I'm going to borrow a noise meter from the very nice lads at SWTOC as I want to do a track day next month at Keevil.
My car only just passed the SVA (shouldn't really only rev'd to 6K). It has to be under 100 DB at 0.5m.
I have a blade with an MK exhaust.

If it's to loud will restuffing reduce the noise and if so which material and where?

Ive got 'till the 14th March.

Anyone else going?

If you re-pack be carfull you dont put to much in, you want it to soak up the noise not bounce it about, if you pack it too tight its like claping your hands in a "ginnle" it sounds louder. Most track days are "drive by" rather than a static test (a lot do say they will test it static on forms but don't)
You can get one of them "decible eaters" cheap as chips on ebay stuffed up exhaust and held in with one bolt, but ive found them not too work for me unless iv'e shoved soom wire wool up 1st and used the "decible eater" to hold it in there, all that said sort it before you go, nothing worse than turning up for a couple of laps then black flag, was at Donnington Sunday, they where keen 98dba drive by with plenty of black flags to be seen.

what rev counter you got ? Iv'e sneaked thru static noise tests by altering the number of clys setting on a rev counter, making it read 6000rpm when its actually doing less, crafty but it works....

[Edited on 17/2/05 by Jon Ison]

[Edited on 17/2/05 by Jon Ison]

The noise monitor at Donington is one of ours!

It's not sited in the best place though which makes it worse.

Ours at 7000RPM was 104db - not good, equivalent setup. Chances are the wire wool jobby will blow out and/or restrict it to much. Better to reduce the bore of the exhaust but this also has the same effect as a brick under the LOUD pedal... May be worth repacking but as the Isonmaster says - too much will act as no packing at all. Too little and the same effect... good luck. Sounds like trial and error to me...

Northy, go get it sorted...

Yep just had it tested 104DB at 7700 revs
That being 3/4 of max revs ish.

Just had a word with Performance exhausts at Collumpton, will go up there and see what they can offer. I want to get a boss put in anyway for a Lambda sensor for rolling road tests.

Some years ago I had a play around my old Opel Manta (with 16v XE engine on throttle bodies) with a sound meter..................the exhaust was consistently around 100dbA, (2.5" system with two big silencers) but the induction noise was over 103dbA!!!!!!!!!

quote:

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Originally posted by Jon Ison
Northy, go get it sorted...

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quote:

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Originally posted by Dave Ashurst
I think drive-by noise measurement is quite different to the SVA exhaust noise test. Just wondering, are the results comparable?

I mean, I wouldn't want to spend much on silencing the exhaust (and retuning the engine to suit) if it wasn't necessary.

ISTR in a drive-by noise test there's an array of microphones? parallel to track, 3.5m from vehicle?

Don't they measure combined noise from:

tyre/road
wind
intake
exhaust
mechanical noise (e.g. whine from a straight cut gearbox can be significant)
screaming passenger..
etc

I suppose 104dBA at 500mm from the exhaust would be less at 3.5m?

Is it worth checking that first?

[Edited on 18/2/05 by Dave Ashurst]

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Or one of these:
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quote:

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Originally posted by Dave Ashurst
Aha, I see.

I probably won't understand the answer! but sticking a microphone up in the air on a pole seems a bit random; what does it measure?

How do you know from that how loud any given car is? Isn't distance from the source an important part of the calculation?

If there are 2 or more sources of noise doesn't that confuse the reading?

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