Decibel Rule

[Matt66]

On my 2020 Shelby GT500 my local track dbis 99 my car keeps breaking it mainly on downshifting I have tried all the exhaust modes any ideas.

 

[Stan Whitney]

On the other board I saw the turn down/turn away suggestions.
You could also use a plug/baffle on the inner pipes (where the valves are) - they are the straight through - lightly muffled pipe that makes the most noise.
Some of the newer tuning software like pcmtec can edit the active exhaust tables - eg keep the flaps fully closed at WOT in quiet mode
Use the grimspeed simulator modules to bypass the active exhaust and force the flaps closed

GrimmSpeed Exhaust Valve Simulator

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[Mad Hatter]

Oh boy!! you can get to 99 db!! Your lucky! Down here, for our biggest track, we have to go to a sound booth and measure no more then 90Db at 6000 rpm. Its all a art form to get your Db's down and not loose power. But it can be done.


Actually since Laguna has a 90db limit as well, You can see lots of people manage to get it done.

 

[Dave_W]

When talking sound limits, remember it's not only the decibel limit number, but also the weighting (typical A), response speed (slow or fast), and most importantly the distance between the source and meter. Doubling the distance reduces the sound level by 6dB.

 

[Mad Hatter]

When talking sound limits, remember it's not only the decibel limit number, but also the weighting (typical A), response speed (slow or fast), and most importantly the distance between the source and meter. Doubling the distance reduces the sound level by 6dB.

Very true! they measure us some 3m from the exhaust! Have gone to the booth with the rear muffler stuffed full of steel wool. Until I saw a rx7 with the same cheat catch fire....