coyoteboy Posted September 9, 2017 Share Posted September 9, 2017 Cracked open a stock backbox this afternoon, been meaning to do it for a while after I saw a US guy had done it but his photos were on photobucket and have been culled. Here you can see the gas path of one half of the backbox... It flows in bottom right (hole facing the camera, partially hidden) and through the "mesh" separator, then out of the pipe on the left. The small right hand pipe is a resonator into a separate side pocket. The opposite is the direct mirror of it. No packing material was in there. Quote Link to comment Share on other sites More sharing options...
scobie140 Posted September 10, 2017 Share Posted September 10, 2017 Not what I expected to see Quote Link to comment Share on other sites More sharing options...
davey_83 Posted September 10, 2017 Share Posted September 10, 2017 much room for improvement obv Quote Link to comment Share on other sites More sharing options...
coyoteboy Posted September 11, 2017 Author Share Posted September 11, 2017 Certainly a bit tortuous but does a good job of silencing, that's for sure! Now trying to decide whether to modify the internals to keep stock look or use it as a fixture to make something better. Probably the first option. Quote Link to comment Share on other sites More sharing options...
veeg33 Posted September 11, 2017 Share Posted September 11, 2017 I think to make it louder, you'll just need to block some of the chamber(s), ensuring the exhaust gas goes straight out. Quote Link to comment Share on other sites More sharing options...
coyoteboy Posted September 11, 2017 Author Share Posted September 11, 2017 (edited) There's no way of it going straight out, it has to go through the mesh wall and contort around several shapes - it's a contorted route because it's not fed through a tubular path, but yes - capping some chambers will reduce the attenuation at specific ranges. Edited September 11, 2017 by coyoteboy Quote Link to comment Share on other sites More sharing options...
scobie140 Posted September 11, 2017 Share Posted September 11, 2017 There is a popular mod on the M3's where they open up their back box like this and re-pipe it so its a straight through, sounds much better Quote Link to comment Share on other sites More sharing options...
coyoteboy Posted September 11, 2017 Author Share Posted September 11, 2017 I think straight through would be a tad too much (might as well just buy short tails) but i might try putting in perf tube and a couple of bends to route it "straight" through, then back-filling with packing. Quote Link to comment Share on other sites More sharing options...
Bikeracer Posted January 16, 2018 Share Posted January 16, 2018 Did you finish the Exhaust? Quote Link to comment Share on other sites More sharing options...
coyoteboy Posted January 16, 2018 Author Share Posted January 16, 2018 (edited) No, I have the parts sat in my garage but I've not had chance to cut and weld yet. I've not forgotten though, so I'll update when I do it. I think what I'll do, for clean flow, is divert the two routes across each other, rather than try to curl round 90 in a short space. Edited January 16, 2018 by coyoteboy Quote Link to comment Share on other sites More sharing options...
GrahameJ Posted January 16, 2018 Share Posted January 16, 2018 Demon Tweeks sell bends and perforated exhaust tubing that may help make the job easier: https://www.demon-tweeks.co.uk/performance/universal-exhaust-parts Quote Link to comment Share on other sites More sharing options...
coyoteboy Posted July 16, 2018 Author Share Posted July 16, 2018 FYI - the mid-box is just a stuffed perf tube. Quote Link to comment Share on other sites More sharing options...
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