Remember when making noise and going fast didn't bother too many folks in town? You could stay on the outskirts of town or use a frontage road to test a new sway bar or brake pad compound. When you weren't looking, the town grew up all around you...everywhere. Now it's hard to find a deserted road where a little noise or speed won't get you thrown in jail. If you do load up the trailer and head out to a track for a mid week test, there could be a sound meter operator waiting to say " go home and get mufflers". All over the country race tracks and autocross events are required to keep the noise to new low decibel limits.
"Noise is your problem" he said "You'll have to go home and get mufflers and come back tomorrow."
Consider Laguna Seca Raceway in Monterey California. Once the site of Fort Ord Army Base; tanks, and artillery were right there with the Can-Am cars making all the good sounds we love to hear. Amid the sand dunes and rolling coastal hills the noise just didn't bother anyone. Today, year round camping and residential development has moved into the military facility. Laguna Seca is a modern beautiful race track with all the amenities, and of course, the dreaded SOUND METER is there too.
During the week or on a normal weekend the noise limit at Laguna Seca is 90 decibels at fifty feet. How noisy is that? One person suggested it's like a delivery truck driving by your house. Great.....how noisy is that? Noise standards are tough because they are a new thing to us racers. Also there are several variables. Some of the variables which affect noise are: weather and air density, surrounding structures and landscape, shape and construction of the race vehicle, then, too, each sound meter has it's own "ear personality".
If you have a noise problem, let's consider what's actually making the racket and how we might quiet things down a bit. Tin can bodies with no insulation are noisier than you might think. Intake systems can produce a lot of noise too. Primarily, it's those exhaust pipes that make the meter jump. Is your engine a four banger or a V-12 ? Does that V-8 have eight individual pipes or do they all converge into one huge collector and tail pipe? Cylinder firing order and manifolding all introduce variables into the noise equation. If your engine is a four valve design you'll be louder than a two valve engine of the same size. Pity the poor fellow with a rotary because he has noise and heat problems nobody can solve without a lot of work and money. God bless the turbocharger when it comes to noise; more power, free mufflering.
When your still mad about a black flag and insisting your car isn't THAT noisy its hard to really be objective, eventually though, it must be dealt with and there are many companies producing good free flow mufflers.
At this point I'd like to suggest you make a simple sketch of your car placing all the main parts in a "scale layout". This will give you some insight into available space and the relative distance between the important items. So here is your homework:
1) Be honest when you consider how serious Your noise problem is.
2) Note all the variables you can think of, ask all your buddies for help.
3) Use the phone, and find some tech articles on silencers.
4) Consider whether it might be time to redesign your entire exaust system front to rear.
5) Make that scale drawing of your entire car, noting availabe space for bigger, better, or more advanced design silencers.
6) Remember what Mom and Dad said: Have a budget!
7) Your professional engine builder will have some solutions, ask him.
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