works_team

Reviving this thread. I now had a chance to go at a tracknight (6-8pm) at Spa. Black flag is over 95db.

I thought I would be ok with the unsilenced valved exhaust.

OEM 718 GT4 EXHAUST (EU) - 91.1dB
JCR TITANIUM SILENCED VALVED RACE PIPE - 94.5dB
JCR TITANIUM NON SILENCED VALVED RACE PIPE - 95.1dB
JCR TITANIUM SILENCED VALVED RACE PIPE / JCR TITANIUM OPF DELETE - 97.5dB
JCR TITANIUM NON SILENCED VALVED RACE PIPE / JCR TITANIUM OPF DELETE - 98.1dB
JCR TITANIUM SILENCED VALVED RACE PIPE / JCR TITANIUM OPF DELETE / JCR INCONEL RACE MANIFOLDS - 107.4dB
JCR TITANIUM NON SILENCED VALVED RACE PIPE / JCR TITANIUM OPF DELETE / JCR INCONEL RACE MANIFOLDS - 108.1dB

They got me at 103db (!) after an hour or so and I was thrown out of the event.

Any suggestion as to what could have happened here?

Reedy

With them reading 103dB, my guess is in your scenario, the silenced race pipe would not have made a difference. That said I have driven at a local track that is notorious for sound violations (95dB limit) with my JCR silenced race pipe and have not had any issues. I have asked them if they are able to get a reading of actual noise levels rather than just being told if we go over but they are not able to do so.

Do you know where the sound meter is at Spa? If it's near the pit building then it's probably eating all of the echoes and reverb from the grandstand and surrounding hills. Atmospheric conditions, wind conditions and ambient noise will all factor as well. I know some people who will drive for years with the same car and all it takes is for the wind to change on the wrong day at the wrong time and all of a sudden they get sent home.

I think JCR has done their testing at Silverstone and the acoustics there will be somewhat different. The sound meter will be a different distance, at a different angle and your car will probably be in a different gear at a different part of the rev range, travelling at a different speed. Acoustic stuff is notoriously difficult to standardise and replicate.

Heck, I have seen guys get done for 95db in a standard toyota echo due to nothing more than tyre squeal.

works_team

Thanks - this all make sense (although a little frustrating I must say!) I know there is one near the start/finish line, where I suppose the surrounding walls could create some resonance. There is another one in the descent towards the « Bruxelles » hairpin. And I think I have heard that there is a last one towards the end of the track but not sure where. Thinking about it, I had a real moment at Blanchimont at high speed (all my fault, probably too much entry speed and not enough
throttle mid corner) and the tyres made the noise they do when you know you are very likely to crash - could be it that got me caught!