Track days - noise - back firing on the over run

[dern]

Hi,

According to the previous owner my car will measure roughly 92db on the static test and has been round bedford so is pretty quiet for what it is.

However, it can occasionally backfire on the over run. Is this likely to cause me any difficulties or does it depend on the circuit/airfield?

Thanks,

Mark

[Steve H]

Driveby meters tend to be placed where you are on maximum acceleration so you'd be unlucky to have a problem with overrun noise.

[Mastodon2]

Steve H said:

Driveby meters tend to be placed where you are on maximum acceleration so you'd be unlucky to have a problem with overrun noise.

True, but I recall reading on one of the Type R owners forums about a guy who set off a noise meter with his pops and bangs on the over run, I think it might have been at Cadwell park. He had a Civic Type R with a Spoon N1 exhaust and a Spoon silenced centre pipe, and just made the 95db check with his exhaust bung in, but when he lifted off the throttle at speed the predictable bang from the exhaust was even louder than without the bung, I think he registered 105db or something on the way past a noise meter. Anyway, despite getting through the static test and getting a few laps in, eventually his lift off bang tripped the meter and he was black flagged pulled off the track.

[Steve H]

Last time I was working there (last year) they didn't have driveby at Cadwell. Possibly if it was really noisy on the way into Hall Bends he got pulled as they would hear it very clearly from race control or maybe it was another circuit but I can't think of any where you would normally overrun close to a meter

[Mastodon2]

I did a bit of googling and I can't find the thread about the guy getting black flagged for his pops and bangs, but did find quite a few threads of people stating that bungs amplify pops and bangs due to the effect of increasing the back pressure.

It could well be an effect of the gear changes though, I've just fitted a fully unsilenced exhaust to my Civic Type R (which would never pass a noise test in this country in a million years, even on a "loud" session that some places have), and when changing up towards the redline as I clutch in and close the throttle for the upshift it lets out a sharp bang or a loud bass pop, which spikes the volume output. I'd imagine if I was running a bung and just about passing near the drive by meter, if I had to shift up above 6800rpm near the meter the noise on the shift would get me pulled from the session. Irrelevant anyway since I've no interest in tracking my car, but an interesting bit of acoustical physics nontheless.

[mad4amanda]

Its still classed as nuisance noise and if its loud and persistant it will normally be black flagged at brands .

[mmm-five]

I remember being told to slow down and not slide through one of the corners (just after the 'pit/paddock' exit) at Prestwold Hall as the noise from the tyres squealing was over their noise threshold.