curiousity got the better as usual...and beleive me it was a tight muff to open...dirty too!
so heres a few pics to let ya all know how your C36 muff is constructed and why its so conservative...

Anyhow the plan is/was to upgrade the pipes to a larger diameter(3")....unfortunately,theres little room!

the muff is made up of three chambers...

heres a pic of the rear chamber...showing the 2 1/4 inlet which heads through the centre chamber to the front,this part was packed with fibreglass...






heres the front chamber which does not have glass packing...from this you can see exhaust gas enters the front chamber via the 2 1/4 tube and exits via the two smaller pipes above...it then goes back through the centre chamber to the rear and then returns through the center again to the front chamber and out through the tips...the center chamber is glass packed and all tubes passing through are perforated... its also difficult to remove due to it being weld in place once slipped inside the muff...






before the gas leaves the muff there is yet another perforated tube inside each Tip....





So with all these bends,reverse flow and tones of perforation...its no wonder its so quiet!...but with a tubine in line we should be able to loose alot of this and still be smooth and deepish....
next step looks like i'll build a 3" custom item with a similar style,and with out reverse flow!...

Paul