Cheap_Thrills Posted March 16, 2009 Posted March 16, 2009 Anyone know how to test how loud an exhaust is before I hit the track and possibly get black flagged? I just installed a performance muffler, but I think it turned out to be an amplifier. I found some dB meters for $50 and up, but I thought there might be a way to test without spending money. All I can find are comparison charts for different sounds. They say a lawnmower at 3' is 90db, I guess I could have my kid mow the lawn, rev my motor and ask which one he can hear. Quote
Lucid Moments Posted March 16, 2009 Posted March 16, 2009 Its going to depend entirely on the track, and where they measure the sound. It will usually be somewhere on the longest straight so they get you at full throttle. You can tweak things a little to go with each track. Quote
edrock96GT Posted March 17, 2009 Posted March 17, 2009 I'm not sure about the track rules, but you can find out how close (or over) you are to your state laws and go from there. The tests are usually done at a distance of 50' generally in the direction the exhaust points while holding at (I believe) 3000 rpm. I think most limits are around 90db or a little more. It's been a few years since I learned how to do the test and can't guarantee the specific numbers, but that should at least help point you in the right direction. You'd be amazed at how loud it actually has to be to be illegal. I thought mine was and found out I was nowhere close. I imagine that even if you do go over the legal limit, you should still have a little cusion at the track. Hope this helps! Quote
Driver Posted March 17, 2009 Posted March 17, 2009 You could drag it to a DOT vehicle inspection station. If they can measure it to ticket you, they should be able to insect for it. Quote
Trevor57 Posted March 17, 2009 Posted March 17, 2009 If you have a resonator/muffler you are fine. Quote
Cheap_Thrills Posted March 17, 2009 Author Posted March 17, 2009 Well, it's a muffler, but a straight flow-through design, so I guess more like a glass-pack. Doesn't really "muffle" as much as changes the pitch. The track I was worried about was Infineon, 90dB limit. I don't know if they change the dB limit for IRL, NASCAR, Top Fuel cars that run there but my little 944 NA could never be that loud. But what's wierd, I've seen cars run what seemed like open pipes and have no problems, but also seen street legal DE cars like a Ford GT and Mustang get black flagged for noise. Maybe it's just a Ford thing. I won't worry about it. Quote
chuck schultz Posted March 18, 2009 Posted March 18, 2009 There are many variables that affect your sound readings as you pass the meter. Weather conditions, gear selection, how well you got out of the last corner, the direction of the exhaust outlet, state of tune, and, as the book says, "driver resolve," are some of them. Quote
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