emergency exhaust quieting

[BMWChris]

Competing in a rally tommorow in my Midget. haven't had time to get the noise level checked. I think it should be ok but what can I do if it isn't? Is there anything I can take with me to quiet it long enough to get it through scrutineering?

[fastcarl]

if its one or two db high you could try fixing some crosswires at the tail pipe exit, , this can diffuse the gasses and lower the reading,


carl

[speedychrissie]

or stuff some wire wool down the end of the exhaust.

Or if you think it might be a recurring problem you could buy one of these:
http://www.merlinmotorsport.co.uk/p1576/MERLIN-MUF...

[BMWChris]

Thanks for the advice. Didn't need it in the end. As soon as I arrived at scrutineering and heard some of the cars in the que I knew it would be ok. Spent the event driving around with a loud of wire wool in the boot that I had taken down just in case!

[Chris71]

Glad to hear it was okay in the end.

Now it's resolved, can I hijack the thread and ask what people do when noise is a problem?

If I keep hold of the TVR then I'm going to need a job lot of wire wool for sprints and track days I suspect! Many of the other TVR guys have additional bolt-on silencers which seem to do the trick, but I wondered what the pros and cons were.

[Count Johnny]

It's probably worth me making you aware that, for this year, the circuits have been instructed by the MSA to enforce a long standing ([C(b)23] requirement that silencing levels should be achieved without the use of temporary parts.

I was involved in testing at Snetterton in February (with all of 8 cars testing all day) when this came to light and one (of only eight) was excluded until Graham Hathaway had a good old shout.

I'm not saying it will happen every time (and - as discussed at the time - how the f*ck do you identify an exhaust/silencing component as temporary) but....

[Chris71]

Count Johnny said:

It's probably worth me making you aware that, for this year, the circuits have been instructed by the MSA to enforce a long standing ([C(b)23] requirement that silencing levels should be achieved without the use of temporary parts.

I was involved in testing at Snetterton in February (with all of 8 cars testing all day) when this came to light and one (of only eight) was excluded until Graham Hathaway had a good old shout.

I'm not saying it will happen every time (and - as discussed at the time - how the f*ck do you identify an exhaust/silencing component as temporary) but....

That's a very good point - I never noticed that before.

I guess something like this...



...is fairly obviously bolt-on (hope Wyn doesn't mind me borrowing his photo ) but if there's a silencer in the place it's designed to be - albeit a bigger one - I reckon it's okay.

I know what you mean though.

[deviant]

I was always under the impression that wire wool just get blown out of the exhaust in the form of a shower of sparks the first time you give it any decent revs?

[Count Johnny]

Chris71 said:

I guess something like this...

That'll do it...

[99hjhm]

deviant said:

I was always under the impression that wire wool just get blown out of the exhaust in the form of a shower of sparks the first time you give it any decent revs?

Don't know about the sparks, but it won't last long.

I know a guy who filled the silencer with aluminium wadding, ended up shooting a red hot peice accross the pits coming down the straight at Castle Combe.

Edited by 99hjhm on Wednesday 27th May 21:36

[GreenV8S]

Count Johnny said:

It's probably worth me making you aware that, for this year, the circuits have been instructed by the MSA to enforce a long standing ([C(b)23] requirement that silencing levels should be achieved without the use of temporary parts.

What's that reference to? I can't make sense of it as a blue book reference. I guess it's something specific to racing and unlikely to affect other events - I can't see why the MSA would have any say in technical regs for track days and so on.

[Matt_N]

I may have heard of a few cases where people have adjusted their rev counters to show a lower rpm reading, eg 4k rpm on the clock is only 2k rpm.

[fieldl]

Page 152 3rd bullet point from the end of article 23:
Temporary silencers, by-pass pipes or the inclusion of temporary parts to achieve silencing requirements are prohibited. Officials may refuse to carry out sound checks on vehicles utilising temporary parts in exhaust systems.

Never knew that was there. No definition of temporary mind.

[speedychrissie]

GreenV8S said:

I can't see why the MSA would have any say in technical regs for track days and so on.

I agree. I know the blue book is big and not always easy to understand but I believe that trackdays are not governed by the regulations placed in it. Particularly regarding the regulations in section C as there are lots of things that are apparently mandatory which definitely do not occur at track days.

I may be wrong though.

ETA:
The blue book definition of temporary is (end of page 65):
"A part that differs in type or material from that normally used on or that which has a short useful life expectancy"

that is very open to interpretation, but with the huge variety of racing exhausts I think an additional silencer would be fine as I would say that wire wool has a short useful life expectancy whereas a bolt on silencer does not. So even in proper racing I think you should be ok to have a bolt on silencer.

Edited by speedychrissie on Thursday 28th May 19:36