[JLB_m235]

Hi guys, wondering for those that have done trackways with decibel limits what you've run?

I've currently got a Sports Cat (downpipe) and a Miltek race catback (with a valve) on my M235i and was hoping to do some trackdays but not sure if id have to put my standard exhaust back on for it as it is quite loud lol,
most of the tracks I'm looking at have 95-98 decibel limit at standstill and 102-105 drive by limit

[RacerBowie]

Originally Posted by JLB_m235

Hi guys, wondering for those that have done trackways with decibel limits what you've run?

I've currently got a Sports Cat (downpipe) and a Miltek race catback (with a valve) on my M235i and was hoping to do some trackdays but not sure if id have to put my standard exhaust back on for it as it is quite loud lol,
most of the tracks I'm looking at have 95-98 decibel limit at standstill and 102-105 drive by limit

If it is 102 dB driveby at 50ft (that measurement distance is the US "standard" but I see you're in the UK so maybe it's different) any street legal exhaust on a turbo car should be legal EXCEPT if you've got a lot of snapping and popping on decel, as those can sometimes trip a meter. There are exceptions (Camaros and Mustangs especially have "race" modes on factory exhausts that are over 100dB) but unless you're a crazy person you're not daily driving a car that's in danger of failing a 102 dB sound limit.

For reference dB are expressed as a logarithmic equation, not linear. So 98 at 50' is kind of loud, 100 at 50' is significantly louder, etc. In addition, atmospheric conditions (cloudy/overcast) can effect the measurements by as much at 2-3 dB from a known previous measurement.

Hope this helps.