Hive. Need some grassroots opinions as we have a track event scheduled in a month and trying to figure out the most sustainable approach to solving. Current car: 2018 ZL1. Current exhaust: 3" cat back race exhaust (broken off resonators): https://www.mbrp.com/collections/s7033al-mbrp-cat-back-exhaust-for-2023-chevrolet-camaro-zl1-6-2l-v8
Picture of one of the broken off resonators below, but the other has since broken off as well. I would love your opinion on some parts I could take to an exhaust shop to give us an option to go from mild (NCM) to wild (everywhere else). SuperTrapps have been considered with welding shut the location of the old resonator holes, but if I go with 2 supertrapps, any easy ideas to seal off the other two exhaust tip (one on each side)? What if I seal off all 4 exhaust tips and just leave the two small 2.25" outlets, think that would be an option to reduce sound enough and not kill the engine's 6XX hp? Not worried about max power, just dont want to hurt anything for the weekend.
More complicated approach would be adding a mulffer off of each of the old resonator spots with downturns and adding some sort of manual butterfly valve I can climb under the car to activate when at NCM? Open to cheapish ideas that should get me to 102.5dbs.
Bump in hopes of an exhaust hero.
Maybe cap the two resonator flanges (should be negligible performance impact because of how they branch off) and try with supertrapps or inserts in all 4 tips? If there's some headroom for more noise you could then try removing two of them.
May try something like these: https://www.summitracing.com/parts/pte-h3844
Mounted into 4 of these: https://www.speedwaymotors.com/Speedway-Turn-Down-Kickout-Tail-Pipe-Tips-3-1-2-x-10-Inch,29462.html
Then set screw them into my 4 tailpipes, if still too much noise, maybe add some stainless steel wool behind them? Would allow me to direct the noise away from T3 soundbooth a bit, make them easily removable, just hope they would dampen the noise sufficiently.
Yeah that looks like a solid plan, I expect the inserts and turndowns would do the job without any added packing.
Rodan
UltraDork
4/21/24 11:28 p.m.
When we had our '18 ZL1, we had to meet a 95db limit for one of our local tracks. The stock ZL1 'suitcase' muffler in 'race' mode was too loud, and the manual says not to run on the track without putting the exhaust in 'race' mode. I ended up putting V bands on the 'straight through' outlets and using a mandrel bend to direct the exhaust away from the sound meter, which was only on one side of the track. With the stock tips welded to a V band ring, they could easily be swapped back and forth. This worked for our use case, but may not if you have sound meters on both sides. Be cautious, as I've seen pics of melted bumpers from too restrictive mufflers... the ZL1 generates a LOT of exhaust heat.
Ordered 4 turndown tips and 4 spiral muffler inserts to try. Any advice on things to have on hand at the track if these dont quite meet requirements? Just stuff some steel wool behind them in varying amounts until it gets down far enough below 102dB?
Adding steel wool and turning all the tips away from the sound meters is about all you can do, it's a pretty safe assumption that you'll be below the limit with the 4 tips and inserts though.
