exhaust noise

[iwsh]

Hi

I have a Merlin with 2lt Pinto engine plus piper cam and stage 3 head - some italian sounding carbs as well de ortio or something !!Anyway, it has a very loud exhaust which i would like to quieten but not spoil the performance. Silencer is under the running boards . Any ideas please - also any hints on general sound proofing - wife complains !!

Ian

[tribbles]

I think that whatever you do to make it quieter will impact performance by some degree.

Jetex make some decibel inserts (www.jetex.co.uk) - I've not used one, but they look like they fit inside your current pipe, which means that it'll need to be cut and re-welded, but doesn't mean any large extra boxes.

Not sure how quieter they make it, nor how much power you'd loose either. However, I may end up using one if my Aeon doesn't pass the SVA because it's too loud.

[knightly]

I used a decibel insert at Donington on a track day, as I got a warning from the noise meter people - and it reduced the noise a treat - was speaking to someone recently and they measured the before and after noise on a ff2000 single seater, which coincidentally runs a pinto! and they noticed a 3db noise reduction - both me and the bloke agreed - we could not notice a reduction in engine power - so yes they work VERY well......you dont need to weld them in - I bolted mine in place with a single M6 .....they are dirt cheap at about a tenner each......you may need to flare the end out a little with the ball end of a hammer, in order to ensure its a good fit inside your tail pipe.......for those of you that dont know about noise - the difference between say 95 and 96 decibel is double the noise - its measured on a funny scale, so 3 decibels is actually a very large reduction in noise!

[Avocet]

I think the best way of reducing noise is with the volume of the exhaust system. If you can fit enough silencing volume under the car, you should be able to keep it quiet without sacrificing power. Big silencers with lots of packing all round the perforated tube(s) inside seem to work best - ideally ones with curved (cylindrical or at least oval) casings so that they don't "pant" or "ring" with the gas pressure fluctuations are ideal. Major manufacturers can get away with funny-shaped flat-topped ones but only with lost of stiffening ribs pressed into the casing.