend? i dont mind if its a little above the limit..but this is  a bit to loud...queit at highway speeds, just on accel.

[R31Nismoid]

Define "quiet". One persons version is not the same as another.

Quiet according to the law is 90dB @ 4700rpm no load, this requires basically 2 of the bigggest mufflers you can fit for a 3" or larger exhaust.

Now the mid muffler is going to be nowhere the same in terms of effect as its smaller than the rear will be and you basically have 2x4" noise amplifiers

So putting in the bigger possible mid-muffler is realistically your only choice.

I'd take a stab @ it probably being at least 96-98dB @ 4700rpm no load, which is massively louder and will realistically never be "quiet" and it will always drone etc as thats the effect of 2x4" outlet pipes, it might even be more even with a mid muffler.

No one can tell, and as i said - no two persons definition is the same.

[honan]

all good now, Andrew At AM performance have sorted me out with a similair setup to there 33

cheers!