Silencing the silencer

A little real work; longer days are back with the clocks changing but its still pretty cold in the garage;

I took another look at the silencer & the wire wool down the pipe approach - my first prototype was promising but needed some way to secure it - concept demonstrated in this picture - a wire from the bottom of the can out through the tailpipe which could be secured to the wire wool cage. The challenge was not knowing the internal design of the GBS silencer & knowing there would be a central holed pipe to negotiate:

I drilled through the centre of an existing rivet and managed to feed a short length of steel cable through the hole, through the central silencer pipe and out through the tailpipe.

Test run with my prototype caged wire-wool extended - excellent blueing of the wool after some engine runs, but overall this was just too complex - time for a little simplification:

I decided on a much smaller cage which would simply stop the wool being pushed out - internally the wool bundle is held in the central silencer pipe anyway. This little 2" long cage grabs the end of a 12" long wire wool bundle and follows it into the pipe secured in place with the wire through the bottom drilled out rivet hole:

Cable secured underneath with a self tapping screw:

Just the tip of the wire wool visible in the tailpipe, hopefully its far enough back to let the IVA emissions probe insertion - checking with them they need 3" for the emissions probe so I should be fine:

Finally tidied up with the cover back in place - I also added a strengthening bracket with 2 rivets at its mounting point:

Update - This didn't really work at all - quietened the exhaust ok, but means the emissions are impossible to test because the emissions probe will no longer fit in the exhaust. Ultimately passing the sound part of the IVA was down to making sure the car wasn't near any buildings so no sound reflections.