FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: CV355 on August 05, 2022, 08:02:15 AM
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The nearby city just put in a new sound ordinance bill, and now several surrounding towns are doing it too. People in the local Mustang club have been reporting that first time offenders are getting $1,080 fines. It's aimed at reducing hooning, which I understand, but some people are getting nailed even if they aren't hooning around. It got me thinking...
How much of the perceived "noise" is truly coming from the tailpipes on cars like ours? I've owned a few high-hp mod motors and coyotes with aggressive cams, and almost all of the volume was from the tailpipes (obviously all overhead cams...). But, with big pushrod engines with aggressive cams, it seems split between the engine bay and the tailpipes. I took a video of our Mach 1 just sitting there idling, and the tailpipes weren't that loud at idle but you could hear every pulse from the engine all around almost irrespective to exhaust. It's just something that hasn't occurred to me to really investigate before.
Changing out the cam in our FE is not something I really want to do at this time, but I am entertaining putting in quieter mufflers (2.5" Magnaflows right now), but I'm curious if it'll really have much of an effect. Any thoughts?
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The quietest mufflers I have used that perform well right now are Borla ProXS and Jones Full Boar, both are similar to the Magnaflow, but the Jones is the quietest.
As far as engine noise, although you may have some valvetrain, I'd say the open element air cleaners have the bark when you are in it. Modern cars go to great lengths to add silencers, I'd probably look there if the exhaust doesn't do it for you.
Of course as you eluded to, both of those are only real loud when you likely are doing something that you shouldn't anyway LOL I have a couple of 5.0s I work on, Big Mouth exhaust, and I try to tell the kids, fast guys don't want the noise because it draws attention. Of course to a young guy, that goes over like a lead balloon
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The quietest mufflers I have used that perform well right now are Borla ProXS and Jones Full Boar, both are similar to the Magnaflow, but the Jones is the quietest.
As far as engine noise, although you may have some valvetrain, I'd say the open element air cleaners have the bark when you are in it. Modern cars go to great lengths to add silencers, I'd probably look there if the exhaust doesn't do it for you.
Of course as you eluded to, both of those are only real loud when you likely are doing something that you shouldn't anyway LOL I have a couple of 5.0s I work on, Big Mouth exhaust, and I try to tell the kids, fast guys don't want the noise because it draws attention. Of course to a young guy, that goes over like a lead balloon
I didn't even think about the open air cleaner... I am running N/A at the moment, didn't even cross my mind. In 1-2 weeks, I should have the blower all set up and done, so after that it will have a carb hat and closed inlet all the way through to a filter in the fender area.
I have definitely crossed that threshold, and I'm starting to really prefer a more quiet exhaust. I still want to hear it, but if I can't drive it to Waffle House at 6am on a Sunday, it's probably too loud.
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Interesting. Here in my neck of the woods, cruising along even below say the 25 mph or 30 mph speed limit brings stares as due to engine and exhaust noise, neither bad btw, they think the car is going WAY over the speed limit. Untrue but that's what some think.
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In Sweden we have whats called Amature constructed vehicles
at first tech inspection they check sound level, 85Db. A stock Harley
have to much mecanical noice to pass. Same with hoodles hotrods with
overvalve engines have a hard time to pass
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If you want to quiet the exhaust, look into adding a resonator to your existing system. One thing that happens underhood with headers is that the exhaust pulse causes the primary header pipe to ring. Nothing you can do about that other than going to iron manifolds.
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In Sweden we have whats called Amature constructed vehicles
at first tech inspection they check sound level, 85Db. A stock Harley
have to much mecanical noice to pass. Same with hoodles hotrods with
overvalve engines have a hard time to pass
I would suspect my bone stock, 7.3L, IDI, diesel would fail this test too.
The engine in factory spec simply makes a lot of noise....no exhaust sounds, just the running engine.
What do they do when a factory delivered vehicle is too loud and it is not something like exhaust causing the noise?
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There are quite a few little things that can be done to tune your exhaust to be quieter, while using the same components.
Steel, stainless steel, titanium header pipe material, thickness, and diameter have an effect. Most headers use tubes that ting, or ring, with each exhaust pulse adding to the engine noise.
Exhaust pipe diameter, either too big or too small, will effect the overall sound.
Too small often causes a rapping, popping effect.
Too large often causes a drone, or echo effect.
Muffler location in the system makes a difference.
Close to the header collector means the gasses are still expanding after they exit the muffler.
Close to the tail pipe exit can often cause a quieter exhaust note.
Muffler and resonator, placed properly, will often decrease the exhaust tone.
Number and style of bends in the pipe, as well as pipe length can effect tone.
Tail pipe exit position, direction, and finish end make a difference too.
Exit under the car, before the rear axle and you get a lot of added sounds due to harmonics of the body of the car.
Exit directed at the ground causes the sound to bounce up and back, giving reflected sounds that are not part of the sound profile when the pipe is aimed out into open space.
A pipe exit with a straight cut will cause the exhaust gasses to pop out, like a smoke ring, giving a sharper tone as compared to a slash cut that allows the gas pulse to "slip" out more quietly.
Having a balance tube of some type (H-pipe, X-pipe, Merge-pipe) will lessen the overall pulse strength coming out of the pipes.
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I would suspect my bone stock, 7.3L, IDI, diesel would fail this test too.
The engine in factory spec simply makes a lot of noise....no exhaust sounds, just the running engine.
What do they do when a factory delivered vehicle is too loud and it is not something like exhaust causing the noise?
No doubt. Nothing is much louder than an IDI injection pump at idle.
CV355:
Make sure you understand the noise ordinance very clearly. The measurement location makes a huge difference. The difference between taking the measurement 1 ft from the tailpipe vs 4 ft can be 10 db or more. Sound pressure decreases with the square of distance.
More volume within the muffler generally helps a bunch. The extra volume lowers the sound register and reduces the pressure. When I first built my '62 Merc, I used the same glass pack muffler I had used on my '51 F-1. I figured the engines had similar displacements (351W vs. 352 FE), cam profiles, and exhaust tubing sizes, and I liked the sound that the '51 produced. I was way wrong. The FE in the Merc was LOUD! Like scare women and children, wife needs ear plugs in the car, get a ticket on 35E through St. Paul loud. I swapped in a pair of glasspacks that had much more volume and it mellowed the sound right out and knocked the volume down significantly.
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Like cleandan said, tailpipe exit direction can make quite a difference . On my 59 (428 with FPA headers, 2 1/2" pipes with Dyna Max "turbo" style mufflers) I didn`t really want the tail pipes sticking straight out below the rear bumper, so the exhaust builder made the tail pipes exit behind the rear tires, on a 45 degree angle, pointing downward, similar to how a late 60s Chevy Nova SS was. Inside the car, the exhaust sounds fairly loud, and it will blow the small stones in the driveway around, but there is an older bridge in town, with a deck of expanded metal, and when I drive the car over the bridge, the exhaust sound virtually dis appears, all you really hear is the tires running over the ventilated deck surface. Be interesting how the decibel numbers would compare if the probe was directed from straight behind the car, vs off to the sides. Or is the probe was pointed to wards the road surface.
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in my neck of the woods i feel pretty lucky,no noise ordinance.i run open headers on the street most of the time,but i do put my dynomax 3 inch straight thru mufflers on to go to a show or a meet a little ways off.. you should hear some of the harleys around here.i dont feel loud at all near them.
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LOL on noise. When I was asking for my variance to build the shop, I got asked about noise. One board member was concerned because he knew I had race cars. I answered "My SIL lives around the corner and has a Harley. There are two other Harley's about 5 houses away. None have mufflers as far as I can tell. They are tagged and licensed properly. My race cars all have mufflers." Pretty much ended that discussion.
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LOL on noise. When I was asking for my variance to build the shop, I got asked about noise. One board member was concerned because he knew I had race cars. I answered "My SIL lives around the corner and has a Harley. There are two other Harley's about 5 houses away. None have mufflers as far as I can tell. They are tagged and licensed properly. My race cars all have mufflers." Pretty much ended that discussion.
I too find the application of noise ordinance rules interesting.
A Harley Davidson motorcycle can be loud enough to be heard over 2 miles away and this seems to be the norm, as well as allowed.
If your customized Semi-Tractor is running 10" diameter, straight through stacks, and it resonates the windows in homes as it drives by, no worries, carry on, you are fine.
There are constant daily instances where the vehicle noise is very loud, yet little is done to enforce that law....and it becomes ignored, which sort of defeats the law.
If you enact a law you should be required to enforce that law evenly and consistently....otherwise get that law off the list.
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All good info in this thread, some things I hadn't considered.
in my neck of the woods i feel pretty lucky,no noise ordinance.i run open headers on the street most of the time,but i do put my dynomax 3 inch straight thru mufflers on to go to a show or a meet a little ways off.. you should hear some of the harleys around here.i dont feel loud at all near them.
My town has no noise ordinance. People drive around with open headers at 2am. It's just a small town out in the boonies, so even if Billy-Bob is rumbling along at 2am down the highway with open headers, it doesn't really wake you up. The city about 20ish miles away has really cracked down, and the town between is starting to push it too. So, if you get a craving for Waffle House and want to drive into town, you cross into the new sound ordinance. Some of the members of the local Mustang club have reported that the crackdown is pretty strict right now. My wife runs a 5.0 Coyote with a Borla ATAK exhaust, and that is not quiet at all. I'm surprised she hasn't been pulled over yet.
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Where is the town with the noise ordinance?