Sidepipe/muffler diameter

[Ant]

I am starting to build my sidepipes, and have room for about a 22" long muffler and 10-12" long 3.5" turnout pipe! Have some 3" perforated tube organised, I maybe better to go to a 4.5" diameter sidepipe case for more noise reduction, that leaves 3/4" all round inside for sound proofing material over a 4" muffler with 1/2" room for glasspacking, so I wonder if the extra 1/4' of glasspack will actually make a difference if I went to the larger 4.5" tubing, and I guess the larger the tube the uglier it gets! The benefit maybe in slowing the gas flow down with the larger tubing.

For extra noise reduction, I have seen to good effect 3-4 small perforated tubes same length as the 3" tube, used as a removable baffle, apparently this makes a significant sound reduction, but should allow me to do a small bit of town driving!

[Don]

AJ, with the 4.5 " case, might want to check the clearance of the case to the body, determine if heat might have an impact on the paint. Not knowing the regulations in New Zealand, space required for heat shields ?

When my side pipes were re-built, I used a 4" case. Also considered how far out the side pipes would be away from the body for entering and exiting.

[Ant]

Don,

We are required to run heat shields here in NZ, there is not a lot of detail as long as you have them on for the certification. The clearance to bodywork we have allowed for, and as you have mentioned the larger diameter can be an entry/access issue. I guess keeping everything snug and out from the body a good 1" or so is better that some rubbish drums on the side!

[Aussie Mike]

Hi Ant, All of the pipes I've built use 4.5" tube for the muffler body with a 3.5" collector and 3.5" tip. I reckon it looks good and gives room for packing.

I normally use 2.5 perforated tube for the baffles. My shorty sidepipes are just to loud for most tracks so I've got to build some with baffles for the Nationals. these will get 3" perf tube.


Cheers

[Ant]

Mike,

I reckon the 4" looks a bit small, and for the sake of 1/4" closer and 1/4" further out its not an issue, I hate the look of big mufflers, but everyone seems to go 4" which brings me back to the burning issue "is the 4.5" quieter than 4" with the same 3" perforated tube?

I phoned an exhaust outfit today and they said all the bullit style mufflers with 3" internal tube are only 4" OD, I guess the manufacturers only need the 1/2" around the tube for packing, as that quietens more than size to slow the gas flow!

Will look at your gallery to see a 4.5" sidepipe!