More power = more NOISE! If you have converted your S1 to Honda or Duratec power and intend to track the car you will be failing the drive-by decibel limit. This H2 silencer (2 Helmholtz noise-cancelling chambers) is a pain to build (although round silencers are not as bad as the oval V6 H2 silencer!!). I can only fit the 7"dia (178mm) silencer in the limited space but feedback from customers say it is enough for most circuits. There is always the option of a Silenced De-Cat Pipe (SDCP) or a slip-on tailpipe add-on silencer - that's how crazy this noise-averse society is becoming.
If you study the images you can see the internal welds on the baffle-plates forming the chambers. Usually, the perforated core-pipe runs from inlet end-plate to the outlet end-plate. This makes for a strong unit. Break that run with a couple of chambers and you need to reinforce everything! Also, if you have an open chamber you invite resonance (dronnnnne) into the exhaust. Cheap, rigid exhaust mounts helps it travel down the Aluminium chassis legs right into the cabin - not good.
The silencer body is double-skinned to counteract any tendency to drone and the centre-section is packed with Acoustafil ZT-1.
I TIG-weld all the pipework for integrity and yes, it looks good too. The tailpipe module is a favourite of mine. All in all, a time-consuming and expensive build - but it works.