Mudge Posted March 13, 2003 Share Posted March 13, 2003 I have twice pipes and a stock exaust manifold on my 73 240Z, the car is definately going to be louder @ WOT (aka WFO) than 90db, but I have the chance to run Laguna next month if I can do something about it. Does anyone have a muffler idea, or should I just run another muffler in the center? If I get black flagged for sound 3x I will get booted from the track, and that would be a waste of big moola. No I do not want a disk type muffler, too many horror stories. Most other adjustable mufflers cost way too much. Since the twice pipes route RIGHT under my damn rear end, I wouldn't mind ripping the setup off the car anyway and making up my own exaust, so I may do that, if I can do it reasonably inexpensively since I'm jogging multiple project here, on a budget of course. I do have a 280ZXT car, but I dont imagine I could steal that setup as with the downpipe/turbo setup it wont be the same dimensions as a 240Z NA car I imagine. Otherwise, I bet the muffler is relatively quiet, it looks either stock or low-performance, bah. Ideas for getting down to 90db or a tad less for safety? I dont expect to see more than maybe 6k RPM tops, I dont want to nuke the engine, especially since I dont know its timingchain /oilpump life. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 13, 2003 Author Share Posted March 13, 2003 http://www.howstuffworks.com/question124.htm A Lawnmower is apperantly 90db Quote Link to comment Share on other sites More sharing options...
Tim240z Posted March 13, 2003 Share Posted March 13, 2003 I would first see if in fact you will exceed the 90dB limit at the distance that the track measures from. I believe for highway regulations, the 90dB is measured at 20feet away from the car, from the side of the car. Maybe a trip to the local CHP inspection station can confirm you sound level (whoah, did I just sy that?!). Check with the track on their testing criteria. Most times they don't check at WOT, but at a lower RPM. Tim Quote Link to comment Share on other sites More sharing options...
yo2001 Posted March 13, 2003 Share Posted March 13, 2003 Borla XP Pro muffler is real quite. Quote Link to comment Share on other sites More sharing options...
clint78z Posted March 13, 2003 Share Posted March 13, 2003 I am not sure what you are referring to as a bad wrap on the disc type muffler. I have had a 3" SuperTrapp for 10+ years I absolutley love the sound of it on an L6. The packing lasted well and stainless is good quality. The only beef I have ever had was I left the bolts in too long over 5 years and broke 2 pulling it out. They have rebuild kits as well. Granted if you quiet them right up you might get better performance out of some other mufflers, but when you put on a bunch of discs they are quite effecient. Reports are that they provide a vacuum in some cases. I would highly recommend them to someone who wants adjustablity. On a normal muffler you can simply clamp in something to restrict noise if they are going to boot you. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 13, 2003 Author Share Posted March 13, 2003 Most times they don't check at WOT' date=' but at a lower RPM. [/quote'] They do, they are measuring at 2 points and I know for sure one point they will boot you if you are "obviously" short shifting or trying to fool the db meter in anyway, they are strict. I am not sure what you are referring to as a bad wrap on the disc type muffler. I have had a 3" SuperTrapp for 10+ years I absolutley love the sound of it on an L6. Your lucky. For people trying to pass Laguna sound regulations, one person had a blown exaust gasket (rotary spec racer), and one engine failure. Quote Link to comment Share on other sites More sharing options...
clint78z Posted March 13, 2003 Share Posted March 13, 2003 My doorhandle broke once when I had my Supertrapp on, that must have been the cause People have engine failures all the time especially at race tracks. Before I bought my muffler I read many articles on it, it was equal or above flow of any muffler out there. When you start cutting the noise, the backpressure does go up. There is quite a noticable difference in loudness it goes from super loud to bearable on long trips. If you are looking for a quiet muffler all the time with the best flow look else where, however it does what it is intended to do and I wouldn't buy a different one. The bad wrap is from ppl who look at the end cap and discs and it just looks wrong, when in fact it gives just as much flow as most performance mufflers. Perfhaps I will make a dyno run with discs and no discs, I doubt that there will be much differnce. Quote Link to comment Share on other sites More sharing options...
johnc Posted March 13, 2003 Share Posted March 13, 2003 Laguna Seca is tough for noise control because of where they measure the sound (between 5 & 6 and again between 6 & 7). You get sound reflection off the hillside and the Jersey walls. My BSP 240Z with a 2.5" exhaust, a Borla XR-1 Turbo, SUs, and ITG air filters registered 93db there and 90db when measured the next weekend at the SCCA Solo2 NT at Qualcom Stadium in San Diego. Switching to a single ITG air filter (instead of the dual setup) dropped the sound to 91db at Laguna and a 90 degree turn down exhaust tip got the sound to 89db. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 13, 2003 Author Share Posted March 13, 2003 People have engine failures all the time especially at race tracks. True, true... he said it started with the car running hotter than usual, either way, the backpressure it made to get the car to the db level required, I still believe that it does cause a direct problem. Other people run 2 mufflers inline (4 for dual exaust) and have no such blowouts of gaskets or unexpected heat issues. I already broke my drivers side handle! Damn twicepipes or just damn potmetal I was expecting to use a possible turndown yes, provided I of course get rid of my twice pipes setup completely. I suppose I could tape off portions of my dual weber filters if needed, they wont really be changeable though, they are the oval and maybe 2" tall filters that are standard for the downdraft setups. It looks like I could have 3.5 hours of track time! I just cannot pass that up. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 13, 2003 Author Share Posted March 13, 2003 It will be a usual GGLC event with too much track time, liberal passing rules in the slower group, and unlimited (safe) passing in the faster group. All drivers will be allowed to go out in both groups at their discrection and burn-through as much rubber as they please. IM GOING TO HAVE A HEART ATTACK! I'M THERE!!!!!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
Clifton Posted March 16, 2003 Share Posted March 16, 2003 Are all the Ca. tracks this strict on noise. What do they do when Cart races there? I've never heard of a db limit at a track or even on the street in Az. Quote Link to comment Share on other sites More sharing options...
johnc Posted March 16, 2003 Share Posted March 16, 2003 Laguna Seca is allowed a few over the limit races each year. Its the only track in California that I'm aware of that has a more restrictive limit then the standard 107db limit imposed on all racetracks in the US (usually by the sanctioning body - SCCA, NASA, etc.) But, noise restrictions are coming and will eventually be enforced on all racetracks. Not as severe as at Laguna, but you'll see noise monitiring and limits across thec ountry within 5 years. Its not a bad thing and cars can make good power when properly tuned for mufflers. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 16, 2003 Author Share Posted March 16, 2003 Yeah, cars with CATS and mufflers are making great power now, but anywho... it does depend on who you are, as to what DB limit is imposed at your event, us little guys get the shaft. Quote Link to comment Share on other sites More sharing options...
Clifton Posted March 16, 2003 Share Posted March 16, 2003 That's amazing, I never knew US tracks had db limits. I wasn't sure if it was some state law or just the track. Quote Link to comment Share on other sites More sharing options...
Mudge Posted March 16, 2003 Author Share Posted March 16, 2003 I assume its partly local law, and partly appeasing the locals. Thunderhill often has no limit until I believe 6PM, so I've run wide open exaust there before, and my Camaro pegged the meter at 125 db so I dont truly know how loud it was. Quote Link to comment Share on other sites More sharing options...
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