Rear silencer design

[andyiley]

After a successful cat-removal on my e36 328 track car, which only liberated a single db I am next going to remove the massively heavy rear silencer & replace it with a couple of generic stainless absorption silencers side by side welded on to the back end where the silencer is.

My question is around sound levels (yes I know no-one can predict what it will end up as) and what is best for keeping sound levels down to reasonable levels?

eg. should I go for as long as I can fit, as large a diameter as I can fit, or the greatest overall volume I can fit?

I should have plenty to play with as with my decat silencers in place I am only tripping the sound meter at 84db and most TDOs want it to be under 98 - 105db I think.

[DrDeAtH]

I would say a longer silencer body would be better if using something like a cherry bomb.

[andyiley]

Thanks for that, I am thinking more:

Longest -

http://www.ebay.co.uk/itm/251481486995?_trksid=p20...

Widest -

http://www.ebay.co.uk/itm/251482151530?_trksid=p20...

Greatest volume -

http://www.ebay.co.uk/itm/251482298399?_trksid=p20...

[stevieturbo]

All of the above. Bigger is better when it comes to reducing noise

[andyiley]

Thanks Steve, I was kind of assuming that.

[spitfire4v8]

And put it right at the back of the car. absorption silencers are good at silencing a smooth stream of gas, less effective with individual large bangs, so further away from the engine is best, an upstream expansion chamber even better.
If you find you've over-specced on pipe size a useful sound reducing tool is to reduce the exit pipe diameter .. you can play on the dyno putting smaller and smaller exit pipes on until you see a power reduction, then go up one size = best silencing for no power loss.

Edited by spitfire4v8 on Friday 17th July 13:31

[andyiley]

Thanks for that, they will literally be in the last couple of feet of the pipes.