Exhaust advice

[4packet]

After a bit of exhaust advice please guys. 

Have just had a stainless steel exhaust fabricated for the car (Stock LS3) with the following layout:

Stock 2010 Camaro manifolds
2-1/2” downpipes
2 very small silencers on each side before the diff.
2 x 2-1/2” pipe leading to a single dual rear silencer.

Each bank is completely separate until the rear silencer

Haven’t had a chance to properly test it under load and high revs, but first impression is that the idle on initial start is a bit boomy and a little loud. Blipping the throttle seems to make it a little smoother, but it still seems quite loud. I say ‘loud’, relative to the strict noise limits we have on UK circuits.

Would an H or X pipe make a significant difference to the way it sounds and overall noise level? Would it reduce/eliminate the ‘boomyness’ at idle? I’m not that bothered by any potential power/torque increase, just the sound quality.

Thanks in advance

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[4packet]

No-one have experience of the effect a link pipe has on a dual exhaust?

[rex388]

H pipe would get rid of the choppyness. And will also reduce noise.

[gnx7]

Magnaflow makes a nice Xpipe for around $100.  That will help with low end torque and cut the noise down a bit.

[Grr]

...

[Jordan Innovations]

^^^ as said, an X-pipe can help with that (a little).

I'm surprised that you think it's loud, since I've done two systems that are very, VERY similar to yours (one on a cam'd LS1 car, another on an E-rod LS3 car) and they were both very quiet with resonators on each bank and a dual-into-dual muffler.  Quiet enough that the customers wanted to remove the resonators lol.

Start with an X-pipe, positioned just a couple inches short of one 'header primary length' after the collectors (if you have 32" primaries, put an x-pipe 30" or so behind the collectors) and you should get a nice bump in torque in the mid-range as well as a smoother sound.

[4packet]

Thanks for the replies guys.

Went back to the exhaust fabricator and discussed some options. It’s OK on cruise and only a little louder than ideal on load. The main issue is the boomyness on idle which also shows up on load at low revs etc. It measures about 95/96DBA at 4900rpm, 0.5m 45deg from tailpipe. This is a typical measurement for trackdays in the UK.

Plan is to get an H pipe fitted and assess from there. Other option is to play with resonator tubes or fit a rear silencer with a larger cross section.

[largeorangefont]

If your trying to hit a noise number I'd go straight to bigger resonators.

[Chuck78]

Try one of these:
http://www.magnaflow.com/02product/shopexd.asp?zone=main&id=11429
Its an x-pipe and extra muffler in one.  I have used one under a FD before and it tucks up nicely.