The 24 Hours of Lemons Forums → Lemons Tech → How are exhaust noise levels measured?
Can you guys tell us how exhaust noise levels are measured?? We put a single cherry bomb on our car, and it's pretty damn loud still. I have a radio shack SPL meter, which definitely is nothing compared to the way the SCCA measures sound, but we're knocking at the door of 92dB according to it. Any suggestions?
Apparently a muffler turn-down or turn-up helps a lot by redirecting the sound into the concrete or into the sky. The sound may not actually be any quieter, but if nobody hears it, that doesn't matter.
There were black flags for noise at Toledo, but it was mainly because it is really obvious when your muffler falls off.
We ran a single glass-pak and turn down and were fine. The turn down makes a huge difference as the ground muffles some of the sound.
FWIW, I never saw them check ANY car at CMP for an inproper dB level.
Sound checking is usually done on some remote corner of the track, you likely wouldn't have noticed it if there was someone out there doing it.
I remember being black flagged for being too loud at Detroit(ish). Don't know if they actually had a meter or not, but they told us to button it up.
Personally, I think you're better off to just use your own ear. You've already said it's "loud". Make it "not loud". The 3 hp at 7,000 rpm you're going to lose by putting a proper muffler on the car ain't gonna kill you.
We ran a cherry bomb on our car at Altamont.
The sucker came off during the race and we immediately new it was our car.
Of course the driver didn't know and kept driving until they black flagged him 4 laps later. Some how he didn't hear us screaming at him over the radio.:D
They do work, and like everyone suggests pointing the tip down towards the ground does muffle the sound.
Thanks guys!
It's not really a HP issue, it's a "we had a cherry bomb laying around and don't want to buy a muffler" thing, haha. We'll turn down the exhaust and see how that helps.
Fuckin' spammers have found us.
So you mean he doesn't really want to be friends, and I don't look nice??? 
ha
I think he likes your car............
Maybe it's Pedobear getting on the forum!
Personally, I think you're better off to just use your own ear. You've already said it's "loud". Make it "not loud".
This is really the best summary--noise measurement varies from track to track, sometimes turndowns work, sometime they don't, etc....
If you want a cheap muffler, check the dumpster behind the muffler shop. Lotsa guys taking good-quality OEM stuff off for Flows and whistle tips.
Lotsa guys taking good-quality OEM stuff off for Flows and whistle tips.
Bubb Rubb goes "whoo whoo!"
We never got whistle tips in the midwest... do they still exist? The midwest does remember bubb rubb though...
LOL. We had to educate one of our teammates on Bubb Rub at the Lamest Day. He hadn't heard of that video before. Thank god verizon had good cell coverage in Amish country, we fired the video right up.
If you want a cheap muffler, check the dumpster behind the muffler shop. Lotsa guys taking good-quality OEM stuff off for Flows and whistle tips.
That is a sweet tip... don't know what I didn't think of that.. I am a scrounger from WAY back...
Thrush turbo mufflers are about $25 at Jegs and they quieted our Quad4 right down.
We never got whistle tips in the midwest... do they still exist? The midwest does remember bubb rubb though...
thay's just for deco-ray-shun.
THE WHISTLES GO WOO-WOOOOOOOOO!!!!!!!!!!
almost unrelated factoid:
DTM tips (those turned up rain catchers found on import 'racecars') were designed specifically for the purpose of getting around noise restrictions. the testing procedure puts the mic on the ground at tailpipe height, so it catches direct pipe noise AND reflected from the ground noise. DTM tips point the noise upwards and into the sky, missing the mic.
in my world, most of us have our ears located skyward when compared to tailpipes, so i'm not sure DTM tips will help the somewhat subjective 'that thing is too loud' call.
of course, leave it to japan to solve that problem as well.
totally unrelated:
while i was looking for the above pic, i found the following theme:
ready........go!
UGG... those crazy ass creations with their cardboard body kits and individual pipes for each cylinder... oh i loath them.
Ok that's getting added to the fiero...
We got an ultra thin CHerry Bomb 1-in 1-out erctangular muffler from Summit Racing for $22.95 to put on the 325. Got a scrap of pipe from Midas bent to make a side-exit exhaust ahead of the wheel (and well ahead of the fuel tank) and our exhaust was built for around $40 including the clamps, not including the new O2 sensor that didn't make our car run any better......
The cherry bomb is louder inside the car than outside it. we could hardly hear the car trackside at NL but it was fairly loud inside. I think the muffler is touching the floorpan, so that's likely where the nasty resonance is coming from.
DTM tips (those turned up rain catchers found on import 'racecars') were designed specifically for the purpose of getting around noise restrictions. the testing procedure puts the mic on the ground at tailpipe height, so it catches direct pipe noise AND reflected from the ground noise. DTM tips point the noise upwards and into the sky, missing the mic.
And, to bring things full circle, the intended effect of DTM tips can be skillfully avoided by LeMons-spec muffler hangers!
proof that even the best of ideas can be made better.
In our defense, the Ded Bull Golf came that way. We tightened up the clamps to keep everything from dragging and just ran it.
Granted this doesn't apply to the Fiero but say some one were to upturn their exhaust and weld a muffler directly to the header/manifold. Legal?!
i believe i noticed something in the rules about the exhaust exiting behind the driver/compartment.
edit:
3.26.1: Exhaust system may not dump ahead of the driver, and must not allow undue levels of exhaust to reach the driver's compartment.
so, if your car is rear engine, i guess you can try.
i believe i noticed something in the rules about the exhaust exiting behind the driver/compartment.
edit:
3.26.1: Exhaust system may not dump ahead of the driver, and must not allow undue levels of exhaust to reach the driver's compartment.so, if your car is rear engine, i guess you can try.
We already have the Fiero's exhaust worked out. I was just wondering for cars like an old crown vic or caprice... if they could do destruction derby style dumps through the hood... if they are tall enough the fumes and noise wouldn't reach the compartment.
The 24 Hours of Lemons Forums → Lemons Tech → How are exhaust noise levels measured?