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Calling all 1.8 mk7s with muffler deletes! (decibel readings)

MikeF1021

Ready to race!
Location
MA
I am considering keeping the resonator and deleting the muffler on my 1.8.

My local scca autocross locale has a strict sound limit of 90 db measured at 75 feet. The local track has a limit of 96 db, but they don't state from what distance(side of track, I guess). I understand that decibels are basically calculated with a logarithm that increases in a non-linear way, similar in effect to how earthquake magnitudes are calculated. So while a quiet library may be 30 decibels, and a jackhammer would be 90 db, the jackhammer is obviously waaay louder than 3x the sound of a library.

Annnnyyyways, the point I'm making is I understand that 90 decibels is really freaking loud.

It seems like a muffler delete wont make a dramatic decible difference on our cars, but will instead give them a much better exhaust tone. However, someday I will want a new downpipe and that would obviously change things...


Luckily it seems that there are plenty of free apps for sound meters available on Google play and in the app store. And judging by the reviews some of them are actually fairly accurate(within ~10%). Sure, probably not as accurate or precise as a pro decibel meter, but good enough to give us some reference points, perhaps.

So, I am hoping that those of you who have done any sort of exhaust modifications(but particularly muffler deletes) might be curious enough and kind enough to help me compile some data on how loud our pipes can really get.

I'm sure I will get plenty of "it's not that loud don't worry about it" responses, but I am enough of a nerd to appreciate some good(half baked) stats!

Anyone interested in downloading the app and having a friend record you from the side of the street while you redline your 1.8?
 

MikeF1021

Ready to race!
Location
MA
Thanks for the input! Its hard to have a frame of reference for db readings when distance is such a factor in their measurement.

The local autox spot is at an old airfield in Devens, MA. I guess the locals have been trying to get any sort of racing shut down for years but to no avail. The db limits keep things copacetic enough with the cranky neighbors to keep the autox events sustainable, I guess. The track is in Palmer, MA and I know the neighbors there complain as well. I wouldn't be surprised if the town is breathing down their neck to enforce the strict sound limit.

But yeah, I gave up on this crowd sourcing idea pretty quickly, and also gave up on the idea of a muffler delete.

I'm going with a downpipe and the oem catback. I'll add a resonator and/or upgrade the oem resonator if the drone is too much or if it is too loud for the guys at the local autox/track.
 
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MeltedSolid

Autocross Newbie
Location
San Francisco Bay Area
Car(s)
'15 Golf, e36 328i
When I first installed my IS20 my first drive was catback-less just because I was curious. I could disconnect the catback again and check the sound level. I remember it was crazy loud from inside the car as the exhaust outlet was right underneath the cabin, but it actually wasn't that loud from the outside. If that's near or below 90db then I bet there's little short of a complete straight pipe that would get you over the sound limits.

Also, is that 10% on the logarithmic scale or 10% on the absolute scale? Within 9 decibels isn't very useful but within 10% absolute is basically as accurate as anyone short of a scientist would ever need.
 

anjoVW

Ready to race!
Location
Killeen, TX
Any sound clips by any chance of a 1.8t with JUST a muffler delete (not resonator delete included)? I've only seen 1.8t's with resonator and muffler deletes, or GTI's with muffler deletes, but I'm not sure about if we'll actually sound the same as GTI's do with mufflers deleted.
 
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