3" header back into Borla is 100db - too loud
 

My custom 3" header-back single exhaust (normally aspirated) into a Borla muffler and straight tail pipe was measured at 100db at Thunderhill SCCA race in March. They gave me a caution, but that was all as the Thunderhill max is 103db. However, Laguna Seca is max 93db (even less during certain times). I know I can turn the tailpipe inwards (to the left) and reduce the measured sound pressure, but I don't believe it would knock it down 7db. I suspect I need to install a resonator or muffler in line.

Any suggestions on what I need to do to get my 3" header-back single exhaust and Borla muffler down to 93db and pass Laguna Seca?

Ultra quiet resonator. Doing the dolphin tip (pointing it to the ground like the J's or toda) can help as well. I would maybe try that first then add the resonator.

I used a Moroso spiral flow muffler when I had a custom 3" and it went from about 105 down to 97. Might be something to look into with the tip pointed away from the meter.

Thats asking a lot to go from 100 down to 92 or 90, I don't think its possible with just a simple elbow pipe but Ive seen guys with external mufflers and a pig tail looking thing with the tip pointed towards the driver side (away from the sound booth at Laguna). I would also think that pointing the elbow at the ground would make the car even louder, could be wrong though.

I've been considering trying something to make my EVS 70ssp + 70MM TP pass sound there but Im pretty discouraged now that theres even less 92bd days and much more 90db days. At this point I just run the stock exhaust with a TP and call it a day. Its annoying to swap every time I go to Laguna but at least then I know I won't have to go home early from an expensive track day or lift up the hill between 5 and 6 (where the sound booth is) which would suck.

Im curious to see what the finished product is and how loud it is if you decide to go forward with something. Hopefully there is a relatively simple solution so swapping exhausts becomes a thing of the past haha. Best of luck!

I have successfully run an ap2 + 70mm asm + berk 70mm hfc + k&n FIPK @ laguna at 4 events. I don't really even worry if it's 90 - 92 db. So far I haven't been flagged. I've been black flagged for numbers falling off more often than not

actually my miata had blown more black flags; as well my gsxrs (600 & 1000) with all factory I/H/E