Quieting an "Ulster" Exhaust

[Charles Levien]

I remember a time when the louder the exhaust, the bigger the grin!

yes, let’s celebrate a bit of noise before electric cars take over. There’s nothing like hearing the engine get that harder sound as you get going on a good road and then a lovely burble on the overrun. And all this without doing much more than 60 mph.  Above that I can’t hear much but perhaps that’s just me.

[Chris KC]

As Ian said, there isn't a lot inside the 'silencer', it's just an empty box with the stubs of the inlet and outlet poking a little way in. I made one for myself last year and at idle yes, it does sound a bit like nuts and bolts shaking around in a tin.

I suppose you could make a new expansion box with some internal structure to damp out this sound, but I think it would require a lot of experiment with uncertain outcome and possible unwanted side-effects.

[jansens]

I made a Brooklands style muffler for my special and yes, they are basically an empty box. I ended up changing it for a commercial muffler (for an 850 Morris Minor or Mini - smallest they sold). I changed because I wanted the exhaust to run under the car not along the side and also because I didn't like the sound of the Brooklands. It did sound harsh and tinny. I may have made it too small a volume though.

The other thing I did when I changed was I made rubber mounts for the silencer and rear pipe. That actually made a big difference. When hard mounted I got a sort of resonance through the car from the exhaust. Is hard to explain and was almost more a feel than a sound but it made the car sound and feel smoother when I rubber mounted it.

To make the mounts I used steel strap and instead of just drilling a mounting hole and hard bolting it to the chassis I enlarged the hole to be a tight fit around some thick wall rubber hose (I used modern 5/16th oil hose) that slides over the bolt. I made slightly larger round rubber washers from some 1/4 inch rubber sheet (ute bed lining stuff) to go either side of that. I made four of these, two with 5/16th bolt sized holes in the middle and two with a larger hole to match the OD of the rubber hose.

The oil hose was cut to length so it fitted through the mounting steel strap and extended 1/4 inch either side. Next the rubber washers with the large hole gets put over the protruding ends of the oil hose then the rubber washers with the bolt size hole on the top of those. Then some flat metal washers and nuts sandwich it all together.

The idea being there is no metal to metal contact anywhere to transmit sound/vibration. That seems to have worked really well. It's rigid enough not to move but stops the body, which is just a big aluminium box really, from resonating. Not sure how well it will hold up over time.

I should note this has all only been tested in the garage since the car isn't on the road yet!

Simon