How to make my exhaust quieter

[marT350T]

I have a rear engined car with a single silencer in I need to make quiter for this years TOTB.

How can I do this , I have no room to put in another silencer.

Thanks

[stevieturbo]

Change the design of silencer, fit a larger one in current position....fit a restrictor bung.

Any pics of what you are working with ?

How loud is it at present ?

At SSO, noise levels for the most part were sub 103db, 4500rpm measured at 0.5m, 45deg from the tailpipe

Some of the top cars, are being given a little bit of lee-way on this as far as I know....10 secs or less though.

[marT350T]

Had it measured at 0.5m todat but not at 45 deg straight behind the exhaust. measured 121 db at 4500 rpm !

Cannot fit a bigger silencer so the bung I think is my only option.

Are these any thing facncy or jst a peiece in the tailpipe to reduce the bore ?

[anonymous-user]

Something like this

[stevieturbo]

They can be as crude, or fancy as you want them. Most tend to be a long tube that goes into the silencer with a disc, to restrict, and force an awkward path.
Some are like a Spiral with a tube ( indeed, I use a pair of silencers like this in the middle of my car now, made by Moroso, Spiral Flow )

120db...WTF is it ????? That is seriously loud, although placing it directly in the path of the exhaust, wont help.


FWIW, mine was recently tested at 106db, and mine is fairly loud. I did have a slight missfire at the time, due to a broken spark plug. Havent tested it since, but Im sure it would be a little quieter now.

What car is it, that there are no straight sections at all to fit a silencer of some description ?

[marT350T]

Thanks for the replies I think I will try and fabricate something.

The car is a mid engined polo with a 1.9 20v turbo motor. (see pic below) The exhaust goes under the bumper from right to left which is mostly one big silencer and then exits at left hand side

I was thinking last night that the reading was taken whilst the car was on the rolling road surely this would make it louder than do a static test , wouldn't it ?

http://i176.photobucket.com/albums/w172/mart350t/D...

Edited by marT350T on Sunday 15th June 19:35

[stevieturbo]

Under load would be louder I think.

Can you do a double pass silencer ? Cant really see much from the pics....but looks like there is plenty of room in the back, it the exhaust was routed differently.
Although it would block access a lot

[knighty]

contact JETEX, they sell a decibel insert for about £10, in varying different sizes to suit your tail pipe, it forces the gas into the wadding more and hardly restricts power, commonly used by many track-dayers to get past noise requirements, you can but em from Deemon Tweeks too.

[dern]

knighty said:

contact JETEX, they sell a decibel insert for about £10, in varying different sizes to suit your tail pipe, it forces the gas into the wadding more and hardly restricts power, commonly used by many track-dayers to get past noise requirements, you can but em from Deemon Tweeks too.

When I contacted them they said that the reduction you get will depend on the applicationand will range from no reduction at all to a few db. From what they said there's no way one of these will pull you down from 121db to 100db... 121db is very roughly 6-7 times as load as 100db.

[marT350T]

I have a tvr and at a event I got my cars dbs measured and that was 120.8. db I have come to the conclusion that my polo is no where near that. When i get it back i will do a static test and find out for sure

Edited by marT350T on Tuesday 17th June 07:30

[smckeown]

I believe fitting a smaller tailpipe does reduce noise

[chuntington101]

stupid idea but could you not fit a second silancer after the current one and mount it on the bumper?? is there any rules saying the silancers muct be under the car??

Chris.

[marT350T]

chuntington101 said:

stupid idea but could you not fit a second silancer after the current one and mount it on the bumper?? is there any rules saying the silancers muct be under the car??

Chris.

Chris I looked at this but i do not think it is possible.

[stevieturbo]

It looks like there is plenty of room above/behind the turbo/manifold ??

[CNHSS1]

turbo cars are usually much quieter under load than the static noise test (turbine blades 'chop' up the sound pulses). if you can get it down statically, itll breeze any drive-by test. what about a pair of linked silencers stacked behind the bumper in the boot compartment a la 6R4s (google a pic)? talking of 6R4s, they struggle to get thru noise tests and regularly have to repack the silencers to appease the scrutineers. it seems that because the silencers are close to the headers, the gas pulses are quite fierce and blow the silencer packing out more readily. im guessing (someone clever will have the technical reason) but the further the silencers are from the engine, the 'softer or less aggressive ' the gas pulses and the more constant the flow which doesnt disrupt the silencer packing material as easily. could be your exhaust packing is all blown out. check how the silencers are mounted to the car, rubber mountings should be soft enough to stop transmitting silencer noise to the engine compartment, 'booming and resonating from the silencer. silencer material does effect the sound too, often stainless has a different tone than mild or ally too.